Some Plasma Pharmacokinetic Parameters of Isoniazid in the Presence of a Fluoroquinolone Antibacterial Agent
The effects of ciprofloxacin (CP), a fluoroquinolone antibacterial agent, on the extent of absorption of isoniazid (INH) and on some of its pharmacokinetic parameters were investigated in six healthy female volunteers between the ages of 23 and 32 years. The presence of CP led to increase in the amount of INH and to a slight reduction in its peak plasma concentration (C max ). There was a 1-hour increase in the time to attain C max (t max ) of INH, indicating absorption interaction between the two drugs. This absorption interaction was related to inhibition of cholinergic neurotransmission caused by CP, which is capable of inhibiting gastric motility, leading to a delay in gastric emptying. The rate of elimination (K) and plasma half-life (t 1/2 ) of INH were not significantly affected (P = 0.05). The extent of absorption interaction that may have occurred (based on values of 24-hour values for area under the concentration curve, C max, T max, K, and t 1/2 ) was considered to be of no therapeutic consequence, and the coadministration of the two drugs may be recommended in clinical practice.