Absorption, Distribution and Excretion
**Oral Administration** Tramadol is administered as a racemate, with both the [-] and [+] forms of both tramadol and the M1 metabolite detected in circulation. Following administration, racemic tramadol is rapidly and almost completely absorbed, with a bioavailability of 75%. This difference in absorption and bioavailability can be attributed to the 20-30% first-pass metabolism. Peak plasma concentrations of tramadol and the primary metabolite M1 occur at two and three hours, respectively. Following a single oral dose of 100mg of tramadol, the Cmax was found to be approximately 300μg/L with a Tmax of 1.6-1.9 hours, while metabolite M1 was found to have a Cmax of 55μg/L with a Tmax of 3 hours. Steady-state plasma concentrations of both tramadol and M1 are achieved within two days of dosing. There is no evidence of self-induction. Following multiple oral doses, Cmax is 16% higher and AUC is 36% higher than after a single dose, demonstrating a potential role of saturable first-pass hepatic metabolism in increasing bioavailability. **Intramuscular Administration** Tramadol is rapidly and almost completely absorbed following intramuscular administration. Following injection of 50mg of tramadol, Cmax of 166μg/L was found with a Tmax of 0.75 hours. **Rectal Administration** Following rectal administration with suppositories containing 100mg of tramadol, Cmax of 294μg/L was found with a Tmax of 3.3 hours. The absolute bioavailability was found to be higher than oral administration (77% vs 75%), likely due to reduced first-pass metabolism with rectal administration compared to oral administration.
Tramadol is eliminated primarily through metabolism by the liver and the metabolites are excreted primarily by the kidneys, accounting for 90% of the excretion while the remaining 10% is excreted through feces. Approximately 30% of the dose is excreted in the urine as unchanged drug, whereas 60% of the dose is excreted as metabolites. The mean terminal plasma elimination half-lives of racemic tramadol and racemic M1 are 6.3 ± 1.4 and 7.4 ± 1.4 hours, respectively. The plasma elimination half-life of racemic tramadol increased from approximately six hours to seven hours upon multiple dosing.
The volume of distribution of tramadol is reported to be in the range of 2.6-2.9 L/kg. Tramadol has high tissue affinity; the total volume of distribution after oral administration was 306L and 203L after parenteral administration. Tramadol crosses the blood-brain barrier with peak brain concentrations occurring 10 minutes following oral administration. It also crosses the placental barrier with umbilical concentrations being found to be ~80% of maternal concentrations.
In clinical trials, the clearance rate of tramadol ranged from 3.73 ml/min/kg in renal impairment patients to 8.50 ml/min/kg in healthy adults.
The objective of this study was to determine the pharmacokinetics of two orally administered doses of tramadol (5 and 10 mg/kg) and its major metabolite (O-desmethyltramadol) (M1) in loggerhead sea turtles (Caretta caretta). After oral administration, the half-life of tramadol administered at 5 and 10 mg/kg was 20.35 and 22.67 hr, whereas the half-life of M1 was 10.23 and 11.26 hr, respectively. The maximum concentration (Cmax) for tramadol after oral administration at 5 mg/kg and 10 mg/kg was 373 and 719 ng/mL, whereas that of M1 was 655 and 1,376 ng/mL, respectively. Tramadol administered orally to loggerhead sea turtles at both dosages provided measurable plasma concentrations of tramadol and O-desmethyltramadol for several days with no adverse effects. Plasma concentrations of tramadol and O-desmethyltramadol remained >/= 100 ng/mL for at least 48 and 72 hr when tramadol was administered at 10 mg/kg.
The mean absolute bioavailability of a 100 mg oral dose is approximately 75%. The mean peak plasma concentration of racemic tramadol and M1 occurs at two and three hours, respectively, after administration in healthy adults. In general, both enantiomers of tramadol and M1 follow a parallel time course in the body following single and multiple doses although small differences (approximately 10%) exist in the absolute amount of each enantiomer present.
Tramadol is eliminated primarily through metabolism by the liver and the metabolites are eliminated primarily by the kidneys.
The aim of this study was to investigate the bioavailability of tramadol hydrochloride after oral admin of Tramadol--50 mg capsules, made in Synteza Pharmaceutical-Chemical Company in Poznan. As a reference preparation of Tramadol was used Tramal--50 mg capsules, (Grunenthal, Germany). The preparations were investigated in 20 healthy volunteers, according to a randomized two-way, cross-over design in the fasted state. Blood samples for determination of tramadol plasma concns were collected at pre-defined time points up to 24 hr following drug admin. A washout period of 1 wk separated both treatment periods. Tramadol plasma concns were determined by means of a validated HPLC method (fluorescence detector, verapamil as an internal standard). Values of 1,226.4 ng/hr/ml (Tramadol) & 1,397.01 ng/hr/ml (Tramal) for the parameter AUC(0-infinity) demonstrate a nearly identical extent of drug absorption. Max concns--Cmax (217.81 ng/ml & 246.0 ng/ml) & time to reach max plasma concn--Tmax (2.14 & 2.31 hr) achieved for Tramadol & reference preparation did not differ significantly. ... The bioavailability of tramadol hydrochloride after admin of Tramadol is the same as after admin of Tramal, whose clinical efficacy was tested before.
For more Absorption, Distribution and Excretion (Complete) data for TRAMADOL (20 total), please visit the HSDB record page.

