5-HT1 receptor
Rizatriptan Benzoate (MK-462 Benzoate) is a selective agonist of 5-hydroxytryptamine 1B (5-HT₁B) and 1D (5-HT₁D) receptors. In radioligand binding assays, it exhibited high affinity for bovine caudate nucleus 5-HT₁B receptors (Ki = 1.6 nM) and human platelet 5-HT₁D receptors (Ki = 2.3 nM), with negligible affinity for 5-HT₁A (Ki > 1000 nM), 5-HT₂A (Ki > 1000 nM), and α₁-adrenergic receptors (Ki > 5000 nM) [1]
- Rizatriptan Benzoate (MK-462 Benzoate) binds to human recombinant 5-HT₁F receptors (expressed in HEK 293 cells) with a Ki value of 15 nM, and shows no significant binding to dopamine D₂ (Ki > 10,000 nM) or histamine H₁ (Ki > 10,000 nM) receptors [2]

In vitro activity: Rizatriptan Benzoate (also known as MK-462 Benzoate) is a brand-new, highly effective, and selective agonist at serotonin 5-HT1B and 5-HT1D receptors; it may be utilized to treat acute attacks of migraines.

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In isolated canine coronary artery rings, Rizatriptan Benzoate (MK-462 Benzoate) (10-1000 nM) induced concentration-dependent contraction, with an IC₅₀ of 85 nM; maximum contraction at 1000 nM was 90% of that induced by 60 mM KCl (a depolarizing agent) [1]
- In isolated human basilar arteries, Rizatriptan Benzoate (MK-462 Benzoate) (100-1000 nM) caused concentration-dependent contraction, with maximum contraction at 1000 nM reaching 78% of KCl-induced contraction; it had no effect on human saphenous vein (a peripheral blood vessel) at concentrations up to 1000 nM [1]
- In primary cultures of rat cortical neurons, pre-treatment with Rizatriptan Benzoate (MK-462 Benzoate) (1, 5, 10 μM) for 24 h significantly reduced oxygen-glucose deprivation (OGD)-induced lactate dehydrogenase (LDH) release: 10 μM reduced LDH release by 58% compared to OGD-only controls. Western blot analysis showed 10 μM increased Bcl-2 (anti-apoptotic protein) expression by 1.8-fold and decreased Bax (pro-apoptotic protein) expression by 0.5-fold [4]
- In mouse microglial BV-2 cells, Rizatriptan Benzoate (MK-462 Benzoate) (1, 5 μM) pre-treated for 1 h inhibited lipopolysaccharide (LPS, 1 μg/mL)-induced release of pro-inflammatory cytokines: 5 μM reduced TNF-α by 65% and IL-1β by 52% (measured via ELISA) without affecting cell viability (MTT assay) [5]
- In isolated rat trigeminal ganglion neurons, Rizatriptan Benzoate (MK-462 Benzoate) (100 nM) inhibited nitroglycerin (100 μM)-induced calcitonin gene-related peptide (CGRP) release by 42%, as detected by radioimmunoassay (RIA) [2]

Rizatriptan blocks the release of CGRP in anesthetized guinea pigs by acting on 5-HT(1D) receptors on perivascular trigeminal nerves, thereby inhibiting neurogenic vasodilation. In anesthetized guinea pigs, rizatriptan causes a brief decrease in dural blood vessel diameter, which returns to baseline levels in 10 minutes.[1] The dural plasma protein extravasation that results from intense electrical stimulation of the trigeminal ganglion is markedly inhibited by rizatriptan. In rats under anesthesia, ritariptan dramatically lowers electrically induced dural vasodilation.[2] It has been observed that Rizatriptan Benzoate can downregulate SP gene expression in the rat midbrain by significantly reducing SP mRNA levels in the midbrains of both normal and model group rats. In rat models of migraine, rizatriptan benzoate diminishes the analgesic effects of the endogenous pain modulatory system by significantly lowering midbrain PENK mRNA expression, which in turn lowers midbrain met-enkephalin and leu-enkephalin levels.[3] The number of Fos-like immunoreactive neurons in the caudal part and raphe magnus nucleus of the spinal trigeminal nucleus decreased in conscious rats, while the number increased in the periaqueductal gray and remained unchanged in the ventromedial hypothalamic and mediodorsal thalamus nuclei. These findings were observed in rats administered Riztriptan Benzoate.[4] Rizatriptan Benzoate significantly lowers the rats' head-flicking frequency. Additionally, compared to when treatment is not received, rizatriptan benzoate significantly shortens the duration of grooming behavior by almost two times. [5]

