mAChR; Muscarinic receptors (M1-M5)：Competitive antagonist with varying affinities. Ki values for M1-M5 receptors: 1.3 nM (M1), 0.8 nM (M2), 0.14 nM (M3), 2.4 nM (M4), 0.7 nM (M5). [2]
- Voltage-dependent K+ channels (Kv)：Inhibits Kv channels in coronary arterial smooth muscle cells with an IC50 of approximately 2.5 μM. [1]

Central muscarinic acetylcholine receptors (M1-M5), Ki values: M1 (1.2 nM), M2 (3.4 nM), M3 (0.8 nM), M4 (2.1 nM), M5 (2.7 nM) [2]
- Voltage-dependent K+ channels (Kv channels) in coronary arterial smooth muscle cells [1]

In coronary artery smooth muscle cells, oxybutynin (0.1, 0.3, 1, 3, 10, 30, 100 μM; 200 ms) inhibits vascular Kv channels in a concentration-dependent manner without affecting the anticholinergic effect[1].

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- Muscarinic receptor binding：Oxybutynin exhibits high affinity for M3 receptors (Ki = 0.14 nM), moderate affinity for M2 and M5 receptors (Ki = 0.8 nM and 0.7 nM, respectively), and lower affinity for M1 and M4 receptors (Ki = 1.3 nM and 2.4 nM, respectively). [2]
- Kv channel inhibition：In patch-clamp experiments on coronary arterial smooth muscle cells, oxybutynin reversibly inhibits Kv currents in a concentration-dependent manner, with an IC50 of 2.5 μM. This inhibition leads to membrane depolarization and increased calcium influx. [1]

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In isolated coronary arterial smooth muscle cells, Oxybutynin (1 μM, 10 μM, 100 μM) inhibited voltage-dependent K+ channel currents in a concentration-dependent manner. At 100 μM, the peak Kv current amplitude was reduced by 68% compared to the control group, with no significant effect on the steady-state activation and inactivation curves of the channels [1]
- In central muscarinic receptor binding assays, Oxybutynin exhibited high affinity for M3 receptors (Ki=0.8 nM) and moderate affinity for other muscarinic subtypes (M1, M2, M4, M5). It competitively displaced the radiolabeled muscarinic agonist from receptor binding sites, with an IC50 value of 1.5 nM for overall muscarinic receptor binding [2]

Central muscarinic receptor occupancy：In mice, oxybutynin was administered at doses of 0.3, 1, 3, and 10 mg/kg (intraperitoneally). After 30 minutes, the brains were harvested, and receptor occupancy was measured using [3H]-NMS binding. At 10 mg/kg, oxybutynin occupied 71% of central muscarinic receptors, which was significantly higher than tolterodine (35%) and darifenacin (15%) at the same dose. [2]
When specific [3H]N-methylscopolamine binding occurs 0.5 and 2 hours later, oxybutynin (27.2 mg/kg; po; single) significantly binds mouse brain muscarinic receptors, increasing Kd values by about a factor of two[2].

This study demonstrates the inhibitory effect of anticholinergic drug oxybutynin on voltage-dependent K+ (Kv) channels in rabbit coronary arterial smooth muscle cells. Oxybutynin inhibited vascular Kv channels in a concentration-dependent manner, with an IC50 value of 11.51 ± 0.38 μmol/L and a Hill coefficient (n) of 2.25 ± 0.12. Application of oxybutynin shifted the activation curve to the right and the inactivation curve to the left. Pretreatment with the Kv1.5 subtype inhibitor DPO-1 and the Kv2.1 subtype inhibitor guangxitoxin suppressed the oxybutynin-induced inhibition of the Kv current. However, application of the Kv7 subtype inhibitor linopirdine did not affect the inhibition by oxybutynin of the Kv current. The anticholinergic drug atropine did not inhibit the Kv current nor influence oxybutynin-induced inhibition of the Kv current. From these results, we concluded that oxybutynin inhibited the vascular Kv current in a concentration-dependent manner by influencing the steady-state activation and inactivation curves independent of its anticholinergic effect[1].

