Gabapentin interaction with other drugs

Carbamazepine, phenytoin, pheno-barbital, and other anticonvulsants (except for gabapentin) induce hepatic enzymes responsible for drug biotransformation. Combinations between anticonvulsants or with other drugs may result in clinically important interactions (plasma level monitoring ). 

It is not necessary to monitor gabapentin plasma concentrations to optimize therapy. Further, because there are no significant pharmacokinetic interactions with other commonly used anti-epileptic drugs, the addition of gabapentin does not alter the plasma levels of these drugs appreciably. 

Gabapentin is absorbed after oral administration and is not metabolized in humans. It is not bound to plasma proteins. It is excreted unchanged, mainly in the urine. Its half-life, when it is used as monotherapy, is 4 to 6 hours. It has no known interactions with other antiseizure drugs. 

Gabapentin presents with minimal drug interaction so it appears versatile in combination with other neuropathic pain medications in clinical use. 

Drug/Lab test interactions Because false-positive readings were reported with the Ames N-Muitistix SG dipstick test for urinary protein when gabapentin was added to other antiepileptic drugs, the more specific sulfosalicylic acid precipitation procedure is recommended to determine the presence of urine protein. 

Drug interactions are infrequent with gabapentin. It does not induce hepatic metabolizing enzymes, nor do other AEDs affect its metabolism and elimination. Antacids may decrease absorption. Gabapentin dosage may need to be decreased in patients with renal disease or in the elderly. 

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