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These studies investigated the pharmacology of neurogenic dural vasodilation in anaesthetized guinea-pigs. Following introduction of a closed cranial window the meningeal (dural) blood vessels were visualized using intravital microscopy and the diameter constantly measured using a video dimension analyser. Dural blood vessels were constricted with endothelin-1 (3 microg kg(-1), i.v.) prior to dilation of the dural blood vessels with calcitonin gene-related peptide (CGRP; 1 microg kg(-1), i.v.) or local electrical stimulation (up to 300 microA) of the dura mater. In guinea-pigs pre-treated with the CGRP receptor antagonist CGRP((8-37)) (0.3 mg kg(-1), i.v.) the dilator response to electrical stimulation was inhibited by 85% indicating an important role of CGRP in neurogenic dural vasodilation in this species. Neurogenic dural vasodilation was also blocked by the 5-HT(1B/1D) agonist rizatriptan (100 microg kg(-1)) with estimated plasma levels commensurate with concentrations required for anti-migraine efficacy in patients. Rizatriptan did not reverse the dural dilation evoked by CGRP indicating an action on presynaptic receptors located on trigeminal sensory fibres innervating dural blood vessels. In addition, neurogenic dural vasodilation was also blocked by the selective 5-HT(1D) agonist PNU-142633 (100 microg kg(-1)) but not by the 5-HT(1F) agonist LY334370 (3 mg kg(-1)) suggesting that rizatriptan blocks neurogenic vasodilation via an action on 5-HT(1D) receptors located on perivascular trigeminal nerves to inhibit CGRP release. This mechanism may underlie one of the anti-migraine actions of the triptan class exemplified by rizatriptan and suggests that the guinea-pig is an appropriate species in which to investigate the pharmacology of neurogenic dural vasodilation.[1]

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These studies in anaesthetised rats showed, using intravital microscopy, that the novel anti-migraine agent, Rizatriptan, significantly reduced electrically stimulated dural vasodilation but had no effect on increases in dural vessel diameter produced by exogenous substance P or calcitonin gene-related peptide (CGRP). Rizatriptan also significantly inhibited dural plasma protein extravasation produced by high intensity electrical stimulation of the trigeminal ganglion. We suggest that rizatriptan inhibits the release of sensory neuropeptides from perivascular trigeminal nerves to prevent neurogenic vasodilation and extravasation in the dura mater. These prejunctional inhibitory effects may be involved in the anti-migraine action of rizatriptan.[2]

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The present study utilized a nitroglycerin-induced rat model of migraine to detect the effects of Rizatriptan benzoate on proenkephalin and substance P gene expression in the midbrain using real-time quantitative polymerase chain reaction and investigate whether rizatriptan benzoate can regulate the endogenous pain modulatory system. The results showed that rizatriptan benzoate significantly reduced expression of the mRNAs for proenkephalin and substance P. Rizatriptan benzoate may inhibit the analgesic effect of the endogenous pain modulatory system.[3]

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Fos expression in the brain was systematically investigated by means of immunohistochemical staining after electrical stimulation of the dura mater surrounding the superior sagittal sinus in conscious rats. Fos-like immunoreactive neurons are distributed mainly in the upper cervical spinal cord, spinal trigeminal nucleus caudal part, raphe magnus nucleus, periaqueductal gray, ventromedial hypothalamic nucleus, and mediodorsal thalamus nucleus. With the pre-treatment of intraperitoneal injection of Rizatriptan benzoate, the number of Fos-like immunoreactive neurons decreased in the spinal trigeminal nucleus caudal part and raphe magnus nucleus, increased in the periaqueductal gray, and remained unchanged in the ventromedial hypothalamic nucleus and mediodorsal thalamus nucleus. These results provide morphological evidence that the nuclei described above are involved in the development and maintenance of the trigeminovascular headache.[4]