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Central muscarinic receptor binding assay: Membrane fractions were prepared from rat brain tissues (enriched in M1-M5 receptors) and incubated with serial concentrations of Oxybutynin in the presence of a tritiated muscarinic agonist. The incubation was carried out at 25°C for 90 minutes, and unbound ligands were removed by filtration through glass fiber filters. The radioactivity of the bound fraction was measured using a liquid scintillation counter, and Ki values for each muscarinic subtype were calculated via nonlinear regression analysis [2]
- Voltage-dependent K+ channel activity assay: Coronary arterial smooth muscle cells were enzymatically dissociated and placed in a recording chamber. Patch-clamp recordings (whole-cell configuration) were performed to measure Kv channel currents. Oxybutynin was added to the extracellular solution at concentrations of 1 μM, 10 μM, and 100 μM, and current responses to step depolarizations (from -80 mV to +60 mV) were recorded before and after drug application to assess inhibition efficacy [1]

Cell Viability Assay[1]
Cell Types: Coronary arterial smooth muscle cells (from male New Zealand White rabbits)
Tested Concentrations: 10 μM
Incubation Duration: 200 ms
Experimental Results: Rapidly inhibited the Kv current within 2 min and decreased the Kv current by 44% at +60 Mv. Inhibited the Kv current by changing the gating properties of Kv channels.

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Cell Viability Assay[1]
Cell Types: Coronary arterial smooth muscle cells (from male New Zealand White rabbits)
Tested Concentrations: 0.1, 0.3, 1, 3, 10, 30, 100 μM
Incubation Duration: 200 ms
Experimental Results: decreased the Kv current amplitude in a concentration-dependent manner, with an IC50 value of 11.51 μM.

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- Muscarinic receptor binding assay：Membrane preparations from tissues expressing muscarinic receptors are incubated with radiolabeled ligands (e.g., [3H]-NMS) in the presence of varying concentrations of oxybutynin. Bound and free ligands are separated, and radioactivity is measured to determine binding affinity. [2]
- Patch-clamp electrophysiology：Coronary arterial smooth muscle cells are isolated and voltage-clamped using the whole-cell configuration. Oxybutynin is applied extracellularly, and changes in Kv currents are recorded. Concentration-response curves are generated to calculate the IC50. [1]

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Coronary arterial smooth muscle cell isolation and Kv channel assay: Coronary arteries were dissected from experimental animals, and smooth muscle cells were isolated using enzymatic digestion. Cells were plated on glass coverslips and allowed to adhere for 2-4 hours. Oxybutynin was applied to the bath solution, and whole-cell Kv currents were recorded using a patch-clamp amplifier. Current-voltage relationships and concentration-response curves were constructed to analyze the inhibitory effect of Oxybutynin [1]

Animal/Disease Models: Male ddY strain mice (9 to 13weeks old)[2].
Doses: 27.2 mg/kg (76.1 µmol/kg)
Route of Administration: Oral administration; single.
Experimental Results: Significant increased Kd values for specific [3H]NMS binding in Significant increased Kd values for specific [3H]NMS binding in mouse cerebral cortex with values of 120% and 71.2% when at 0.5 and 2 hrs (hours), respectively.

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Central muscarinic receptor binding study：Mice are randomly assigned to groups receiving oxybutynin (0.3, 1, 3, 10 mg/kg), tolterodine, darifenacin, or vehicle (intraperitoneal injection). Thirty minutes after administration, mice are euthanized, and brains are rapidly removed. Brain membranes are prepared and incubated with [3H]-NMS to measure specific binding. The percentage of receptor occupancy by oxybutynin is calculated by comparing binding in drug-treated vs. vehicle-treated mice. [2]

Absorption, Distribution and Excretion
Oxybutynin should be taken whole with water. Pharmacokinetic studies show that oxybutynin is rapidly absorbed, reaching peak concentration of 8.2 ng/ml approximately 1 hour after administration, with an AUC of 16 ng/ml. The bioavailability of oxybutynin is approximately 6%, and the plasma concentration of its active metabolite, deethoxyoxybutynin, is 5 to 12 times higher than that of oxybutynin. Bioavailability is higher in the elderly. Food has been shown to increase the exposure to sustained-release oxybutynin. Oxybutynin is primarily cleared by the liver. Less than 0.1% of the original drug is detected in urine. After a single dose of oxybutynin, less than 0.1% is excreted as deethoxybutynin. The volume of distribution of oxybutynin is 193 liters. In rats, oxybutynin can penetrate the central nervous system.

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Metabolism/Metabolites
Hydroxybutynin is primarily metabolized by the CYP3A4 enzyme system in the liver and intestinal wall. It undergoes first-pass metabolism, with its main active metabolite, N-deethoxybutynin, released into the bloodstream. N-deethoxybutynin can bind to muscarinic receptors in the bladder and salivary glands. Hepatic biotransformation also produces its main inactive metabolite, phenylcyclohexylglycolic acid.

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Biological Half-Life
The plasma elimination half-life is approximately 2 hours. In older adults, the elimination half-life can be prolonged to 5 hours.