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Metabolism / Metabolites
Tramadol undergoes extensive first-pass metabolism in the liver by N- and O- demethylation and conjugation. From the extensive metabolism, there have been identified at least 23 metabolites. There are two main metabolic pathways: the O-demethylation of tramadol to produce O-desmethyl-tramadol (M1) catalyzed by CYP2D6 and the N-demethylation to N-desmethyl-tramadol (M2) catalyzed by CYP3A4 and CYP2B6. The wide variability in the pharmacokinetic properties between patients can partly be ascribed to polymorphisms within the gene for CYP2D6 that determine its enzymatic activity. CYP2D6\*1 is considered the wild-type allele associated with normal enzyme activity and the "extensive metabolizer" phenotype; 90-95% of Caucasians are considered "extensive metabolizers" (with normal CYP2D6 function) while the remaining 5-10% are considered "poor metabolizers" with reduced or non-functioning enzyme. CYP2D6 alleles associated with non-functioning enzyme include *3, *4, *5, and *6 while alleles associated with reduced activity include *9, *10, *17, and *41. Poor metabolizers have reduced activity of the CYP2D6 enzyme and therefore less production of tramadol metabolites M1 and M2, which ultimately results in a reduced analgesic effect as tramadol interacts with the μ-opioid receptor primarily via M1. There are also large differences in the frequency of these alleles between different ethnicities: \*3, \*4, \*5, \*6, and \*41 are more common among Caucasians while \*17 is more common in Africans for example. Compared to 5-10% of Caucasians, only ~1% of Asians are considered poor metabolizers, however Asian populations carry a much higher frequency (51%) of the CYP2D6\*10 allele, which is relatively rare in Caucasian populations and results in higher exposure to tramadol. Some individuals are considered "ultra-rapid metabolizers", such as those carrying CYP2D6 gene duplications (CYP2D6*DUP) or multiplications. These individuals are at risk of intoxication or exaggerated effects of tramadol due to higher concentrations of its active metabolite (M1). The occurrence of this phenotype is seen in approximately 1% to 2% of East Asians (Chinese, Japanese, Korean), 1% to 10% of Caucasians, 3% to 4% of African-Americans, and may be >10% in certain racial/ethnic groups (ie, Oceanian, Northern African, Middle Eastern, Ashkenazi Jews, Puerto Rican). The FDA label recommends avoiding the use of tramadol in these individuals.
Tramadol is extensively metabolized after oral administration by a number of pathways, including CYP2D6 and CYP3A4, as well as by conjugation of parent and metabolites. Approximately 30% of the dose is excreted in the urine as unchanged drug, whereas 60% of the dose is excreted as metabolites. The remainder is excreted either as unidentified or as unextractable metabolites. The major metabolic pathways appear to be N- and O-demethylation and glucuronidation or sulfation in the liver. One metabolite (O-desmethyltramadol, denoted M1) is pharmacologically active in animal models. Formation of M1 is dependent on CYP2D6 and as such is subject to inhibition, which may affect the therapeutic response
Tramadol has as many as 11 metabolites. One metabolite (o-desmethyl tramadol, also called M1) may have greater opiate effects than the parent drug (for example, 200-300 times greater opiate effect than tramadol) but still lower than morphine. In animals that produce this metabolite in sufficient amounts, some analgesic action may be attributed to opiate-mediated effects from the active metabolite. The other metabolites have not been shown to have active analgesic activity.
Tramadol is extensively metabolized by a number of pathways, including CYP2D6 and CYP3A4, as well as by conjugation of parent metabolites. One metabolite, M1, is pharmacology active in animal models. The formation of M1 is dependent upon Cytochrome P-450(2D6) and as such is subject to both metabolic induction and inhibition which may affect the therapeutic response. /Salt not specified/
Tramadol is a synthetic opioid, widely used for post-surgical and chronic pain. Lethal overdose due only to tramadol is not common; more often the poisoning is due to tramadol in combination with other substances. Reported is a suicidal case of lethal tramadol poisoning in a 48-year-old woman. Tramadol and its metabolites O-desmethyltramadol (M1), N-desmethyltramadol (M2), N,N-didesmethyltramadol (M3), N,O-didesmethyltramadol (M5) were detected by GC/MS in biological fluids (femoral blood, bile, urine, gastric content) and viscera (brain, lung, liver and kidney). The tramadol concentration in femoral blood was 61.83 ug/mL which is approximately 30 times higher than that believed to be lethal. According with other Authors, a preferential formation of M1 over M2 (M1/M2 ratio >1) is indicative of acute death, while M1/M2 ratio <1 suggests that death occurred after a longer time lapse from ingestion.
Tramadol has known human metabolites that include O-desmethyl-tramadol and N-desmethyltramadol.
Hepatic. The major metabolic pathways appear to be N- and O- demethylation and glucuronidation or sulfation in the liver. One metabolite (O-desmethyltramadol, denoted M1) is pharmacologically active in animal models. CYP3A4 and CYP2B6 facilitates the biotransformation of tramadol to N-desmethyl-tramadol. CYP2D6 facilitates the biotransformation of tramadol to O-desmethyl-tramadol. Racemic tramadol is rapidly and almost completely absorbed after oral administration. The mean absolute bioavailability of a 100 mg oral dose is approximately 75%.The mean peak plasma concentration of racemic tramadol and M1 occurs at two and three hours, respectively, after administration in healthy adults. Tramadol undergoes hepatic metabolism via the cytochrome P450 isozyme CYP2D6, being O- and N-demethylated to five different metabolites. Of these, M1 (O-Desmethyltramadol) is the most significant since it has 200 times the affinity of (+)-tramadol, and furthermore has an elimination half-life of nine hours, compared with six hours for tramadol itself. In the 6% of the population that have slow CYP2D6 activity, there is therefore a slightly reduced analgesic effect. Phase II hepatic metabolism renders the metabolites water-soluble, which are excreted by the kidneys. Thus, reduced doses may be used in renal and hepatic impairment (A308, L1160).
Route of Elimination: Tramadol is eliminated primarily through metabolism by the liver and the metabolites are excreted primarily by the kidneys. Approximately 30% of the dose is excreted in the urine as unchanged drug, whereas 60% of the dose is excreted as metabolites.
Half Life: Tramadol and its metabolites are excreted primarily in the urine with observed plasma half-lives of 6.3 and 7.4 hours for tramadol and M1, respectively.

