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Drug Interactions between Cardizem LA and fosphenytoin

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Major

dilTIAZem fosphenytoin

Applies to: Cardizem LA (diltiazem) 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.

References

  1. Tada Y, Tsuda Y, Otsuka T, et al. (1992) "Case report: nifedipine-rifampicin interaction attenuates the effect on blood pressure in a patient with essential hypertension." Am J Med Sci, 303, p. 25-7
  2. (2001) "Product Information. Mycobutin (rifabutin)." Pharmacia and Upjohn
  3. (2001) "Product Information. Rifadin (rifampin)." Hoechst Marion Roussel
  4. Michelucci R, Cipolla G, Passarelli D, Gatti G, et al. (2024) Reduced plasma nisoldipine concentrations in phenytoin-treated patients with epilepsy https://pubmed.ncbi.nlm.nih.gov/8917062/
  5. Tartara A, Galimberti CA, Manni R, zucca c, et al. (2024) Differential effects of valproic acid and enzyme-inducing anticonvulsants on nimodipine pharmacokinetics in epileptic patients https://pubmed.ncbi.nlm.nih.gov/1777370/
View all 5 references

Drug and food interactions

Moderate

dilTIAZem food

Applies to: Cardizem LA (diltiazem)

Alcohol can lower your blood pressure and add to the effects of dilTIAZem. You may experience dizziness, lightheadedness, fainting, or a rapid heartbeat if you drink alcohol with dilTIAZem, especially when you first start taking the medication or just after a dose increase. Grapefruit juice may also increase the effects of dilTIAZem in some people by increasing its levels in the blood. You may want to limit alcohol intake and avoid excessive consumption of grapefruit and grapefruit juice during treatment with dilTIAZem. However, if you have been regularly consuming grapefruit or grapefruit juice with dilTIAZem, do not alter the amounts of these products in your diet without first talking to your doctor or other healthcare professional. Contact your doctor if your condition changes or you experience increased side effects of dilTIAZem such as headache, irregular heartbeat, swelling, unexplained weight gain, or chest pain. Orange juice is not expected to interact.

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Moderate

dilTIAZem food

Applies to: Cardizem LA (diltiazem)

Using dilTIAZem together with multivitamin with minerals can decrease the effects of dilTIAZem. Talk with your doctor before using dilTIAZem 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.

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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.


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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor 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.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.