<p>No interactions have been observed between Nizatidine&nbsp;and theophylline, chlordiazepoxide, lorazepam, lidocaine, phenytoin, and&nbsp;warfarin. Nizatidine&nbsp;does not inhibit the cytochrome P-450-linked drug-metabolizing enzyme system; therefore, drug interactions mediated by inhibition of hepatic&nbsp;metabolism&nbsp;are not expected to occur. In patients given very high doses (3,900 mg) of&nbsp;aspirin&nbsp;daily, increases in serum salicylate levels were seen when nizatidine, 150 mg&nbsp;b.i.d., was administered concurrently.</p>