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Biological Half-Life
Tramadol reported a half-life of 5-6 hours while the M1 metabolite presents a half-life of 8 hours.
Healthy elderly subjects aged 65 to 75 years have plasma tramadol concentrations and elimination half-lives comparable to those observed in healthy subjects less than 65 years of age. In subjects over 75 years, maximum serum concentrations are elevated (208 vs. 162 ng/mL) and the elimination half-life is prolonged (7 vs. 6 hours) compared to subjects 65 to 75 years of age.
Metabolism of tramadol and M1 is reduced in patients with advanced cirrhosis of the liver, resulting in ... longer tramadol and M1 elimination half-lives (13 hr for tramadol and 19 hr for M1).
The mean terminal plasma elimination half-lives of racemic tramadol and racemic M1 are 6.3 +/- 1.4 and 7.4 +/- 1.4 hours, respectively. The plasma elimination half-life of racemic tramadol increased from approximately six hours to seven hours upon multiple dosing.
The objective of this study was to determine the pharmacokinetics of two orally administered doses of tramadol (5 and 10 mg/kg) and its major metabolite (O-desmethyltramadol) (M1) in loggerhead sea turtles (Caretta caretta). After oral administration, the half-life of tramadol administered at 5 and 10 mg/kg was 20.35 and 22.67 hr, whereas the half-life of M1 was 10.23 and 11.26 hr, respectively. ...
For more Biological Half-Life (Complete) data for TRAMADOL (9 total), please visit the HSDB record page.

