Gabapentin drug interactions

Gabapentin andpregabalin have very few if any significant drug interactions. 

Drug Interactions. Felbamate inhibits the clearance and increases the serum concentration of phenytoin, valproic acid, and phenobar-bital. The concentration of carbamazepine decreases in patients on concmrent therapy with felbamate secondary to enzyme induction however, the concentration of the 10,11 -epoxide metabolite increases. It is recommended that the dose of phenytoin, carbamazepine, and valproic acid be decreased by about 30% when felbamate is added. Felbamate does not appear to interact with either gabapentin or 1am-otrigine. Phenytoin and carbamazepine are enzyme inducers and have been shown to increase the clearance of felbamate. Interactions with warfarin also have been reported. ... 

B Advantages. Gabapentin has multiple mechanisms of action and is mechanistically different from first-generation AEDs. It is not metabolized and is excreted unchanged by the kidney. Gabapentin has the additional advantages of a broad therapeutic index with minimal CNS adverse effects and no drug interactions. Doses can be escalated rapidly. 

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. 

Pregabalin is another second-generation anticonvulsant that has recently obtained FDA approval for treatment of neurogenic pain, and several randomized placebo controlled studies have shown that this compound is efficacious in the treatment of painful diabetic neuropathy [32]. Doses between 300 and 600 mg/day have shown effect already apparent after 1 week of treatment. There are few clinically important drug interactions as there is no interference with the cytochrome 450 system. This compound requires minimal dose titration and seems easy to use. Side effects to gabapentin and pregabalin include drowsiness, dizziness and peripheral edema. 

Busch JA, Bockbrader HN, Randinitis EJ, Chang T, Welling PG, Reece PA Underwood B, Sedman AJ, Vollmer KO, Turck D. Lack of clinically significant drug interactions with Neurontin (Gabapentin). 20 International Epilepsy Congress. Oslo, Norway, July 1993. Abstract 013958. 

Anhut H, Leppik I, Schmidt B, Thomann P. Drug interaction study of the new anticonvulsant gabapentin with phen3rtoin in epileptic patients. Naunyn Schmiedebergs Arch Pharmacol (1988) 337 (Suppl), R127. 

Lai R, Sukbuntherng J, Luo W, Vicente V, Blumenthal R, Ho J, Cundy KC. Clinical pharmacokinetic drug interaction studies of gabapentin enacarbil, a novel transported prodrug of gabapentin, with naproxen and cimetidine. Br J Clin Pharmacol 2010 69(5) 498-507. 

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

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. 

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. 

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. 

---