Revision Year: 2017 Publisher: Medochemie Ltd, 1-10 Constantinoupoleos Street, 3011 Limassol, Cyprus
Pharmacotherapeutic group: Belladonna alkaloids, semisynthetic, quaternary ammonium compounds
ATC code: A03BB01
Hyoscine butylbromide is an antispasmodic agent which relaxes smooth muscle of the organs of the abdominal and pelvic cavities. It is believed to act predominantly on the intramural parasympathetic ganglia of these organs.
Hyoscine butylbromide, due to its chemical structure as a quaternary ammonium derivate, is not expected to enter the central nervous system. Hyoscine butylbromide does not readily pass the bloodbrain barrier. However, it cannot totally be ruled out that under certain circumstances psychiatric disorders (e.g. confusion) may also occur after administration of hyoscine butylbromide.
After intravenous administration hyoscine butylbromide is rapidly distributed (t½α=4 min, t½β=29 min) into the tissues. The volume of distribution (Vss) is 128 L (corresponding to approx.1.7 L/kg). Because of its high affinity for muscarinic receptors and nicotinic receptors, hyoscine butylbromide is mainly distributed on muscle cells of the abdominal and pelvic area as well as in the intramural ganglia of the abdominal organs. Plasma protein binding (albumin) of hyoscine butylbromide is approximately 4.4%. Animal studies demonstrate that hyoscine butylbromide does not pass the bloodbrain barrier, but no clinical data to this effect is available.
The main metabolic pathway is the hydrolytic cleavage of the ester bond. The half-life of the terminal elimination phase (t½γ) is approximately 5 hours. The total clearance is 1.2 L/min. Clinical studies with radiolabeled hyoscine butylbromide show that after intravenous injection 42 to 61% of the radioactive dose is excreted renally and 28.3 to 37% faecally. The portion of unchanged active ingredient excreted in the urine is approximately 50%. The metabolites excreted via the renal route bind poorly to the muscarinic receptors and are therefore not considered to contribute to the effect of the hyoscine butylbromide.
No particular pharmacokinetic studies concerning hyoscine butylbromide have been performed in children.
In limited reproductive toxicity studies hyoscine butylbromide showed no evidence of teratogenicity in rats at 200 mg/kg in the diet or in rabbits at 200 mg/kg by oral gavage or 50 mg/kg by subcutaneous injection. Fertility in the rat was not impaired at doses of up to 200 mg/kg in the diet.
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