Niferin SR Drug Interactions

Antihypertensive drugs: The blood pressure lowering effect of nifedipine may be potentiated upon co-administration of other antihypertensive drugs.
β-receptor blockers: When nifedipine is administered simultaneously with β-receptor blockers the patient should be carefully monitored, since fairly severe hypotension can occur. Deterioration of heart failure is also known to develop in isolated cases.
Cytochrome P450 3A4: Nifedipine is metabolized via the cytochrome P450 3A4 system, located both in the intestinal mucosa and in the liver. Drugs that are known to either inhibitor to induce this enzyme system may therefore alter the first pass (after oral administration) or the clearance of nifedipine.
Digoxin: The simultaneous administration of nifedipine and digoxin may lead to reduced digoxin clearance and hence an increase in plasma concentrations of digoxin. The patient should therefore be checked for symptoms of digoxin overdosage as a precaution and, if necessary, the glycoside dose should be reduced taking account of the plasma concentration of digoxin.
Quinidine: When nifedipine and quinidine have been administered simultaneously, lowered quinidine or after discontinuation of nifedipine, a distinct increase in plasma concentrations of quinidine have been observed in individual cases. For this reason, when nifedipine is either additionally administered or discontinued, monitoring of the quinidine plasma concentration and, if necessary, adjustment of the quinidine dose are recommended.
Some authors reported increased plasma concentrations of nifedipine upon co-administration of both drugs, while others did not observe an alteration in the pharmacokinetics of nifedipine. Therefore, the blood pressure should be carefully monitored, if quinidine is added to an existing therapy with nifedipine. If necessary, the dose of nifedipine should be decreased.
Cimetidine: Due to its inhibition of cytochrome P450 3A4, cimetidine elevates the plasma concentrations of nifedipine and may potentiate the antihypertensive effect.
Rifampicin: It strongly induces the cytochrome P450 3A4 system. Upon co-administration with rifampicin, the bioavailability of nifedipine is distinctly reduced and thus its efficacy weakened. The use of nifedipine in combination with rifampicin is therefore contraindicated.
Diltiazem: It decreases the clearance of nifedipine. The combination of both drugs should be administered with caution and a reduction of the nifedipine dose may be considered.
Grapefruit juice: It inhibits the cytochrome P450 3A4 system. Administration of nifedipine together with grapefruit juice thus results in elevated plasma concentrations of nifedipine due to an increase of drug bioavailability. As a consequence, the blood pressure lowering effect may be increased.
Theoretical Potential Interactions: Phenytoin: A formal interaction study investigating the potential of a drug interaction between nifedipine and phenytoin has not yet been performed. However, phenytoin is known as a potential inducer of the cytochrome P450 3A4 system. Furthermore, concomitant administration of phenytoin and drugs structurally related to nifedipine clearly reduced their bioavailability. Thus a clinically relevant reduction of the bioavailability of nifedipine cannot be excluded.
Erythromycin: No interaction studies have been carried out between nifedipine and erythromycin. Erythromycin is known to inhibit the cytochrome P450 3A4 mediated metabolism of other drugs. Therefore the potential for an increase of nifedipine plasma concentrations upon co-administration of both drugs cannot be excluded.
Ketoconazole, Itraconazole, Fluconazole: A formal interaction study investigating the potential of a drug interaction between nifedipine and ketoconazole, itraconazole or fluconazole has not yet been performed. Drugs of this class are known to inhibit the cytochrome P450 3A4 system. When administered orally together with nifedipine, a substantial increase in systemic bioavailability of nifedipine due to an increased absorption cannot be excluded. Upon co-administration, the blood pressure should be monitored and, if necessary, a reduction in the nifedipine dose considered.
Tacrolimus: It has been shown to be metabolized via the cytochrome P450 3A4 system. Data recently published indicate that the dose of nifedipine administered simultaneously with tacrolimus may be reduced in individual cases. Upon co-administration of both drugs, the blood pressure should be monitored and, if necessary, a reduction in the nifedipine dose considered.
Interactions Shown Not to Exist: Concomitant administration of nifedipine with Ajmaline, Benazepril, Debrisoquine, Doxazosin, Omeprazole, Orlistat, pantoprazole, Ranitidine has no effect on the pharmacokinetics of either substance.
Aspirin: Concomitant administration of nifedipine and aspirin 100 mg has no effect on the pharmacokinetics of nifedipine. Co-administration of nifedipine does not alter the effect of aspirin 100 mg on the platelet aggregation and bleeding time.
Other Forms of Interactions: Nifedipine may cause falsely increased spectrophotometric values of urinary vanillyl-mandelic acid. However, measure with HPLC is unaffected. Antagonists like nifedipine should be considered as possible causes.