Drugs affecting nifedipine
Nifedipine is metabolized with isoenzyme CYP3A4 system of cytochrome P450, located in the intestinal mucosa and in the liver.
Drugs that suppress or induce this enzyme system can affect the effect of "primary transmission" (after ingestion) or clearance of nifedipine (see section Special instructions).
Consider the strength of the interaction and the duration of this effect when taking nifedipine simultaneously with the following drugs
Rifampicin
Rifampicin greatly increases the activity of the isoenzyme CYP3A4 system of cytochrome P450, which leads to a significant decrease in the bioavailability and effectiveness of nifedipine, so their simultaneous administration is contraindicated (see section Contraindications).
In the period of simultaneous application of nifedipine with the following weak or moderate inhibitors of the isoenzyme CYP3A4 should monitor blood pressure and, if necessary, adjust the dose of the drug Nifedipine (see section Method of administration and dose).
Macrolides (for example, erythromycin)
There have been no studies of the interaction between nifedipine and macrolides. It is known that some macrolides can inhibit the isoenzyme CYP3A4, which takes part in the metabolism of other drugs.Therefore, the potential increase in the concentration of nifedipine in blood plasma can not be ruled out when they are simultaneously taken (see section Special instructions).
Azithromycin does not inhibit isoenzyme CYP3A4, although it belongs in its structure to macrolide antibiotics.
Inhibitors of HIV proteases (eg, ritonavir, indinavir, nelfinavir, amprenavir)
Clinical studies of the interaction between nifedipine and HIV protease inhibitors have not been presented. It is known that preparations of this class inhibit isoenzyme CYP3A4. It has also been shown that this class of drugs inhibits isoenzyme CYP3A4 in vitro, which causes the metabolism of nifedipine. With simultaneous administration with nifedipine, one can not exclude a significant increase in its concentration in the blood plasma by reducing the effect of "primary transmission" and reducing its excretion (see section Special instructions).
Azole antifungal agents (for example, ketoconazole, fluconazole, itraconazole)
Clinical studies of the interaction between nifedipine and azole antifungal agents are not yet available. It is known that preparations of this class inhibit isoenzyme CYP3A4. With simultaneous ingestion with nifedipine, one can not exclude a significant increase in its systemic bioavailability due to a decrease in the effect of "primary transmission" (see section Special instructions).
Fluoxetine
Clinical studies of the interaction between nifedipine and fluoxetine are not presented. It is known that fluoxetine inhibits in vitro isoenzyme CYP3A4, which causes the metabolism of nifedipine. Therefore, it is not possible to exclude an increase in the concentration of nifedipine in blood plasma when they are simultaneously taken (see section Special instructions).
Nefazodone
Clinical studies of the interaction between nifedipine and nefazodone have not yet been presented. It is known that nefazodone inhibits isoenzyme CYP3A4, which causes the metabolism of nifedipine. Therefore, it is not possible to exclude an increase in the concentration of nifedipine in blood plasma when they are simultaneously taken (see section Special instructions).
Hinupristin / Dalfopristin
Simultaneous administration of quinupristin / dalfopristin with nifedipine may lead to an increase in the concentration of nifedipine in the blood plasma (see section Special instructions).
Valproic acid
Clinical studies of potentialinteractions between nifedipine and valproic acid are not reported. Since it was found that valproic acid can increase the concentration of a similar in structure BCCC, nimodipine, in blood plasma, we can not exclude an increase in the concentration of nifedipine in the blood plasma and as a result - enhance its therapeutic effect (see section Special instructions).
Cimetidine
In view of inhibition of the isoenzyme CYP3A4 cimetidine increases the concentration of nifedipine in the blood plasma and may enhance the antihypertensive effect (see section Special instructions).
Other types of interaction
Cisapride
Simultaneous administration of cisapride and nifedipine may increase the concentration of nifedipine in the blood plasma.
Inductors of isoenzyme CYP3A4 cytochrome P450, including antiepileptic drugs, such as phenytoin, carbamazet and phenobarbital
Phenytoin induces isoenzyme CYP3A4. With the simultaneous use of nifedipine with phenytoin, the bioavailability of nifedipine decreases and, thus, its effectiveness decreases. At simultaneous reception of these preparations it is necessary to estimate clinical effect of nifedipine and, if necessary, it is recommended increase its dose.If the dose of nifedipine is increased during simultaneous administration of both drugs, a reduction in the dose of nifedipine after the withdrawal of phenytoin is required. Clinical studies of the potential interaction between nifedipine and carbamazepine or phenobarbital are not available. Since it has been established that in view of the induction of enzymes, both drugs can reduce the concentration of a similar BMSC, nimodipine, in the blood plasma, it can not be ruled out that the concentration of nifedipine in the blood plasma decreases, and as a result, its therapeutic effect is reduced.
Effect of nifedipine on other drugs:
Preparations, lowering blood pressure
Joint use of nifedipine with other antihypertensive drugs can lead to mutual enhancement of the antihypertensive effect, such drugs, for example, include:
- Diuretics,
- Beta-blockers,
- Angiotensin converting enzyme inhibitors,
- Angiotensin I receptor antagonists,
- BCCI,
- Alfa-adrenoblockers,
- Inhibitors of phosphodiesterase type 5,
- Methyldopa,
- Magnesium sulfate.
With the simultaneous use of nifedipine and beta-blockers, patients should be carefully monitored,since in some cases, the progression of chronic heart failure may be aggravated.
Digoxin
The simultaneous use of nifedipine and digoxin can lead to a decrease in digoxin clearance and, as a consequence, an increase in its concentration in the blood plasma. Care should be taken to monitor the patient for signs of digoxin overdose and, if necessary, reduce the dose of digoxin, taking into account its concentration in the blood plasma.
Quinidine
When combined with quinidine in some patients, its concentration in the blood plasma may decrease, and later on, when nifedipine is discontinued, it can significantly increase. Therefore, with the simultaneous administration of nifedipine or its withdrawal after co-administration with quinidine, it is recommended to carefully monitor the concentration of quinidine in the blood plasma and, if necessary, adjust its dose. There was also reported an increase in the concentration of nifedipine in blood plasma during the simultaneous use of drugs, while some patients did not observe a change in the pharmacokinetic parameters of nifedipine.When adding quinidine to therapy with nifedipine, you should monitor BP and, if necessary, it is recommended to reduce the dose of nifedipine.
Tacrolimus
Tacrolimus is metabolized by isoenzyme CYP3A4 cytochrome P450. Recently published data indicate that the dose of tacrolimus in the case of simultaneous administration with nifedipine in some patients may be reduced. With simultaneous administration of drugs should monitor the concentration of tacrolimus in the blood plasma, and if necessary, it is recommended to reduce its dose.
Grapefruit juice
Grapefruit juice inhibits isoenzyme CYP3A4 systems of cytochrome P450. Taking nifedipine along with grapefruit juice can lead to an increase in the plasma concentration of nifedipine and an increase in its effect as a result of reduced metabolism when it is "first passed through the liver" or lowered the clearance. This can lead to an increase in the antihypertensive effect of nifedipine. With the regular intake of grapefruit juice, this effect can last at least 3 days after its last reception. Avoid taking grapefruit juice while taking nifedipine (see section Method of administration and dose).
Other forms of interaction
Nifedipine can cause a false increase in the concentration of vanillylmandelic acid in urine when determined spectrophotometrically, but does not affect the results of measurements using the HPLC method.