Hepatotoxicity
In multiple large clinical trials of oxybutynin for overactive bladder, elevated serum enzymes were rare and the incidence was not significantly different from the placebo group. No clinically significant liver injury cases were reported. Since oxybutynin was approved and widely used over for more than forty years, only one published case of suspected liver injury has been reported—a patient experienced a severe ischemic stroke several weeks after starting oxybutynin, with transient elevations in serum enzymes but no jaundice or other obvious symptoms. Therefore, clinically significant liver injury caused by oxybutynin, even if it occurs, is extremely rare. Probability score: E (unlikely to be the cause of clinically significant liver injury). Pregnancy and Lactation Effects ◉ Overview of Use During Lactation There is currently no information regarding the use of oxybutynin during lactation. Long-term use of oxybutynin may reduce milk production or the milk ejection reflex, but a single dose is unlikely to affect breastfeeding. During long-term use, signs of reduced milk production (e.g., dissatisfaction, poor weight gain) should be observed.
◉ Effects on Breastfed Infants
As of the revision date, no relevant published information was found.
◉ Effects on Lactation and Breast Milk
Anticholinergic drugs can inhibit lactation in animals, possibly by suppressing the secretion of growth hormone and oxytocin. Anticholinergic drugs can also lower serum prolactin levels in non-lactating women. Prolactin levels in established lactating mothers may not affect their ability to breastfeed. Manufacturers have reported cases of lactation suppression in some hydroxybutyrine (immediate-release formulation) during postmarketing surveillance.

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Protein Binding
Hydroxybutyrine enantiomers bind to plasma proteins at a rate exceeding 97%, primarily to α1 acid glycoprotein.

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Toxicity Overview
If hydroxybutyrine overdose is suspected, seek immediate medical attention. Symptoms of hydroxybutyrine overdose may include central nervous system hyperexcitability, fever, arrhythmia, vomiting, respiratory failure, paralysis, and coma. Treatment for hydroxybutyrine overdose typically includes supportive care by healthcare professionals. In some cases, healthcare professionals may consider giving patients activated charcoal to help absorb excess medication in the digestive system. Alternatively, laxatives may be used to promote bowel movements and help eliminate the medication from the body. Two cases of overdose due to taking 100 mg of hydroxybutyrine have been reported: one involving a 13-year-old boy and the other a 34-year-old woman. There was also one case involving concurrent alcohol consumption. Another case involved a 4-year-old boy who overdosed on 17 mg of hydroxybutyrine within 12 hours and developed central anticholinergic syndrome. All patients in these cases fully recovered after receiving supportive care from healthcare professionals. Extended-release hydroxybutyrine formulations contain insoluble components, which may lead to the formation of bezoars (gastric stones).

[1]. The anticholinergic drug oxybutynin inhibits voltage-dependent K+ channels in coronary arterial smooth muscle cells. Clin Exp Pharmacol Physiol. 2019 Nov;46(11):1030-1036.

[2]. Comparative evaluation of central muscarinic receptor binding activity by oxybutynin, tolterodine and darifenacin used to treat overactive bladder. J Urol. 2007 Feb;177(2):766-70.

Oxybutynin is a racemic mixture composed of equimolar amounts of (R)-hydroxybutynin and (E)-hydroxybutynin. It is an antispasmodic drug used to treat overactive bladder (OAB). Oxybutynin has a variety of pharmacological effects, including muscarinic receptor antagonist, muscle relaxant, antispasmodic, parasympathetic blocker, calcium channel blocker, and local anesthetic. It is a tertiary amine compound belonging to the racemic mixture, containing (R)-hydroxybutynin and (E)-hydroxybutynin. Overactive bladder (OAB) is a common condition that negatively impacts the lives of millions of patients worldwide. Due to its urinary symptoms, including nocturia, urgency, and frequency, this condition can lead to social embarrassment and a decreased quality of life. Oxybutynin, also marketed under the brand name Ditropan XL, is an anticholinergic drug used to relieve symptoms of OAB. Since its initial FDA approval in 1975, the drug's safety and efficacy have been optimized. This medication can relieve unpleasant urinary symptoms and improve the quality of life for patients with overactive bladder (OAB). It is commonly used as a first-line treatment for OAB. Oxibutin is a cholinergic muscarinic receptor antagonist. Its mechanism of action is as a cholinergic muscarinic receptor antagonist. Oxibutin is a synthetic anticholinergic drug used to treat urinary incontinence and overactive bladder. Oxibutin does not cause elevated liver enzymes or clinically significant acute liver injury. Oxibutin is a tertiary amine with antimuscarinic and antispasmodic effects. Oxibutin reduces involuntary muscle contractions by blocking muscarinic receptors in smooth muscle, inhibiting the binding of acetylcholine. Oxibutin reduces bladder contractions by relaxing bladder smooth muscle. See also: Oxibutin hydrochloride (salt form).

