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Drugs that affect nifedipine: NICARDIA-XL-30 is metabolised via the cytochrome P450 3A4 system, located both in the intestinal mucosa and in the liver. Drugs that are known to either inhibit or to induce this enzyme system may therefore alter the first pass (after oral administration) or the clearance of NICARDIA-XL-30.
The extent as well as the duration of interactions should be taken into account when administering NICARDIA-XL-30 together with the following drugs: Rifampicin: Rifampicin strongly induces the cytochrome P450 3A4 system. Upon co- administration with rifampicin, the bioavailability of NICARDIA-XL-30 is distinctly reduced and thus its efficacy weakened. The use of NICARDIA-XL-30 in combination with rifampicin is therefore contraindicated.
Upon co-administration of known inhibitors of the cytochrome P450 3A4 system, the blood pressure should be monitored and, if necessary, a reduction in the NICARDIA-XL-30 dose considered. Drugs increasing NICARDIA-XL-30 exposure: Macrolide antibiotics (e.g., erythromycin); Anti-HIV protease inhibitors (e.g., ritonavir); Azole anti-mycotics (e.g., ketoconazole); Fluoxetine; nefazodone; quinupristin/dalfopristin; cisapride; valproic acid; Cimetidine; Diltiazem.
Upon co-administration of inducers of the cytochrome P450 3A4 system, the clinical response to NICARDIA-XL-30 should be monitored and, if necessary, an increase in the NICARDIA- XL-30 dose considered. If the dose of NICARDIA-XL-30 is increased during co-administration of both drugs, a reduction of the NICARDIA-XL-30 dose should be considered when the treatment is discontinued.
Drugs decreasing nifedipine exposure: rifampicin, phenytoin, carbamazepine, phenobarbital.
Effects of nifedipine on other drugs: NICARDIA-XL-30 may increase the blood pressure lowering effect of concomitant applied antihypertensives.
When NICARDIA-XL-30 is administered simultaneously with β-receptor blockers the patient should be carefully monitored, since deterioration of heart failure is also known to develop in isolated cases.
Digoxin: The simultaneous administration of NICARDIA-XL-30 and digoxin may lead to reduced digoxin clearance and, hence, an increase in the plasma digoxin level. The patient should therefore be subjected to precautionary checks for symptoms of digoxin overdosage and, if necessary, the glycoside dose should be reduced.
Quinidine: Co-administration of NICARDIA-XL-30 with quinidine may lower plasma quinidine levels, and after discontinuation of NCARDIA-XL-30, a distinct increase in plasma quinidine levels may be observed in individual cases. Consequently, when NICARDIA-XL-30 is either additionally administered or discontinued, monitoring of the quinidine plasma concentration, and if necessary, adjustment of the quinidine dose is recommended. Blood pressure should be carefully monitored and, if necessary, the dose of nifedipine should be decreased.
Tacrolimus: Tacrolimus is metabolised via the cytochrome P450 3A4 system. Published data indicate that the dose of tacrolimus administered simultaneously with NICARDIA-XL-30 may be reduced in individual cases. Upon co-administration of both drugs, the tacrolimus plasma concentrations should be monitored and, if necessary, a reduction in the tacrolimus dose considered.
Drug food interactions: Grapefruit juice inhibits the cytochrome P450 3A4 system. Administration of NICARDIA-XL- 30 together with grapefruit juice thus results in elevated plasma concentrations and prolonged action of nifedipine due to a decreased first pass metabolism or reduced clearance. As a consequence, the blood pressure lowering effect of NICARDIA-XL-30 may be increased. After regular intake of grapefruit juice, this effect may last for at least three days after the last ingestion of grapefruit juice. Ingestion of grapefruit/grapefruit juice is therefore to be avoided while taking NICARDIA-XL-30.
Other forms of interaction: Taking NICARDIA-XL-30 may increase the spectrophotometric values of urinary vanillylmandelic acid, falsely. However, HPLC measurements are unaffected.
