Pharmacodynamic properties
Dembrexine reduces the viscosity of respiratory mucus by fragmenting the sputum fibre network, and increasing pulmonary surfactant and respiratory compliance.
Pharmacokinetic particulars
Absorption: Absorption of dembrexine from the gut in the horse is practically complete as evident from the large percentage excreted in the urine. Following oral administration of dembrexine the absolute bioavailability of unchanged drug is about 30% (see also the information under the subheading "Metabolism" below). Steady state concentrations of dembrexine in plasma are reached within 2 days after repeated twice daily oral administration. At that time mean maximum plasma concentrations of 0.15 ng dembrexine/ml are observed about 1 hour post dose.
Distribution: There is a linear relationship between the dose administered and the plasma concentration observed in the therapeutic dose range. The volume of distribution is approximately 5 l/kg.
Metabolism: The parent compound trans-dembrexine occurs in plasma, liver and kidneys. Due to a first pass isomerization the stereoisomer of trans-dembrexine, i.e. cis-dembrexine, can also be found. Further metabolites occur as conjugates of dembrexine and there is also some highly polar material. Both trans- and cis-dembrexine are pharmacologically active.
Elimination: Dembrexine is eliminated with a half life in the order of 8 hours. Approximately 85% of the administered dose is excreted via urine and the remainder via faeces.