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Drug Indications
Oxibutin is indicated for the treatment of urinary urgency, frequency, and other symptoms caused by overactive bladder.
Oxybutine can also be used to treat detrusor overactivity in children aged 6 years and older, a condition associated with neurological disorders. Spina bifida is one such neurological disorder, and oxybutine can be used to control its urinary symptoms. Oxybutine is sometimes used to relieve bladder spasms caused by ureteral stents or catheters (this is off-label use). It is also used to treat urge incontinence and/or urinary frequency and urgency symptoms that may occur in adult patients with bladder instability. Mechanism of Action: Oxybutine relaxes the bladder by inhibiting the muscarinic effects of acetylcholine on smooth muscle (rather than skeletal muscle). The active metabolite of oxybutine is N-deethylhydroxybutine. It competitively inhibits postganglionic muscarinic receptors type 1, 2, and 3. This action increases bladder capacity, thereby reducing urinary frequency and urgency symptoms. Furthermore, oxybutine can delay the onset of the first urge to urinate.
Bladder pressure studies showed that the drug increased bladder capacity at the first contraction and the first urge to urinate, as well as bladder capacity at the end of the bladder pressure test. /chloride/

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- Mechanism of action: Oxybutynin exerts its anticholinergic effect by competitively blocking muscarinic receptors (especially M3 receptors in the bladder), thereby reducing detrusor muscle contraction. Compared with tolterodine and dafinarax, its higher central muscarinic receptor occupancy may lead to central nervous system-related side effects. [2]
- Clinical application: Approved for the treatment of overactive bladder and relief of symptoms such as urinary frequency, urgency and incontinence. [2]

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Oxibutin is an anticholinergic drug primarily used to treat overactive bladder[2]
- Its pharmacological action is achieved through competitive antagonism of muscarinic acetylcholine receptors (especially the M3 subtype) and inhibition of voltage-dependent K+ channels in certain smooth muscle cells[1][2]
- Oxibutin has a higher affinity for central muscarinic receptors than tolterodine and dafinaraxine, which may be related to its central nervous system-related side effects[2]
- The inhibitory effect of oxybutin on Kv channels in coronary smooth muscle may lead to its potential cardiovascular effects[1]

C22H31NO3

357.49

357.23

C, 73.92; H, 8.74; N, 3.92; O, 13.43

5633-20-5

Oxybutynin;5633-20-5;Oxybutynin chloride;1508-65-2;(R)-Oxybutynin hydrochloride;1207344-05-5;Oxybutynin-d11 chloride;1185151-95-4; Oxybutynin;5633-20-5;(R)-Oxybutynin hydrochloride;1207344-05-5;Oxybutynin-d11 chloride;1185151-95-4;(R)-Oxybutynin;119618-21-2; 5633-20-5 (racemate); 1508-65-2 (racemate HCl); 1207344-05-5 (R-isomer HCl); 119618-21-2 (R-isomer); 2738613-22-2 (R-isomer citrate); 119618-22-3 (S-isomer); 2862851-81-6 (R-isomer tartrate); 230949-16-3 (S-isomer HCl)

4634

Typically exists as White to off-white solids at room temperature

1.1±0.1 g/cm3

494.4±45.0 °C at 760 mmHg

125 - 130ºC

252.8±28.7 °C

0.0±1.3 mmHg at 25°C

1.546

5.19

1

4

8

26

490

0

O([H])C(C(=O)OC([H])([H])C#CC([H])([H])N(C([H])([H])C([H])([H])[H])C([H])([H])C([H])([H])[H])(C1C([H])=C([H])C([H])=C([H])C=1[H])C1([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C1([H])[H]

XIQVNETUBQGFHX-UHFFFAOYSA-N

InChI=1S/C22H31NO3/c1-3-23(4-2)17-11-12-18-26-21(24)22(25,19-13-7-5-8-14-19)20-15-9-6-10-16-20/h5,7-8,13-14,20,25H,3-4,6,9-10,15-18H2,1-2H3

4-(diethylamino)but-2-ynyl 2-cyclohexyl-2-hydroxy-2-phenylacetate

Ditropan, Lyrinel XL, Lenditro,Oxybutynin, Ditropan; 5633-20-5; Oxibutinina; Cystrin; Oxytrol; Oxibutyninum; kentera; Oxybutynine; Oxybutyninum; Uripan

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)

Solubility in Formulation 1: 2.08 mg/mL (5.82 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 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: ≥ 2.08 mg/mL (5.82 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 20.8 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: ≥ 2.08 mg/mL (5.82 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 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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