Pharmacokinetics of benzydamine.

Clinically, benzydamine can exert its action locally or systemically. Consequently the pharmacokinetics of this drug have been studied after its administration by several different routes. Oral doses of benzydamine are apparently well absorbed and plasma drug concentrations reach a peak fairly rapidly (e.g. 0.8 micrograms/ml after a 100-mg dose) and then decline with a half-life of about 13 h. Less than 20% of the drug is bound to plasma proteins. Assuming complete oral systemic availability, values of 193 ml/min and 213 litres respectively were calculated for the systemic clearance and volume of distribution of benzydamine. Cutaneous doses of benzydamine are more slowly absorbed and lead to peak drug levels about three-fold lower, but more persistent than those after oral administration. Although local drug concentrations are relatively large, the systemic absorption of mouthwash-gargle, vaginal and rectal doses of benzydamine is relatively low compared to oral doses: this lower absorption should greatly diminish the potential for any systemic drug side-effects when benzydamine is administered by these routes. Benzydamine is metabolized primarily by oxidation, conjugation and dealkylation.