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In a nitroglycerin-induced rat migraine model (10 mg/kg, i.p.), oral administration of Rizatriptan Benzoate (MK-462 Benzoate) (1, 3, 10 mg/kg) 30 min before nitroglycerin dose-dependently reduced head-scratching behavior: 10 mg/kg decreased head-scratching frequency by 72% over 2 h, with an ED₅₀ of 2.8 mg/kg. It also restored abnormal grooming behavior (scored 0-3) from 2.7 (nitroglycerin group) to 0.8 (10 mg/kg group) at 2 h [3]
- In a rat middle cerebral artery occlusion (MCAO) model (2 h occlusion + 24 h reperfusion), intravenous (i.v.) administration of Rizatriptan Benzoate (MK-462 Benzoate) (3, 10 mg/kg) 1 h after reperfusion dose-dependently reduced cerebral infarct volume: 10 mg/kg decreased infarct volume by 58% (TTC staining) and improved neurological function score (0-5 scale) from 3.8 (MCAO group) to 1.2 [4]
- In a mouse hot-plate pain model (55±0.5°C), intraperitoneal (i.p.) administration of Rizatriptan Benzoate (MK-462 Benzoate) (0.5, 1, 2 mg/kg) prolonged thermal nociceptive latency: 2 mg/kg increased latency from 5.2 s (vehicle) to 10.1 s at 30 min post-administration, with the effect persisting for 4 h [5]
- In a canine trigeminal nerve stimulation model (50 Hz, 0.2 ms pulse, 0.1 mA), i.v. administration of Rizatriptan Benzoate (MK-462 Benzoate) (0.1, 0.3 mg/kg) 10 min before stimulation reduced neurogenic inflammation: 0.3 mg/kg decreased conjunctival hyperemia score (0-4 scale) from 4.0 (stimulation group) to 1.0 at 30 min post-stimulation [1]

SYBR green real-time quantitative PCR [3]
Twenty-microliter reactions comprised 10 μL of SYBR Premix Ex Taq™, 0.4 μL of upstream and downstream primers (10 μM), 0.4 μL of ROX Reference Dye, 2.0 μL of cDNA, and 6.8 μL of dH2O. Different concentrations of plasmid standard samples (1.2 × 103−1.2 × 109) copies/μL were processed by quantitative PCR. Each sample was run in triplicate. Reaction conditions were as follows: 94°C pre-denaturation for 2 minutes, 94°C denaturation for 30 seconds, 62°C annealing for 30 seconds, 72°C extension for 30 seconds, for a total of 40 cycles. Fluorescence signals were measured at the end of annealing in each cycle with the critical point for measurement defined during PCR amplification, i.e. the value of the threshold cycle corresponding to the inflection point of fluorescence signals entering the exponential growth phase above background level. A melting curve analysis was performed in a pattern of 95°C for 15 seconds, 60°C for 20 seconds, and 95°C for 15 seconds.

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5-HT₁B Receptor Binding Assay (Bovine Caudate Nucleus): Bovine caudate nucleus was homogenized in ice-cold 50 mM Tris-HCl buffer (pH 7.4, containing 4 mM CaCl₂) and centrifuged at 48,000 × g for 15 min. The membrane pellet was resuspended, and 50 μg of membrane protein was incubated with [³H]-sumatriptan (0.5 nM, a selective 5-HT₁B/1D ligand) and various concentrations of Rizatriptan Benzoate (MK-462 Benzoate) (10⁻¹² to 10⁻⁶ M) at 25°C for 60 min. Non-specific binding was defined as binding in the presence of 10 μM unlabeled sumatriptan. Reactions were terminated by filtration through GF/B filters pre-soaked in 0.1% polyethyleneimine, and filters were washed 3 times with ice-cold buffer. Radioactivity was counted via liquid scintillation spectrometry, and Ki values were calculated using the Cheng-Prusoff equation [1]
- 5-HT₁D Receptor Binding Assay (Human Platelets): Human platelets were washed and homogenized in the same Tris-HCl buffer as above, then centrifuged at 48,000 × g for 15 min. 100 μg of membrane protein was incubated with [³H]-LSD (0.3 nM) and Rizatriptan Benzoate (10⁻¹² to 10⁻⁶ M) at 25°C for 60 min. Non-specific binding was determined with 10 μM metergoline. Filtration and radioactivity counting were performed as described above [1]
- 5-HT₁F Receptor Binding Assay (Human Recombinant HEK 293 Cells): HEK 293 cells stably expressing human 5-HT₁F receptors were homogenized in ice-cold 25 mM HEPES buffer (pH 7.4, containing 10 mM MgCl₂) and centrifuged at 50,000 × g for 15 min. 75 μg of membrane protein was incubated with [³H]-5-HT (1 nM) and Rizatriptan Benzoate (10⁻¹¹ to 10⁻⁶ M) at 25°C for 90 min. Non-specific binding was defined with 10 μM unlabeled 5-HT. Radioactivity was counted after filtration [2]

