Pharmacodynamic properties
Like other belladonna alkaloid derivatives, this compound antagonises the actions of acetylcholine at the muscarinic receptor and also possesses slight additional activity at nicotinic receptors. Its pharmacological profile is qualitatively similar to the principal member of this class, atropine. In contrast to atropine hyoscine butylbromide does not cross the blood-brain barrier and exhibits less impact on the cardiovascular system as well as less inhibition of salivary and lacrimal secretion. In comparison to atropine the duration of effect is shorter and disappears without any antidote. The antispasmodic effect of hyoscine butylbromide results in relaxation of smooth musculature lasting for approximately 20 - 45 minutes. A dose dependent increase in heart rate as well as inhibition of salivation and lacrimation can be observed.
Pharmacokinetic particulars
The quaternary ammonium structure of the active substance prevents penetration into the central nervous system after parenteral administration. The elimination half-life from plasma in the target species is 1 - 2 hours. Hyoscine butylbromide is very rapidly eliminated from the blood. Two hours after the intravenous administration of the product, serum levels of hyoscine butylbromide fall below the lower limit of detection of 100 ng/ml. After parenteral administration in horses, hyoscine butylbromide is eliminated mainly via urine, mainly as unchanged substance.