Pharmacodynamic properties
Butylscopolamine bromide is a spasmolytic agent with particular activity on the smooth muscle of the digestive and urinary systems. It antagonises the actions of acetylcholine at the muscarinic receptor and also has some activity at nicotinic receptors. Its pharmacological profile is similar to atropine, the main member of this class.
Pharmacokinetic properties
The quarternary ammonium structure confers poor absorption after oral administration and prevents penetration of the central nervous system after parenteral administration. 17-24% is plasma protein bound and plasma elimination half-life is 2-3 hours. It is excreted mostly unchanged - about 54% via the kidneys in urine after parenteral administration. After oral administration, only around 1% is excreted in urine.
Metamizole is a non-steroidal anti-inflammatory drug of the pyrazolone group and also has analgesic and anti-pyretic effects. It is rapidly absorbed with absolute bioavailability of nearly 100%. The primary metabolite in plasma and urine is 4-methyl-aminoantipyrine (MAA), which is pharmacologically active with a plasma half life of around 6 hours. Other metabolites are present in smaller quantities. The metabolites are bound (to various degrees) to plasma proteins, with 56% MAA bound. Excretion occurs mainly via the kidney, with 50-70% of the dose eliminated in urine, depending on species.