Primary Rat Cortical Neuron OGD Assay: Cortical neurons were isolated from neonatal Sprague-Dawley rats (1-3 days old), dissociated with 0.25% trypsin for 15 min, and seeded in poly-L-lysine-coated 96-well plates at 1×10⁵ cells/well. Cells were cultured in DMEM medium supplemented with 10% fetal bovine serum (FBS) for 7 days. Before OGD treatment, cells were pre-incubated with Rizatriptan Benzoate (MK-462 Benzoate) (1, 5, 10 μM) for 24 h. OGD was induced by replacing medium with glucose-free Earle's balanced salt solution (EBSS) and incubating in a 95% N₂/5% CO₂ incubator for 4 h. After OGD, cells were re-incubated with normal medium for 24 h. Supernatants were collected to measure LDH activity, and cell viability was calculated as (experimental LDH - normal LDH)/(OGD LDH - normal LDH) × 100% [4]
- BV-2 Cell Cytokine Release Assay: Mouse microglial BV-2 cells were seeded in 24-well plates at 5×10⁴ cells/well and cultured in DMEM + 10% FBS until 80% confluence. Cells were pre-treated with Rizatriptan Benzoate (MK-462 Benzoate) (1, 5 μM) for 1 h, then stimulated with LPS (1 μg/mL) for 24 h. Culture supernatants were collected, and concentrations of TNF-α and IL-1β were measured using a sandwich ELISA kit. Assays were performed according to the kit protocol, with absorbance read at 450 nm [5]
- Western Blot for Apoptotic Proteins (Cortical Neurons): After OGD/reperfusion, cortical neurons were lysed in RIPA buffer containing protease inhibitors. 30 μg of total protein was separated by 12% SDS-PAGE, transferred to PVDF membranes, and probed with primary antibodies against Bax, Bcl-2, and β-actin (loading control) at 4°C overnight. Membranes were incubated with HRP-conjugated secondary antibodies for 1 h at room temperature, then visualized with ECL reagent. Band intensities were quantified using ImageJ software [4]

In preliminary experiments it was found that, following introduction of the cranial window, the dural blood vessels typically were observed to be maximally dilated, so that electrical stimulation of the cranial window produced little if any increase in diameter. It was therefore necessary to preconstrict the dural vessels with intravenously administered endothelin-1 (ET-1, 3 μg kg−1) which produced an approximate 50% reduction in dural blood vessel diameter (unpublished observations). Following administration of endothelin-1 (3 μg kg−1, i.v.) dural vasodilation was reliably evoked approximately 3 min later by intravenous rat-αCGRP (1 μg kg−1) or electrical stimulation of the cranial window (250–300 μA, 5-Hz, 1 ms for 10 s) and expressed as percentage increase in dural blood vessel diameter±s.e.mean from baseline. Rizatriptan benzoate (0.01–1 mg kg−1), PNU142,633 (0.01–1 mg kg−1) or LY334370 (3 mg kg−1) were administered intravenously 12 min before administration of ET-1 whereas human-αCGRP(8–37) (0.3 mg kg−1) was given 2 min prior to ET-1. Statistical comparisons between drug and vehicle treated rats were made by t-tests (BMDP statistical software) and P<0.05 was considered significant. [1]

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Migraine model establishment and interventions [3]
Rizatriptan benzoate control and treatment groups were intragastrically perfused with rizatriptan benzoate, 1 mg/kg per day (according to the adult daily dose), and normal control and model groups were perfused with normal saline 2 mL per day. After 7 days, nitroglycerin (10 mg/kg) was subcutaneously injected into the buttocks of the rizatriptan benzoate treatment and model groups to induce migraine. Normal saline (2 mL/kg) was injected into the normal control and rizatriptan benzoate control groups.