Toxicity Summary
IDENTIFICATION AND USE: Tramadol is white, odorless crystalline powder with a bitter taste. Tramadol is an opioid analgesic which is indicated for the management of moderate to moderately severe pain in adults. In veterinary care, it may be used for the treatment of post-operative or chronic pain or cough. HUMAN EXPOSURE AND TOXICITY: Manifestations of overdosage are similar to those of other opiate agonists and include respiratory depression, lethargy, skeletal muscle flaccidity, coma, seizure, bradycardia, hypotension, cardiac arrest, miosis, vomiting, cold and clammy skin, cardiac collapse, and death. Serious and rarely fatal anaphylactoid reactions have been reported. Other reported hypersensitivity reactions include pruritus, urticaria, angioedema, bronchospasm, toxic epidermal necrolysis, and Stevens-Johnson syndrome. Potentially life-threatening serotonin syndrome may occur with tramadol, particularly with concurrent use of other serotonergic drugs, drugs that impair the metabolism of serotonin (e.g., MAO inhibitors), or drugs that impair the metabolism of tramadol (e.g., inhibitors of cytochrome P-450 [CYP] isoenzymes 2D6 and 3A4). The use of tramadol has been associated with an increased risk of hyponatremia requiring hospitalization. One study suggests a moderately increased risk of a teratogenic effect of tramadol. When tramadol is used during pregnancy, there is a serious risk for neonatal abstinence syndrome. ANIMAL STUDIES: There were 910 single agent exposures to tramadol reported to the ASPCA Animal Poison Control Center during 2009-2013. Of the 749 dogs, 142 were symptomatic. Symptoms included being sedated/lethargic, vomiting, tachycardic, vocalizing or ataxic, and agitated or tremoring. Of the 157 cats, 96 were symptomatic with symptoms such as having mydriasis, hypersalivating, lethargic, ataxic or tachycardic, and vomiting. Serotonin-reduced rats were predisposed to tramadol-induced seizures, and serotonin concentrations were negatively associated with seizure thresholds. Tramadol has been shown to be embryotoxic and fetotoxic in mice, rats, and rabbits at maternally toxic doses, but was not teratogenic at these dose levels. Tramadol was not mutagenic in the following assays: Ames Salmonella microsomal activation test, CHO/HPRT mammalian cell assay, mouse lymphoma assay (in the absence of metabolic activation), dominant lethal mutation tests in mice, chromosome aberration test in Chinese hamsters, and bone marrow micronucleus tests in mice and Chinese hamsters. Weakly mutagenic results occurred in the presence of metabolic activation in the mouse lymphoma assay and micronucleus test in rats. No carcinogenic effect of tramadol was observed in mice at oral doses up to approximately twice the MDHD of 400 mg/day for a 60 kg adult based on body surface conversion, for 26 weeks and in rats at oral doses up to approximately twice the MDHD for two years. A slight, but statistically significant, increase in two common murine tumors, pulmonary and hepatic, was observed in mice dosed orally up to 0.36 times the MDHD for approximately two years.
Tramadol and its O-desmethyl metabolite (M1) are selective, weak OP3-receptor agonists. Opiate receptors are coupled with G-protein receptors and function as both positive and negative regulators of synaptic transmission via G-proteins that activate effector proteins. As the effector system is adenylate cyclase and cAMP located at the inner surface of the plasma membrane, opioids decrease intracellular cAMP by inhibiting adenylate cyclase. Subsequently, the release of nociceptive neurotransmitters such as substance P, GABA, dopamine, acetylcholine and noradrenaline is inhibited. The analgesic properties of Tramadol can be attributed to norepinephrine and serotonin reuptake blockade in the CNS, which inhibits pain transmission in the spinal cord. The (+) enantiomer has higher affinity for the OP3 receptor and preferentially inhibits serotonin uptake and enhances serotonin release. The (-) enantiomer preferentially inhibits norepinephrine reuptake by stimulating alpha(2)-adrenergic receptors.

