What Factors Affect a Sufficient Nifedipine Dose?

Nifedipine, also sold under the brand names Procardia®, Adalat®, Nifediac®, Nifedical®, and Cordipin® is a dihydropyridine drug used predominantly in the treatment of angina, which is chest pain, and high blood pressure. Like many other members of the calcium channel blocker class of medications, nifedipine is sometimes used to treat a wide variety of other conditions, such as the esophageal spasticity sometimes produced by cancer or tetanus, congestive heart failure, migraine prevention, Raynaud's syndrome, premature labor, and hypertrophic cardiomyopathy in children. The recommended initial nifedipine dose varies according to the age of the patient, the condition being treated, the form of the medication prescribed, and the condition of the liver. If the patient is taking other medications in addition to this medication, drug interactions may make it necessary to adjust the standard dose.

When using this medication to treat high blood pressure in adults, an initial oral nifedipine dose of 30 to 60 mg should be given once per day. Increases can be made to the dose once every one or two weeks up to a maximum dose of 90 mg per day of Adalat® or 120 mg per day of Procardia®, according to the recommendations of the manufacturer. IAs of 2011, it has not been approved for the treatment of high blood pressure in pediatric patients.

The standard initial nifedipine dose used for the prevention of angina pectoris is 10 mg given orally three times per day. The dose for extended release tablets is between 30 mg and 60 mg given daily. Nifedipine is not equivalent to nitroglycerin and should not be administered to treat an acute attack of angina. The dose may be cautiously adjusted upward every 7 to 14 days. The dose for the treatment of migraines is the same as that for the treatment of angina. Since nifedipine doses greater than 30 mg per day have not been shown to produce any greater clinical benefit, increases to the standard initial dose are not recommended.

An initial oral nifedipine dose of 30 mg once daily in the form of Adalat (R) CC® or 30 mg to 60 mg in the form of Procardia XL® is recommended for treatment of congestive heart failure. Dosage increase is not recommended, nor are daily maintenance doses. Neither have been shown to produce significant clinical improvement over the standard dose.

When administering nifedipine to treat hypertrophic cardiomyopathy in pediatric patients, the appropriate nifedipine dose is best calculated according to body weight. Between 0.6 mg and 0.9 mg per kilogram should be given during a 24-hour period. The total daily dose should be divided into three or four separate doses given through out the day. The smallest possible effective dose should be given, as the side effects of nifedipine increase linearly with the dosage.

The most common side effects include headache, fatigue, dizziness, nausea, constipation, insomnia, rash, itching, and joint or muscle pain. People who are pregnant or who may become pregnant should be informed that one of the side effects of nifedipine is potential fetal injury or death. In animal studies, the fetotoxic effects were found to be dose-dependent, with higher doses dramatically increasing the risk of injury to the fetus. The drug should only be administered during pregnancy if the health risk to the mother overshadows the risk to the fetus.

Despite the pharmacokinetics of nifedipine, it is not believed to interact seriously with warfarin, digoxin, coumarin, or quinidine, nor with most beta-adrenergic blocking agents, which are also known as beta-blockers. The coadministration of nifedipine along with cimetidine is known to produce higher blood plasma levels of the latter drug, one of the more serious of nifedipine drug interactions. Due to its cytochrome P450 3A4 (CYP3A4) liver enzyme inhibiting activity, patients taking nifedipine should completely abstain from consuming products containing grapefruit or grapefruit juice, as they may cause overdose. Other herb and drug interactions include acarbose, nefazadone, narcotic pain medications like fentanyl, St. John's wort, rifabutin, rifampin, rifapentine, synthetic antibiotics like clarithromycin, antifungal medications like fluconazole, many AIDS medications like atazanavir, immunosuppressant drugs like tacrolimus, some medications used in the treatment of high blood pressure, and seizure-preventative drugs like phenobarbital.