Bentyl - Pharmaceutical Information, Clinical Trials, Detailed Pharmacology, Toxicology
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Bentyl - Scientific Information

Manufacture: Forest Laboratories, Inc.
Country: United States
Condition: Irritable Bowel Syndrome
Class: Anticholinergics/antispasmodics
Form: Liquid solution, Intramuscular (IM), Tablets, Capsules
Ingredients: dicyclomine hydrochloride, calcium sulfate, corn starch, FD&C Blue No. 1, FD&C Red No. 40, gelatin, lactose, magnesium stearate, pregelatinized corn starch, and titanium dioxide; acacia, dibasic calcium phosphate, corn starch, FD&C Blue No. 1, lactose, magnesium stearate, pregelatinized corn starch, and sucrose; sterile water for injection, made isotonic with sodium chloride

Description

BENTYL is an antispasmodic and anticholinergic (antimuscarinic) agent available in the following dosage forms:

  • BENTYL capsules for oral use contain 10 mg dicyclomine hydrochloride USP. BENTYL 10 mg capsules also contain inactive ingredients: calcium sulfate, corn starch, FD&C Blue No. 1, FD&C Red No. 40, gelatin, lactose, magnesium stearate, pregelatinized corn starch, and titanium dioxide.
  • BENTYL tablets for oral use contain 20 mg dicyclomine hydrochloride USP. BENTYL 20 mg tablets also contain inactive ingredients: acacia, dibasic calcium phosphate, corn starch, FD&C Blue No. 1, lactose, magnesium stearate, pregelatinized corn starch, and sucrose.
  • BENTYL injection is a sterile, pyrogen-free, aqueous solution for intramuscular injection (NOT FOR INTRAVENOUS USE) supplied as an ampoule containing 20 mg/2 mL (10 mg/mL). Each mL contains 10 mg dicyclomine hydrochloride USP in sterile water for injection, made isotonic with sodium chloride.

    BENTYL (dicyclomine hydrochloride) is [bicyclohexyl]-1-carboxylic acid, 2-(diethylamino) ethyl ester, hydrochloride, with a molecular formula of C19H35NO2•HCl and the following structural formula:


Molecular weight: 345.95

Dicyclomine hydrochloride occurs as a fine, white, crystalline, practically odorless powder with a bitter taste. It is soluble in water, freely soluble in alcohol and chloroform, and very slightly soluble in ether.

Clinical Pharmacology

Mechanism of Action

Dicyclomine relieves smooth muscle spasm of the gastrointestinal tract. Animal studies indicate that this action is achieved via a dual mechanism:

  • a specific anticholinergic effect (antimuscarinic) at the acetylcholine-receptor sites with approximately 1/8 the milligram potency of atropine (in vitro, guinea pig ileum); and
  • a direct effect upon smooth muscle (musculotropic) as evidenced by dicyclomine's antagonism of bradykinin- and histamine-induced spasms of the isolated guinea pig ileum. 

Atropine did not affect responses to these two agonists. In vivo studies in cats and dogs showed dicyclomine to be equally potent against acetylcholine (ACh)- or barium chloride (BaCl2)-induced intestinal spasm while atropine was at least 200 times more potent against effects of ACh than BaCl2. Tests for mydriatic effects in mice showed that dicyclomine was approximately 1/500 as potent as atropine; antisialagogue tests in rabbits showed dicyclomine to be 1/300 as potent as atropine.

Pharmacodynamics

BENTYL can inhibit the secretion of saliva and sweat, decrease gastrointestinal secretions and motility, cause drowsiness, dilate the pupils, increase heart rate, and depress motor function.

Pharmacokinetics

Absorption and Distribution

In man, dicyclomine is rapidly absorbed after oral administration, reaching peak values within 60-90 minutes. Mean volume of distribution for a 20 mg oral dose is approximately 3.65 L/kg suggesting exentsive distribution in tissues.

Elimination

The metabolism of dicyclomine was not studied. The principal route of excretion is via the urine (79.5% of the dose). Excretion also occurs in the feces, but to a lesser extent (8.4%). Mean half-life of plasma elimination in one study was determined to be approximately 1.8 hours when plasma concentrations were measured for 9 hours after a single dose. In subsequent studies, plasma concentrations were followed for up to 24 hours after a single dose, showing a secondary phase of elimination with a somewhat longer half-life. 

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term animal studies have not been conducted to evaluate the carcinogenic potential of dicyclomine. In studies in rats at doses of up to 100 mg/kg/day, dicyclomine produced no deleterious effects on breeding, conception, or parturition. 

Clinical Studies

In controlled clinical trials involving over 100 patients who received drug, 82% of patients treated for functional bowel/irritable bowel syndrome with dicyclomine hydrochloride at initial doses of 160 mg daily (40 mg four times daily) demonstrated a favorable clinical response compared with 55% treated with placebo (p<0.05).