Drug Interaction Report
1 potential interaction and/or warning found for the following 2 drugs:
- fosphenytoin
- omeprazole
Interactions between your drugs
omeprazole fosphenytoin
Applies to: omeprazole, fosphenytoin
MONITOR: Omeprazole may increase phenytoin serum concentrations and the risk of toxicity. The proposed mechanism is decreased clearance due to omeprazole-mediated inhibition of CYP450 2C19. Omeprazole may interact in a similar manner with other hydantoins. The clinical significance is unknown; however, higher omeprazole doses (more than 40 mg/day) may be more likely to interact.
MANAGEMENT: Clinical and laboratory monitoring may be appropriate whenever omeprazole is added to or withdrawn from therapy with phenytoin. Dosage adjustments may be considered if an interaction is suspected. Patients should be advised to notify their doctor if they experience symptoms of phenytoin toxicity (e.g., drowsiness, visual disturbances, change in mental status, seizures, nausea, or ataxia).
References (6)
- Andersson T (1991) "Omeprazole drug interaction studies." Clin Pharmacokinet, 21, p. 195-212
- Gugler R, Jensen JC (1985) "Omeprazole inhibits oxidative drug metabolism: studies with diazepam and phenytoin in vivo and 7-ethoxycoumarin in vitro." Gastroenterology, 89, p. 1235-41
- Prichard PJ, Walt RP, Kitchingman GK, et al. (1987) "Oral phenytoin pharmacokinetics during omeprazole therapy." Br J Clin Pharmacol, 24, p. 543-5
- (2022) "Product Information. PriLOSEC (omeprazole)." Merck & Co., Inc
- Cerner Multum, Inc. "UK Summary of Product Characteristics."
- Cerner Multum, Inc. "Australian Product Information."
Drug and food interactions
No alcohol/food interactions were found with the drugs in your list. However, this does not necessarily mean no food interactions exist. Always consult your healthcare provider.
Therapeutic duplication warnings
No duplication warnings were found for your selected drugs.
Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.
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Drug Interaction Classification
| Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. | |
| Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. | |
| Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. | |
| No interaction information available. |
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