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Toxicity Data
LD50: 300-350 mg/kg (Oral, Rat) (A2833)

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Interactions
To investigate a possible antinociceptive role of serotonin receptor subtype 3 (5-HT(3)), we evaluated the effects of a coadmin of ondansetron, a 5-HT(3) selective antagonist, and tramadol, a central analgesic dependent on enhanced serotonergic transmission. Fifty-nine patients undergoing ear, throat, and nose surgery, using tramadol for 24-hr postoperative patient-controlled analgesia (bolus = 30 mg; lockout interval = 10 min) were randomly allocated either to a group receiving ondansetron continuous infusion (1 mg/mL/hr) for postoperative nausea and vomiting (Group O) or to a control group receiving saline (Group T). Pain & vomiting scores & tramadol consumption were evaluated at 4, 8, 12, and 24 hr. Pain scores were never >4, according to a 0-10 numerical rating scale, in both groups. Group O required significantly larger doses of tramadol at 4 hr (213 vs 71 mg, P<0.001), 8 hr (285 vs 128 mg, P<0.002), and 12 hr (406 vs 190 mg, P<0.002). Vomiting scores were higher in Group O at 4 hr (P<0.05) and 8 hr (P=0.05). We conclude that ondansetron reduced the overall analgesic effect of tramadol, probably blocking spinal 5-HT(3) receptors. ... Serotonin is an important neurotransmitter of the descending pathways that down-modulate spinal nociception. In postoperative pain, ondansetron, a selective 5-HT(3) receptor antagonist, increased the analgesic dose of tramadol. We suggest that, when antagonized for antiemetic purpose, 5-HT(3) receptors foster nociception, because of their site-dependent action.
The primary aims of this study were to assess the analgesic efficacy and adverse effects of single-dose oral tramadol plus acetaminophen in acute postoperative pain and to use meta-analysis to demonstrate the efficacy of the combination drug compared with its components. Individual patient data from 7 randomized, double blind, placebo controlled trials of tramadol plus acetaminophen were supplied for analysis by the R.W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey, USA. All trials used identical methods and assessed single-dose oral tramadol (75 mg or 112.5 mg) plus acetaminophen (650 mg or 975 mg) in adult patients with moderate or severe postoperative pain. Summed pain intensity and pain relief data over 6 and 8 hr and global evaluations of treatment effect after 8 hrs were extracted. Number-needed-to-treat (NNT) for one patient to obtain at least 50% pain relief was calculated. NNTs derived from pain relief data were compared with those derived from pain intensity data and global evaluations. Information on adverse effects was collected. Combination analgesics (tramadol plus acetaminophen) had significantly lower (better) NNTs than the components alone, and comparable efficacy to ibuprofen 400 mg. This could be shown for dental but not postsurgical pain, because more patients were available for the former. Adverse effects were similar for the combination drugs and the opioid component alone. Common adverse effects were dizziness, drowsiness, nausea, vomiting, and headache. In sum, this meta-analysis demonstrated analgesic superiority of the combination drug over its components, without additional toxicity.
A case report involving a 34-year-old white male who was found dead at home by his roommate is presented. At the time of his death, he was being treated with tramadol/acetaminophen, metaxalone, oxycodone, and amitriptyline. The decedent's mother stated that he had been taking increasing amounts of pain medication in order to sleep at night. There were no significant findings at autopsy; however, toxicology results supported a cause and manner of death resulting from suicidal mixed tramadol and amitriptyline toxicity. This case reports the tissue and fluid distribution of tramadol, amitriptyline, and their metabolites in an acutely fatal ingestion in an effort to document concentrations of these analytes in 12 matrices with respect to one another to assist toxicologists in difficult interpretations.
Tramadol has weak opioid properties, and an analgesic effect that is mediated mainly by inhibition of the reuptake of norepinephrine & serotonin (5-hydroxytryptamine [5-HT]) and facilitation of 5-HT release (1,2) at the spinal cord. Because 5-HT3 receptors play a key role in pain transmission at the spinal level (3), the 5-HT3 antagonist ondansetron may decr the efficacy of tramadol ... . In /a previous/ study, a small dose of 1 mg/kg tramadol was administered along with ondansetron 0.1 mg/kg or placebo, 15 min before the induction of anesthesia. Early postoperative pain scored differed significantly between the test groups. We therefore tested the hypothesis that the tramadol requirement by patient-controlled analgesia (PCA) may be increased when ondansetron is administered for antiemetic prophylaxis.
For more Interactions (Complete) data for TRAMADOL (24 total), please visit the HSDB record page.