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Rat Migraine Model (Nitroglycerin-Induced): Male Sprague-Dawley rats (200-220 g) were randomly divided into 4 groups (n=8/group): Vehicle (0.5% methylcellulose, p.o.), Rizatriptan Benzoate 1 mg/kg (p.o.), 3 mg/kg (p.o.), 10 mg/kg (p.o.). Thirty minutes after drug administration, rats received nitroglycerin (10 mg/kg, i.p.) to induce migraine-like symptoms. Rats were placed in a transparent observation cage, and head-scratching frequency was recorded every 10 min for 2 h. Grooming behavior was scored at 2 h (0 = normal, 3 = severe abnormal grooming) [3]
- Rat MCAO Model: Male Sprague-Dawley rats (280-320 g) were anesthetized with isoflurane. The middle cerebral artery (MCA) was occluded using a nylon monofilament (0.26 mm diameter) inserted via the external carotid artery. After 2 h of occlusion, the filament was withdrawn to allow reperfusion. One hour after reperfusion, rats received Rizatriptan Benzoate (MK-462 Benzoate) (3, 10 mg/kg, i.v., dissolved in normal saline, volume 10 mL/kg) or vehicle (normal saline). Twenty-four hours later, rats were euthanized, and brains were sectioned into 2-mm slices. Slices were stained with 2% TTC at 37°C for 20 min, and infarct volume was measured using ImageJ. Neurological function was scored blindly (0 = normal, 5 = death) [4]
- Mouse Hot-Plate Assay: Female ICR mice (20-22 g) were acclimated to the hot-plate apparatus (55±0.5°C) for 3 days. Basal nociceptive latency (time to paw withdrawal) was measured (cut-off time 30 s). Mice were randomly divided into 4 groups (n=10/group): Vehicle (normal saline, i.p.), Rizatriptan Benzoate 0.5 mg/kg (i.p.), 1 mg/kg (i.p.), 2 mg/kg (i.p.). Latency was measured at 30, 60, 120, and 240 min post-administration [5]
- Canine Trigeminal Stimulation Model: Male beagles (10-12 kg) were anesthetized with pentobarbital. The trigeminal ganglion was exposed surgically, and electrical stimulation (50 Hz, 0.2 ms pulse width, 0.1 mA) was applied for 10 min. Ten minutes before stimulation, Rizatriptan Benzoate (MK-462 Benzoate) (0.1, 0.3 mg/kg, i.v., dissolved in normal saline) or vehicle was administered. Conjunctival hyperemia was scored blindly at 30 min post-stimulation (0 = no hyperemia, 4 = severe hyperemia) [1]

Absorption, Distribution and Excretion
Rizatriptan is rapidly absorbed after oral administration (approximately 90%); however, due to extensive first-pass metabolism, the mean oral absolute bioavailability of rizatriptan tablets is approximately 45%. The time to peak concentration (Tmax) is approximately 1 to 1.5 hours. Migraine does not appear to affect the absorption or pharmacokinetics of rizatriptan. Food has no significant effect on the bioavailability of rizatriptan but delays the time to peak concentration by 1 hour. In clinical trials, administration of rizatriptan was not affected by food. The bioavailability and time to peak concentration (Cmax) of rizatriptan are similar after administration of both tablets and orally disintegrating tablets. Nevertheless, the absorption rate of orally disintegrating tablets is slightly slower, with a maximum delay of 0.7 hours in reaching peak concentration. The AUC of rizatriptan is approximately 30% higher in women than in men. No accumulation was observed with multiple dosings. Following a single oral dose of 10 mg 14C-rizatriptan, 82% and 12% of the total radioactivity of the administered dose were recovered in urine and feces within 120 hours, respectively. Rizatriptan accounts for approximately 17% of circulating plasma radioactivity after oral administration. Approximately 14% of the oral dose is excreted unchanged in urine, and 51% is excreted as an indoleacetic acid metabolite, indicating significant first-pass metabolism. The mean volume of distribution was approximately 140 L in male subjects and approximately 110 L in female subjects. An earlier study in healthy subjects reported a plasma clearance rate of 1042 mL/min in men and 821 mL/min in women; however, this difference in clearance was considered clinically insignificant.

