Antibacterial drugs, such as isoniazid can interact with other drugs in a wide variety of clinically significant ways. It is frequently administered with other prescription medications. The antibacterial agents may be affected by the action of another co-administered drug. Interactions involving antimicrobials often result from alterations in the hepatic metabolism or renal elimination of the drugs concurrently administered. Nonsteroidal anti-inflammatory drugs (NSAIDS) are the most widely used drugs. Drug interactions with this class of compounds are frequently reported and can be pharmacokinetics and/or pharmacodynamic in nature. Isoniazid and naproxen are co-administered in patients suffering from tuberculosis as well as osteoarthritis (mostly in developing countries). The aim of this investigation was to assess the effect of naproxen (500 mg) on the pharmacokinetics characteristics of isoniazid (300 mg) in ten healthy human volunteers in a complete cross-over design using high performance liquid chromatography (HPLC) method to analyze serum drug concentrations. Naproxen caused a highly significant (p<0.001) increase in AUC, significant (p<0.05) increase in elimination half life (t 1/2) and time for the maximum drug concentration (tmax) while significant (p<0.05) decrease in elimination rate constant (Ke). Insignificant decrease and increase was observed in absorption rate constant (Ka) and maximum drug concentration (Cmax), respectively. These results signify that naproxen enhances the concentration of isoniazid in serum therefore there is no harm to use them concurrently.
Muhammad Tayyab Ansari , Bashir Ahmed Loothar and Qasim Jahangir Khan , 2003. Effect of Concurrent Naproxen Administration on Pharmacokinetics of Isoniazid. Pakistan Journal of Biological Sciences, 6: 1849-1852.