Nifedipine

Drug Information: Nifedipine

Nifedipine is a dihydropyridine calcium channel blocker primarily used to manage hypertension and angina. It works by inhibiting the influx of calcium ions into vascular smooth muscle cells and cardiac myocytes, leading to vasodilation and reduced blood pressure. Nifedipine is available in both immediate-release and extended-release formulations, allowing for flexible dosing regimens. Its use requires careful monitoring, especially in patients with pre-existing cardiovascular conditions.

Category

Antihypertensive

Mechanism of Action

Nifedipine is a calcium channel blocker belonging to the dihydropyridine class. It selectively inhibits the transmembrane influx of calcium ions into vascular smooth muscle and, to a lesser extent, cardiac muscle. This inhibition occurs by binding to L-type calcium channels. By reducing calcium influx, nifedipine prevents the depolarization and subsequent contraction of these muscle cells. In vascular smooth muscle, this leads to vasodilation, reducing peripheral vascular resistance and lowering blood pressure. The reduced afterload on the heart also decreases cardiac workload and oxygen demand. The selectivity for vascular smooth muscle over cardiac muscle means nifedipine has less of an effect on cardiac contractility and heart rate compared to non-dihydropyridine calcium channel blockers like verapamil or diltiazem. This makes it particularly useful in treating hypertension and certain types of angina where vasodilation is the primary therapeutic goal. Furthermore, the extended-release formulations of nifedipine provide a more gradual and sustained reduction in blood pressure, minimizing the reflex tachycardia that can sometimes occur with immediate-release formulations.

Clinical Uses

Nifedipine is primarily used in the management of hypertension, both as monotherapy or in combination with other antihypertensive agents. It is effective in reducing systolic and diastolic blood pressure, thereby decreasing the risk of cardiovascular events such as stroke and myocardial infarction. Nifedipine is also indicated for the treatment of various forms of angina pectoris, including chronic stable angina (angina of effort) and vasospastic angina (Prinzmetal’s angina). In angina, it reduces the frequency and severity of chest pain by dilating coronary arteries and decreasing myocardial oxygen demand. Off-label uses include the treatment of Raynaud’s phenomenon, where it helps improve blood flow to the extremities, and the management of premature labor by inhibiting uterine contractions. However, the use of nifedipine in pregnancy should be carefully considered due to potential risks. Its effectiveness and safety have been well-established in clinical trials, making it a valuable option in the treatment of these conditions.

Dosage

Adults:
* Hypertension: The usual starting dose for extended-release nifedipine is 30 mg once daily. The dose can be adjusted based on individual response, typically up to a maximum of 90 mg once daily. Immediate-release formulations are generally not recommended for chronic hypertension management due to the risk of rapid blood pressure drops and associated adverse effects.
* Angina: For chronic stable angina, extended-release nifedipine is typically initiated at 30 mg once daily, with adjustments based on symptom control and tolerability.

Pediatrics:
The use of nifedipine in pediatric patients is generally off-label and should be reserved for situations where other antihypertensive agents are not effective or tolerated. Dosing must be carefully individualized by a specialist.

Route of Administration:
Nifedipine is administered orally. Extended-release tablets should be swallowed whole and not crushed or chewed.

Indications

* Hypertension (high blood pressure)
* Chronic Stable Angina (chest pain)
* Vasospastic Angina (Prinzmetal’s angina)
* Raynaud’s phenomenon (off-label use)
* Premature labor (off-label use, with caution)

Contraindications

* Hypersensitivity to nifedipine or other dihydropyridines.
* Cardiogenic shock.
* Advanced aortic stenosis.
* Acute myocardial infarction (within the first few weeks).
* Unstable angina.
* Use with rifampin (due to significant drug interaction).

FAQ

Q: What is nifedipine used for?
A: Nifedipine is primarily used to treat high blood pressure (hypertension) and different types of angina (chest pain).

Q: How does nifedipine work?
A: Nifedipine is a calcium channel blocker. It works by relaxing blood vessels so blood can flow more easily, lowering blood pressure and reducing the heart’s workload.

Q: What are the common side effects of nifedipine?
A: Common side effects include headache, flushing, dizziness, peripheral edema (swelling of ankles and feet), and palpitations.

Q: Can I take nifedipine if I am pregnant?
A: You should discuss the use of nifedipine during pregnancy with your doctor. While it can be used in certain situations, there are potential risks to consider.

Q: How should I take nifedipine?
A: Take nifedipine exactly as prescribed by your doctor. Extended-release tablets should be swallowed whole and not crushed or chewed. It can be taken with or without food.

Q: What should I avoid while taking nifedipine?
A: Avoid drinking grapefruit juice, as it can increase the levels of nifedipine in your blood, potentially leading to increased side effects. Also, avoid alcohol, as it can lower blood pressure and increase the risk of dizziness.

Q: What should I do if I miss a dose of nifedipine?
A: If you miss a dose, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to catch up.

Q: Is nifedipine a beta blocker?
A: No, nifedipine is a calcium channel blocker, not a beta blocker. They work through different mechanisms to lower blood pressure.