Introduction
Dicyclomine is a muscarinic M1, M3, and M2 receptor antagonist as well as a non-competitive inhibitor of histamine and bradykinin used to treat spasms of the intestines seen in functional bowel disorder and irritable bowel syndrome. Though it is commonly prescribed, its recommendation may have been based on a small amount of evidence and so its prescription is becoming less favourable.
Uses
Dicyclomine is an antimuscarinic agent used to treat IBS.
Dicyclomine is indicated for the treatment of functional bowel disorder and irritable bowel syndrome.
Associated Conditions
Pharmacodynamics
Dicyclomine is an anticholinergic drug used to relax the smooth muscles of the intestines. It's duration of action is not especially long as it is usually taken 4 times daily with individual doses of 20-40mg orally or 10-20mg by intramuscular injection. Dicyclomine should not be administered intravenously.
Mechanism of Action
Dicyclomine achieves its action partially through direct antimuscarinic activity of the M1, M3, and M2 receptors; and partially through antagonism of bradykinin and histamine. Dicyclomine non-competitively inhibits the action of bradykinin and histamine, resulting in direct action on the smooth muscle, and decreased strength of contractions seen in spasms of the ileum.
Absorption
The bioavailability of dicyclomine has not been determined, though it is likely well absorbed as the primary route of elimination is in the urine. Dicyclomine has a Tmax of 1-1.5h.
Volume of Distribution
The volume of distribution for a 20mg oral dose is 3.65L/kg.
Protein Binding
Data regarding plasma protein binding of dicyclomine is not readily available.
Route of Elimination
Dicyclomine is 79.5% eliminated in the urine and 8.4% in the feces.
Half Life
The mean plasma elimination half life is approximately 1.8 hours.
Clearance
Data regarding the clearance of dicyclomine is not readily available.
Toxicity
Patients experiencing an overdose may present with headache, nausea, vomiting, blurred vision, dilated pupils, dizziness, dry mouth, difficulty swallowing, CNS stimulation, as well as hot, dry skin. Treat patients with gastric lavage, emetics, activated charcoal, sedatives for excitement, and a cholinergic agent if indicated.
The oral LD50 in mice is 625mg/kg.
Food Interactions
- Avoid alcohol. Alcohol may increase drowsiness caused by dicyclomine.
- Drink plenty of fluids. Dicyclomine may reduce sweating, increasing the risk of overheating in warm weather or during exercise.
Dosage
- Adults:10 to 20 mg three times a day.
- Children over 6 months of age: 5 to 10 mg three times a day.
- Adults: Intramuscular injection. Not for intravenous use. The recommended intramuscular dose is 80 mg daily (in 4 equally divided doses).
Children: Dose must be determined by the doctor.