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Non-Human Toxicity Values
LD50 Mouse oral 270 mg/kg /Tramadol hydrochloride/
LD50 Mouse sc 200 mg/kg /Tramadol hydrochloride/
LD50 Mouse iv 60.45 mg/kg /Tramadol hydrochloride/
LD50 Rat oral 228 mg/kg /Tramadol hydrochloride/
For more Non-Human Toxicity Values (Complete) data for TRAMADOL (6 total), please visit the HSDB record page.

Therapeutic Uses
Analgesics, Opioid; Narcotics
/CLINICAL TRIALS/ ClinicalTrials.gov is a registry and results database of publicly and privately supported clinical studies of human participants conducted around the world. The Web site is maintained by the National Library of Medicine (NLM) and the National Institutes of Health (NIH). Each ClinicalTrials.gov record presents summary information about a study protocol and includes the following: Disease or condition; Intervention (for example, the medical product, behavior, or procedure being studied); Title, description, and design of the study; Requirements for participation (eligibility criteria); Locations where the study is being conducted; Contact information for the study locations; and Links to relevant information on other health Web sites, such as NLM's MedlinePlus for patient health information and PubMed for citations and abstracts for scholarly articles in the field of medicine. Tramadol is included in the database.
Tramadol hydrochloride tablets, USP are indicated for the management of moderate to moderately severe pain in adults. /Included in US product label/
Tramadol hydrochloride extended-release tablets are indicated for the management of moderate to moderately severe chronic pain in adults who require around-the-clock treatment of their pain for an extended period of time.
MEDICATION (VET): Tramadol may be a useful alternative or adjunct for the treatment of post-operative or chronic pain or cough in dogs, cats and potentially, other species. When used in combination with nonsteroidal anti-inflammatory drugs (NSAIDs), or other analgesic drugs, (eg, amantadine, gabapentin, alpha-2 agonists) it may be particularly useful for chronic pain conditions.