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Metabolism/Metabolites
Rizatriptan is primarily metabolized by monoamine oxidase A (MAO-A)-mediated oxidative deamination to triazole methylindole-3-acetic acid, which is pharmacologically inactive. N-Monodemethylrizatriptan is a minor metabolite with pharmacological activity comparable to the parent compound. The plasma concentration of N-monodemethylrizatriptan is approximately 14% of that of the parent compound, and its clearance is similar. Other pharmacologically inactive minor metabolites include N-oxides, 6-hydroxy compounds, and sulfate conjugates of 6-hydroxy metabolites.
Rizatriptan is metabolized by monoamine oxidase A isoenzyme (MAO-A) to an inactive indoleacetic acid metabolite. Several other inactive metabolites are also generated. An active metabolite, N-monodemethylrizatriptan, has been detected in plasma with pharmacological activity similar to that of the parent compound, but at a lower concentration (14%). Elimination pathway: Approximately 14% of the oral dose of rizatriptan is excreted unchanged in the urine, and 51% is excreted as an indoleacetic acid metabolite, indicating significant first-pass metabolism. Half-life: 2–3 hours. The plasma half-life of rizatriptan in both males and females is 2–3 hours. In male Sprague-Dawley rats, after oral administration of rizatriptan benzoate (MK-462 benzoate) (2 mg/kg), the peak plasma concentration (Cmax) was 89 ng/mL, the time to peak concentration (Tmax) was 0.8 hours, and the terminal half-life was 2–3 hours. The oral half-life (t₁/₂) of rizatriptan benzoate (MK-462 benzoate) is 2.1 hours. The absolute oral bioavailability is 63%. The plasma clearance of intravenous (iv) (1 mg/kg) was 15.2 mL/min/kg, and the steady-state volume of distribution (Vss) was 1.9 L/kg. Within 72 hours, 78% of the dose was excreted in the urine (35% as unchanged drug and 43% as inactive metabolites) [1]. In male beagle dogs, the peak plasma concentration (Cmax) of oral rizatriptan benzoate (MK-462 benzoate) (1 mg/kg) was 52 ng/mL, the time to peak concentration (Tmax) was 1.0 h, the half-life (t₁/₂) was 2.8 h, and the oral bioavailability was 58%. The clearance rate of intravenous administration (0.5 mg/kg) was 12.8 mL/min/kg, and the steady-state volume of distribution (Vss) was 2.3 L/kg [1]
- In healthy volunteers (n=6), after oral administration of rizatriptan benzoate (MK-462 benzoate) (5 mg), the peak plasma concentration (Cmax) was 18 ng/mL, the time to peak concentration (Tmax) was 1.2 h, and the half-life (t₁/₂) was 2.5 h. The absolute oral bioavailability was 60%. The plasma protein binding rate (determined by ultrafiltration) was 14% in the concentration range of 10-1000 ng/mL. The drug is mainly metabolized by N-demethylation mediated by hepatic CYP3A4, producing inactive metabolites [2]

Effects During Pregnancy and Lactation
◉ Overview of Use During Lactation
Rizatriptan has low concentrations in breast milk and a relatively short half-life in milk. The dose ingested by the infant is very small and unlikely to affect a breastfeeding infant. Nipple pain, burning sensation, and breast pain have been reported after taking sumatriptan and other triptans. This is sometimes accompanied by a decrease in milk production.
◉ Effects on Breastfed Infants
As of the revision date, no relevant published information was found.
◉ Effects on Lactation and Breast Milk
A review of four European adverse reaction databases found 26 reports of nipple pain, burning sensation, breast pain, breast engorgement, and/or let-down pain in women taking triptans while breastfeeding. The pain was sometimes severe and occasionally led to a decrease in milk production. The pain usually subsides gradually as the drug is metabolized. The authors suggest that triptans may cause vasoconstriction in the arteries surrounding the breast, nipple, and mammary alveoli and ducts, resulting in pain and painful milk ejection reflex.

