Pharmacotherapeutic Group: Synthetic anticholinergics, esters with tertiary amino group. ATC Code: A03AA04.
Pharmacology: Pharmacodynamics: Mechanism of Action and Pharmacodynamic Effects: Colospasmin is a musculotropic antispasmodic with a direct effect on the smooth muscle of the gastrointestinal tract, relieving spasm without affecting normal gut motility. Since this effect is not mediated by the autonomic nervous system, the typical anticholinergic side effects are absent.
Pharmacokinetics: Absorption: Colospasmin is rapidly and completely absorbed after oral administration. The modified-release formulation permits a twice-daily dosing scheme.
Distribution: No significant accumulation occurs after multiple doses.
Biotransformation: Colospasmin is mainly metabolized by esterases, which split the ester bonds into veratric acid and Colospasmin alcohol firstly.
In plasma, demethylated carboxylic acid (DMAC) is the main metabolite. The steady-state elimination half-life t½ of DMAC is approximately 5.77 hrs. During multiple dosing (200 mg twice daily) the maximum plasma concentration (Cmax) of DMAC is 804 ng/mL and time to maximum plasma concentration (tmax) is about 3 hrs. The relative bioavailability appears to be optimal with a mean ratio of 97%.
Elimination: Colospasmin is not excreted as such, but metabolized completely; the metabolites are excreted nearly completely. Veratric acid is excreted into the urine, Colospasmin alcohol is also excreted into the urine, partly as the corresponding carboxylic acid (MAC) and partly as DMAC.
Paediatric Population: No pharmacokinetic studies have been conducted in children with any formulation of Colospasmin.
The primary mechanism of action of hexachlorophene, based on studies with Bacillus megatherium, is to inhibit the membrane-bound part of the electron transport chain, respiratory D-lactate dehydrogenase. It induces leakage, causes protoplast lysis, and inhibits respiration.
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Information checked by Dr. Sachin Kumar, MD Pharmacology