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Drug Warnings
The U.S. Food and Drug Administration (FDA) is warning about several safety issues with the entire class of opioid pain medicines. These safety risks are potentially harmful interactions with numerous other medications, problems with the adrenal glands, and decreased sex hormone levels. We are requiring changes to the labels of all opioid drugs to warn about these risks. Opioids can interact with antidepressants and migraine medicines to cause a serious central nervous system reaction called serotonin syndrome, in which high levels of the chemical serotonin build up in the brain and cause toxicity. Taking opioids may lead to a rare, but serious condition in which the adrenal glands do not produce adequate amounts of the hormone cortisol. Cortisol helps the body respond to stress. Long-term use of opioids may be associated with decreased sex hormone levels and symptoms such as reduced interest in sex, impotence, or infertility.
In a continuing effort to educate prescribers and patients about the potential risks related to opioid use, the U.S. Food and Drug Administration today announced required class-wide safety labeling changes for immediate-release (IR) opioid pain medications. Among the changes, the FDA is requiring a new boxed warning about the serious risks of misuse, abuse, addiction, overdose and death. Today's actions are among a number of steps the agency recently outlined in a plan to reassess its approach to opioid medications. The plan is focused on policies aimed at reversing the epidemic, while still providing patients in pain access to effective relief.
FDA is investigating the use of the pain medicine tramadol in children aged 17 years and younger, because of the rare but serious risk of slowed or difficult breathing. This risk may be increased in children treated with tramadol for pain after surgery to remove their tonsils and/or adenoids. FDA is evaluating all available information and will communicate final conclusions and recommendations to the public when the review is complete. Tramadol is not FDA-approved for use in children; however, data show it is being used "off-label" in the pediatric population. Health care professionals should be aware of this and consider prescribing alternative FDA-approved pain medicines for children.
At recommended dosages, tramadol generally is well tolerated. Adverse effects usually have been mild and similar in incidence to active controls (i.e., acetaminophen 300 mg with codeine phosphate 30 mg and aspirin 325 mg with codeine phosphate 30 mg). The frequency of some adverse effects may be related to dose and route of administration. The most common adverse effects observed with tramadol in controlled clinical trials and open-label extension periods enrolling patients with chronic nonmalignant pain were nervous system effects (e.g., dizziness) and GI disturbances.
For more Drug Warnings (Complete) data for TRAMADOL (40 total), please visit the HSDB record page.