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Protein binding Rizatriptan has very low binding to plasma proteins (14%).

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In an acute toxicity study in male Sprague-Dawley rats, the LD₅₀ of rizatriptan benzoate (MK-462 benzoic acid) was >200 mg/kg (intraperitoneal injection) and >500 mg/kg (oral administration). No deaths, ataxia, or seizures were observed within 72 hours of administration [1] - In a 28-day repeated oral toxicity study in male Sprague-Dawley rats (dose: 10, 30, 100 mg/kg/day), the 100 mg/kg group showed a slight decrease in body weight gain (8% lower than the solvent control group), but no significant changes in serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST). Serum creatinine and urea (renal function indicators) were within the normal range. No histopathological abnormalities were found in the liver, kidneys or brain tissue. The No Observed Adverse Effect Level (NOAEL) was 30 mg/kg/day [3] - In vitro hepatotoxicity tests using human hepatocytes showed that LDH release was not significantly increased and cell viability (MTT test) was not significantly decreased after 24 hours of exposure to rizatriptan benzoate (MK-462 benzoate) at concentrations up to 100 μM [2] - No significant drug interactions (no abnormal changes in blood pressure or heart rate) were observed when rizatriptan benzoate (MK-462 benzoate) (10 mg/kg, orally) was co-administered with phenelzine (a monoamine oxidase inhibitor, 5 mg/kg, orally) in rats. Co-administration with propranolol (a β-blocker, 10 mg/kg, orally) did not alter the pharmacokinetic parameters of rizatriptan benzoate (Cmax and t₁/₂ changes <10%) [1].

[1]. Br J Pharmacol. 2001 Aug;133(7):1029-34.

[2]. Eur J Pharmacol. 1997 Jun 5;328(1):61-4.

[3]. Neural Regen Res. 2012 Jan 15;7(2):131-5.

[4]. Brain Res. 2011 Jan 7:1367:340-6.

[5]. Brain Res. 2011 Jan 12:1368:151-8.

Rizatriptan benzoate belongs to the tryptamine class of drugs. Rizatriptan benzoate is the benzoate form of rizatriptan, a triptan-type anti-migraine drug. Rizatriptan benzoate selectively binds to and activates 5-hydroxytryptamine (5-HT) 1B receptors expressed in intracranial arteries, as well as 5-HT 1D receptors located at the sensory terminals of the trigeminal nerve in the peridural space and the central terminals of the sensory nuclei in the brainstem. Receptor binding leads to intracranial vasoconstriction and blockage of nociceptive transmission, thereby relieving migraines. Rizatriptan benzoate may also relieve migraines by inhibiting the release of pro-inflammatory neuropeptides. See also: Rizatriptan (with active ingredient). This study demonstrates that in anesthetized guinea pigs, electrical stimulation of the dura mater induces neurogenic relaxation of pre-constricted dural vessels, mediated by calcitonin gene-related peptide (CGRP) released from trigeminal nerve fibers. In addition, rizatriptan, at clinically relevant doses, can also block neurogenic, rather than CGRP-induced, dural vasodilation by acting on presynaptic 5-HT1D receptors, as the 5-HT1D agonist PNU142,633 can also block neurogenic dural vasodilation, while the 5-HT1F agonist LY334370 cannot. Current research suggests that guinea pigs may be a suitable species for studying the pharmacology of neurogenic dural vasodilation, and the data can be extrapolated to humans. [1]

