ATCvet code: QA03DB04

Hyoscine butylbromide (butylscopolamine bromide) is a quaternary ammonium compound of hyoscine and 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 antagonises the actions of acetylcholine mediated through the muscarinic receptor. It also has some antagonist effect at nicotinic receptors. Due to its chemical structures as a quaternary ammonium derivative, hyoscine is not expected to enter the central nervous system therefore, does not produce secondary anticholinergic effects in the central nervous system.

Metamizole belongs to the group of pyrazolone derivatives and is used as an analgesic, antipyretic and spasmolytic agent. It has significant central analgesic and antipyretic, but only low anti-inflammatory effect (weak analgesics). Metamizole inhibits the synthesis of prostaglandins by blocking the cyclooxygenase. The analgesic and antipyretic effect is mainly due to inhibition of prostaglandin E2 synthesis. In addition, metamizole has a spasmolytic effect on smooth muscle organs. Metamizole sodium further antagonises the effects of bradykinin and histamine.

Hyoscine butylbromide is 17–24% bound to plasma proteins. The elimination half-life is 2-3 hours. Hyoscine butylbromide is mainly eliminated unchanged in urine (approx. 54%).

Metamizole sodium is rapidly metabolised by hydrolysis into the primary pharmacologically active metabolite 4 methyl-aminoantipyrine (MAA). Other metabolites (4 acetyl aminoantipyrine (AAA), 4 formyl aminoantipyrine (FAA) and aminoantipyrine (AA)) are present in smaller quantities. Plasma protein binding of the metabolites is as follows: MAA: 56%, AA: 40%, FAA: 15%, AAA 14%. The elimination half-life of MAA is 6 hours. Metamizole is primarily eliminated renally.