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Pharmacodynamics
Tramadol modulates the descending pain pathways within the central nervous system through the binding of parent and M1 metabolite to μ-opioid receptors and the weak inhibition of the reuptake of norepinephrine and serotonin. Apart from analgesia, tramadol may produce a constellation of symptoms (including dizziness, somnolence, nausea, constipation, sweating and pruritus) similar to that of other opioids. **Central Nervous System** In contrast to [morphine], tramadol has not been shown to cause histamine release. At therapeutic doses, tramadol has no effect on heart rate, left-ventricular function or cardiac index. Orthostatic hypotension has been observed. Tramadol produces respiratory depression by direct action on brain stem respiratory centres. The respiratory depression involves both a reduction in the responsiveness of the brain stem centres to increases in CO2 tension and to electrical stimulation. Tramadol depresses the cough reflex by a direct effect on the cough centre in the medulla. Antitussive effects may occur with doses lower than those usually required for analgesia. Tramadol causes miosis, even in total darkness. Pinpoint pupils are a sign of opioid overdose but are not pathognomonic (e.g., pontine lesions of hemorrhagic or ischemic origin may produce similar findings). Marked mydriasis rather than miosis may be seen with hypoxia in the setting of oxycodone overdose. Seizures have been reported in patients receiving tramadol within the recommended dosage range. Spontaneous post-marketing reports indicate that seizure risk is increased with doses of tramadol above the recommended range. Risk of convulsions may also increase in patients with epilepsy, those with a history of seizures or in patients with a recognized risk for seizure (such as head trauma, metabolic disorders, alcohol and drug withdrawal, CNS infections), or with concomitant use of other drugs known to reduce the seizure threshold. Tramadol can cause a rare but potentially life-threatening condition resulting from concomitant administration of serotonergic drugs (e.g., anti-depressants, migraine medications). Treatment with the serotoninergic drug should be discontinued if such events (characterized by clusters of symptoms such as hyperthermia, rigidity, myoclonus, autonomic instability with possible rapid fluctuations of vital signs, mental status changes including confusion, irritability, extreme agitation progressing to delirium and coma) occur and supportive symptomatic treatment should be initiated. Tramadol should not be used in combination with MAO inhibitors or serotonin-precursors (such as L-tryptophan, oxitriptan) and should be used with caution in combination with other serotonergic drugs (triptans, certain tricyclic antidepressants, lithium, St. John’s Wort) due to the risk of serotonin syndrome. **Gastrointestinal Tract and Other Smooth Muscle** Tramadol causes a reduction in motility associated with an increase in smooth muscle tone in the antrum of the stomach and duodenum. Digestion of food in the small intestine is delayed and propulsive contractions are decreased. Propulsive peristaltic waves in the colon are decreased, while tone may be increased to the point of spasm resulting in constipation. Other opioid-induced effects may include a reduction in gastric, biliary and pancreatic secretions, spasm of the sphincter of Oddi, and transient elevations in serum amylase. **Endocrine System** Opioids may influence the hypothalamic-pituitary-adrenal or -gonadal axes. Some changes that can be seen include an increase in serum prolactin and decreases in plasma cortisol and testosterone. Clinical signs and symptoms may be manifest from these hormonal changes. Hyponatremia has been reported very rarely with the use of tramadol, usually in patients with predisposing risk factors, such as elderly patients and/or patients using concomitant medications that may cause hyponatremia (e.g., antidepressants, benzodiazepines, diuretics). In some reports, hyponatremia appeared to be the result of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) and resolved with discontinuation of tramadol and appropriate treatment (e.g., fluid restriction). During tramadol treatment, monitoring for signs and symptoms of hyponatremia is recommended for patients with predisposing risk factors. **Cardiovascular** Tramadol administration may result in severe hypotension in patients whose ability to maintain adequate blood pressure is compromised by reduced blood volume, or concurrent administration of drugs such as phenothiazines and other tranquillizers, sedative/hypnotics, tricyclic antidepressants or general anesthetics. These patients should be monitored for signs of hypotension after initiating or titrating the dose of tramadol. **QTc-Interval Prolongation** The maximum placebo-adjusted mean change from baseline in the QTcF interval was 5.5 ms in the 400 mg/day treatment arm and 6.5 ms in the 600 mg/day mg treatment arm, both occurring at the 8h time point. Both treatment groups were within the 10 ms threshold for QT prolongation. Post-marketing experience with the use of tramadol containing products included rare reports of QT prolongation reported with an overdose. Particular care should be exercised when administering tramadol to patients who are suspected to be at an increased risk of experiencing torsade de pointes during treatment with a QTc-prolonging drug. **Abuse and Misuse** Like all opioids, tramadol has the potential for abuse and misuse, which can lead to overdose and death. Therefore, tramadol should be prescribed and handled with caution. **Dependence/Tolerance** Physical dependence and tolerance reflect the neuroadaptation of the opioid receptors to chronic exposure to an opioid and are separate and distinct from abuse and addiction. Tolerance, as well as physical dependence, may develop upon repeated administration of opioids, and are not by themselves evidence of an addictive disorder or abuse. Patients on prolonged therapy should be tapered gradually from the drug if it is no longer required for pain control. Withdrawal symptoms may occur following abrupt discontinuation of therapy or upon administration of an opioid antagonist. Some of the symptoms that may be associated with abrupt withdrawal of an opioid analgesic include body aches, diarrhea, gooseflesh, loss of appetite, nausea, nervousness or restlessness, anxiety, runny nose, sneezing, tremors or shivering, stomach cramps, tachycardia, trouble with sleeping, unusual increase in sweating, palpitations, unexplained fever, weakness and yawning.

C16H25NO2

263.37

263.188

27203-92-5

33741

Typically exists as solid at room temperature

178-181 °C
180 - 181 °C

2.6

1

3

4

19

282

2

CN(C)C[C@H]1CCCC[C@@]1(C2=CC(=CC=C2)OC)O

TVYLLZQTGLZFBW-ZBFHGGJFSA-N

InChI=1S/C16H25NO2/c1-17(2)12-14-7-4-5-10-16(14,18)13-8-6-9-15(11-13)19-3/h6,8-9,11,14,18H,4-5,7,10,12H2,1-3H3/t14-,16+/m1/s1

(1R,2R)-2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexan-1-ol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)