Lansoprazole Phenytoin

While generally not of major concern, omeprazole may inhibit the metabolism of warfarin, diazepam, and phenytoin lansoprazole may decrease theophylline concentrations. Drug interactions with omeprazole are of particular concern in patients who are considered slow metabolizers, as are approximately 3% of the Caucasian population. Unfortunately, it is unclear which patients have the polymorphic gene variation that makes them slow metabolizers.17 The metabolism of esomeprazole may also be altered in patients with this polymorphic gene variation. Patients on potentially interacting drugs should be monitored for development of drug-related problems. 

Deravirdine (Rescnptor) [Antiretroviral/NNRTI] Uses HIV Infxn Action Nonnucleoside RT inhibitor Dose 400 mg PO tid Caution [C, ] CDC recommends HIV-infected mothers not to breast-feed (transmission risk) w/ renal/hepatic impair Contra Use w/ drugs dependent on CYP3A for clearance (Table VI-8) Disp Tabs SE Fat redistribution, immune reconstitution synd, HA, fatigue, rash, T transaminases, N/V/D Interactions T Effects W/ fluoxetine T effects OF benzodiazepines, cisapride, clarithromycin, dapsone, ergotamine, indinavir, lovastatin, midazolam, nifedipine, quinidine, ritonavir, simvastatin, terfena-dine, triazolam, warfarin effects W/ antacids, barbiturates, carbamazepine, cimetidine, famotidine, lansoprazole, nizatidine, phenobarbital, phenytoin, ranitidine, rifabutin, rifampin effects OF didanosine EMS Use of benzodiazepines and CCBs should be avoided may cause a widespread rash located on upper body and arms OD May cause an extension of nl SEs symptomatic and supportive Deferasirox (Exjade) [Iron Chelator] Uses Chronic iron overload d/t transfusion in pts >2 y Action Oral iron chelator Dose Initial 20 mg/kg... 

Substrates CYP2C19 Diazepam, lansoprazole, omeprazole, phenytoin. 

Clinically important, potentially hazardous interactions with aluminum, aminophylline, aspirin, chlorambucil, cimetidine, clarithromycin, cyclophosphamide, cyclosporine, dicumarol, diuretics, docetaxel, estrogens, grapefruit juice, indomethacin, influenza vaccines, itraconazole, ketoconazole, lansoprazole, live vaccines, methotrexate, montelukast, omeprazole, oral contraceptives, pancuronium, phenobarbital, phenytoin, ranitidine, rifampicin, rifampin, timolol, tolbutamide, vitamin A... 

Clinically important, potentially hazardous interactions with ciprofloxacin, clorazepate, ketoconazole, lansoprazole, lomefloxacin, phenytoin, sparfloxacin, tetracycline... 

Proton pnmp inhibitors Omeprazole Lansoprazole Pantoprazole Antiepileptics Diazepam Phenytoin Phenobarbitone Amitriptyline Clomipramine Cyclophosphamide Progesterone... 

Transporter efflux transporter effects predominant Examples Amiodarone Atorvastatin Azithromycin Carbamazepine Carvediioi Chlorpromazine Ciprofloxacin Cisapride Cyciosporine Danazoi Dapsone Diclofenac Diflunisal Digoxin Erythromycin Flurbiprofen Glipizide Glyburide Griseofulvin Ibuprofen Indinavir Indomethacin Itraconazole Ketoconazole Lansoprazole Lovastatin Mebendazole Naproxen Nelfinavir Ofloxacin Oxaprozin Phenazopyridine Phenytoin Piroxicam Raloxifene Ritonavir Saquinavir Saquinavir Sirolimus Sirolimus Spironolactone Spironolactone Tacrolimus Tacrolimus ... 

A study in epileptic patients found that omeprazole 20 mg daily did not affect the serum levels of phenytoin, whereas earlier studies in healthy subjects su ested that phenytoin levels might be modestly raised by omeprazole 40 mg daily. A study with esome-prazole also suggests it may cause a minor rise in phenytoin levels. Lansoprazole does not normally affect phenytoin levels, but an isolated case report of toxicity is tentatively attributed to an interaction. Pantoprazole and rabeprazole appear not to interact. 

Not understood. A possible explanation is that if the dosage of omeprazole is high enough, it may possibly reduce the metabolism of phenytoin by CYP2C19. However, CYP2C19 has only a minor role in phenytoin metabolism. Esomeprazole may interact similarly. With lansoprazole, the overall picture is that it does not act as an enzyme inducer or inhibitor ... 

Information is very limited but it seems that omeprazole 20 mg daily does not affect serum phenytoin levels, whereas 40 mg daily may possibly cause a slight increase. No special precautions would normally seem necessary if lansoprazole or omeprazole is given with phenytoin, but until more is known it would be prudent to be aware of this possible interaction if concurrent use is necessary. Similarly, the manufacturers of esomepra-zole suggest concurrent use should be monitored, although the elevation in levels seen in the study would not usually be expected to be clinically significant. More study is needed. No special precautions would seem to be necessary if rabeprazole or pantoprazole and phenytoin are given concurrently. 

Karol MD, Mukherji D, Cavanaugh JH. Lack of effect of concomitant multi-dose lansoprazole on single-dose phenytoin pharmacokinetics in subjects, Gastroenterology (1994) 106, A103. 

Karol MD, Locke CS, Cavanai h JH. Lack of a pharmacokinetic interaction between lansoprazole and intravenously administered phenytoin. JC/mP/jarwaco/ (1999) 39, 1283-9. 

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