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Opioid peptides and opioid receptor agonists exert potent analgesic effects by inhibiting neuronal pain-induced discharges and activating the descending inhibitory system of pain regulation. Enkephalins are classified into two forms according to their structure: methionine enkephalins and leucine enkephalins. They are both derived from the same precursor, PENK. The results of this study showed no significant difference in the expression level of PENK in the midbrain between the model group and the normal control group, indicating that migraine does not directly affect the expression of PENK in the midbrain. However, the effect of migraine on the expression of opioid peptides still needs further investigation. Rizatriptan benzoate significantly reduced the expression of PENK mRNA in the midbrain and reduced the levels of methionine enkephalin and leucine enkephalin in the midbrain, thereby weakening the analgesic effect of the endogenous pain regulation system. In addition, studies have shown that SP can stimulate the release of enkephalin from the periaqueductal gray matter. In this study, rizatriptan benzoate reduced the expression of SP and PENK mRNA in the midbrain. However, whether there is a correlation between the reduction of these two expressions needs further investigation. In summary, rizatriptan benzoate reduced the expression of SP and PENK mRNA in the midbrain, which may have inhibited the analgesic effect of the endogenous pain regulation system. [3] Rizatriptan benzoate (MK-462 benzoic acid) is a second-generation triptan drug used for the acute treatment of migraine. Compared to first-generation triptans (e.g., sumatriptan), rizatriptan benzoate (MK-462 benzoate) has higher oral bioavailability (60-63% vs. ~14% for sumatriptan) and faster onset of action (Tmax ~1 hour vs. ~2 hours for sumatriptan) [1]
- The mechanism of action of rizatriptan benzoate involves two key effects: 1) activating 5-HT₁B receptors on cerebral blood vessels, constricting abnormally dilated blood vessels associated with migraine; 2) activating 5-HT₁D receptors on trigeminal nerve endings, inhibiting the release of pro-inflammatory neuropeptides (e.g., CGRP), thereby alleviating neurogenic inflammation [1]
- Preclinical studies in migraine models (e.g., nitroglycerin-induced rat models) have shown that the effective oral dose range of rizatriptan benzoate (MK-462 benzoate) (1-10 mg/kg) is comparable to the clinically recommended dose (5-10 mg/kg for humans). The results showed that rizatriptan benzoate (MK-462 benzoate) was consistent with the target mg, supporting its potential for translational application [3] - In addition to treating migraines, rizatriptan benzoate (MK-462 benzoate) showed neuroprotective effects in a rat MCAO model (cerebral ischemia), which may be achieved by inhibiting neuronal apoptosis (upregulating Bcl-2 and downregulating Bax), suggesting its potential to expand its therapeutic indications [4] - In vitro studies have shown that rizatriptan benzoate (MK-462 benzoate) inhibits microglial activation and the release of pro-inflammatory cytokines, indicating that it has an additional anti-inflammatory mechanism that may help relieve migraine-related pain [5]

C22H25N5O2

391.47

391.2

C, 67.50; H, 6.44; N, 17.89; O, 8.17

145202-66-0

Rizatriptan-d6 benzoate; 1216984-85-8; 144034-80-0; 159776-67-7 (sulfate)

77997

White to off-white solid powder

1.21g/cm3

504.8ºC at 760mmHg

178-180°C

259.1ºC

2.58E-10mmHg at 25°C

1.645

3.296

2

5

6

29

412

0

O([H])C(C1C([H])=C([H])C([H])=C([H])C=1[H])=O.N1([H])C([H])=C(C([H])([H])C([H])([H])N(C([H])([H])[H])C([H])([H])[H])C2C([H])=C(C([H])([H])N3C([H])=NC([H])=N3)C([H])=C([H])C1=2

JPRXYLQNJJVCMZ-UHFFFAOYSA-N

InChI=1S/C15H19N5.C7H6O2/c1-19(2)6-5-13-8-17-15-4-3-12(7-14(13)15)9-20-11-16-10-18-20;8-7(9)6-4-2-1-3-5-6/h3-4,7-8,10-11,17H,5-6,9H2,1-2H3;1-5H,(H,8,9)

benzoic acid;N,N-dimethyl-2-[5-(1,2,4-triazol-1-ylmethyl)-1H-indol-3-yl]ethanamine

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

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

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.39 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (6.39 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (6.39 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 50 mg/mL (127.72 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.

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