Anticholinergic – Antispasmodic
Action And Clinical Pharmacology: Oxybutynin is a tertiary amine anticholinergic agent which exerts antimuscarinic as well as direct antispasmodic action on smooth muscle. In vitro studies have shown that its anticholinergic effects are weaker than those of atropine, but that it possesses greater antispasmodic activity. No blocking effects occur at skeletal neuromuscular junctions or in autonomic ganglia (e.g., no antinicotinic effects).
In addition to its smooth muscle relaxing effects, oxybutynin exerts an analgesic and a local anesthetic effect. In animal studies the CNS and cardiovascular actions of oxybutynin were shown to be similar to but weaker than those of atropine.
Oxybutynin relaxes bladder smooth muscle. In patients with uninhibited neurogenic and reflex neurogenic bladder, cystometric studies have demonstrated that oxybutynin increases bladder (vesical) capacity, diminishes the frequency of uninhibited contractions of the detrusor muscle, and delays the initial desire to void. Oxybutynin thus decreases urgency and the frequency of both incontinent episodes and voluntary urination. These effects are more consistently improved in patients with uninhibited neurogenic bladder.
Oxybutynin is readily absorbed from the gastrointestinal tract. The onset of action is approximately 1 hour after an oral dose and its duration 6 to 10 hours.
Indications And Clinical Uses: For the relief of symptoms associated with voiding in patients with uninhibited neurogenic and reflex neurogenic bladder (i.e., urgency, frequency, urinary leakage, urge incontinence, dysuria).
Contra-Indications: Glaucoma, partial or complete obstruction of the gastrointestinal tract, paralytic ileus, intestinal atony of the elderly or debilitated patient, megacolon, toxic megacolon complicating ulcerative colitis, severe colitis, myasthenia gravis, obstructive uropathy, and when the patient has an unstable cardiovascular status in acute hemorrhage. Hypersensitivity to oxybutynin.
Manufacturers’ Warnings In Clinical States: When oxybutynin is administered in the presence of high environmental temperature, it can cause heat prostration (fever and heat stroke due to decreased sweating).
Diarrhea may be an early symptom of incomplete intestinal obstruction, especially in patients with ileostomy or colostomy. In such cases, treatment with oxybutynin would be inappropriate and possibly harmful.
Occupational Hazards: Oxybutynin may produce drowsiness or blurred vision. The patient should be cautioned regarding activities requiring mental alertness, such as operating a motor vehicle or other machinery or performing hazardous work while taking this drug. Alcohol or other sedative drugs may enhance the drowsiness caused by oxybutynin.
Pretreatment examinations should include cystometry and other appropriate diagnostic procedures. Cystometry should be repeated at appropriate intervals to evaluate response to therapy. The appropriate antimicrobial therapy should be instituted in the presence of infection.
Precautions: Oxybutynin should be used with caution in the elderly and in patients with autonomic neuropathy, hepatic or renal disease. Administration of oxybutynin in large doses to patients with ulcerative colitis may suppress intestinal motility to the point of producing a paralytic ileus and precipitate or aggravate toxic megacolon, a serious complication of the disease.
The symptoms of hyperthyroidism, coronary heart disease, congestive heart failure, cardiac arrhythmias, tachycardia, hypertension and prostatic hypertrophy may be aggravated following administration of oxybutynin. The drug should be administered with caution to patients with hiatal hernia associated with reflux esophagitis, since anticholinergic drugs may aggravate this condition.
Pregnancy: The safety of oxybutynin in pregnancy has not been established. Therefore, oxybutynin should not be used in women of childbearing potential, unless, in the opinion of the physician, the expected benefit to the patient outweighs the possible risk to the fetus.
Lactation: It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when oxybutynin is administered to a nursing woman.
Children: Because the safety of oxybutynin in children under the age of 5 has not been established, use of the drug in this age group is not recommended.
Adverse Reactions: Dry mouth and throat, difficulty swallowing, decreased sweating, urinary hesitance and retention, blurred vision, dilation of the pupil, cycloplegia, increased ocular tension, palpitations, tachycardia, chest pain, syncope, flushing, nose bleed, drowsiness, weakness, dizziness, headache, insomnia, mood changes, nausea, vomiting, anorexia, metallic taste, constipation, bloated feeling, edema, impotence, suppression of lactation, interference with normal heat regulation, severe allergic reactions or drug idiosyncrasies including urticaria and other dermal manifestations.
Symptoms And Treatment Of Overdose: Symptoms: The symptoms of overdosage with oxybutynin may be any of those seen with other anticholinergic agents. Symptoms may include signs of CNS excitation (e.g., restlessness, tremor, irritability, delirium, hallucinations), flushing, fever, nausea, vomiting, tachycardia, hypotension or hypertension, respiratory failure, paralysis and coma.
Treatment: In the event of an overdose or exaggerated response, treatment should be symptomatic and supportive. Induce emesis or perform gastric lavage (emesis is contraindicated in precomatose, convulsive, or psychotic state) and maintain respiration. Activated charcoal may be administered as well as magnesium sulfate. Physostigmine may be considered to reverse symptoms of anticholinergic intoxication. Hyperpyrexia may be treated symptomatically with ice bags or other cold applications and alcohol sponges.
Dosage And Administration: Adults: 5 mg 2 to 3 times a day. Maximum recommended dose: 5 mg 4 times a day.
In elderly and debilitated patients it is advisable to initiate treatment at the lowest recommended dosage and to increase the dosage carefully according to tolerance and response.
Children over 5 years of age: 5 mg 2 times a day. Maximum recommended dose: 5 mg 3 times a day.
Availability And Storage: Tablets: Each scored, biconvex, blue tablet, engraved with Ditropan on one side and 1375 on the other side contains: oxybutynin chloride 5 mg. Nonmedicinal ingredients: calcium stearate, FD&C Blue #1 lake, lactose and microcrystalline cellulose. Bottles of 100 and 500. Store at controlled room temperature of 15 to 30°C in tight, light resistant containers.
Syrup: Each 5 mL of green colored syrup contains: oxybutynin chloride 5 mg. Nonmedicinal ingredients: citric acid, FD&C Green #3, flavor, glycerin, methylparaben, sodium citrate, sorbitol, sucrose and water. Bottles of 473 mL. Store at controlled room temperature of 15 to 30°C.
DITROPAN® Alza Canada Oxybutynin Chloride Anticholinergic – Antispasmodic