Drug Interactions between fosphenytoin and Isoptin IV
This report displays the potential drug interactions for the following 2 drugs:
- fosphenytoin
- Isoptin IV (verapamil)
Interactions between your drugs
verapamil fosphenytoin
Applies to: Isoptin IV (verapamil) and fosphenytoin
Consumer information for this interaction is not currently available.
GENERALLY AVOID: Potent inducers of CYP450 3A4 may significantly decrease the plasma concentrations of most calcium channel blockers (CCBs), as CYP450 3A4 is the primary isoenzyme responsible for their metabolism. Some drug interaction studies have reported a significant reduction in plasma levels for certain CCBs. For example, when a single dose of nimodipine (60 mg) was administered to patients with epilepsy (n=8) who were also receiving chronic treatment with a potent CYP450 3A4-inducing antiepileptic agent (phenytoin, phenobarbital and/or carbamazepine), the mean areas under the plasma nimodipine concentration curve (AUC) were lowered by about 7-fold compared to the control group. In another drug interaction study comparing nisoldipine pharmacokinetics in epileptic patients on concurrent phenytoin therapy (n=12) to healthy controls (n=12), the AUC of nisoldipine was approximately 90% lower (1.6 vs 15.2 mcg/L/h) in patients on concomitant phenytoin therapy. Clinical data for all calcium channel blockers with potent CYP450 3A4 inducers are not available.
MANAGEMENT: Concomitant use of calcium channel blockers (CCBs) primarily metabolized by CYP450 3A4 with potent CYP450 3A4 inducers should generally be avoided. Additional monitoring and dose adjustments may be required if coadministration is necessary, particularly during initiation, titration, or discontinuation of the CYP450 3A4 inducer. Individual product labeling for the CCB should be consulted for further guidance.
Drug and food interactions
verapamil food
Applies to: Isoptin IV (verapamil)
You may take verapamil with or without food, but take it the same way every time. You should avoid consuming grapefruit or grapefruit juice as much as possible during treatment with verapamil. If you have been regularly consuming grapefruit or grapefruit juice with verapamil, do not increase or decrease the amounts of these products in your diet without first talking to your doctor. Grapefruit juice can increase the blood levels and effects of verapamil. Contact your doctor if you experience sudden, unexplained weight gain; swelling of the hands, ankles, or feet; chest pain; or difficulty breathing. Avoid driving or operating hazardous machinery until you know how the medication affects you, and use caution when getting up from a sitting or lying position. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
verapamil food
Applies to: Isoptin IV (verapamil)
Ask your doctor before using verapamil together with ethanol. Verapamil may increase the blood levels and intoxicating effects of ethanol. This can cause symptoms of extreme drowsiness, confusion, and nausea. If you experience any of these side effect you should avoid activities requiring mental alertness. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
verapamil food
Applies to: Isoptin IV (verapamil)
Using verapamil together with multivitamin with minerals can decrease the effects of verapamil. Talk with your doctor before using verapamil and multivitamin with minerals together. You may need a dose adjustment or need your blood pressure checked more often if you take both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
Therapeutic duplication warnings
No 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.
See also
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. |
Further information
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
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