Usage
Nifedipine is prescribed for:
- Hypertension: To lower blood pressure.
- Chronic Stable Angina: To reduce chest pain frequency and improve exercise tolerance.
- Vasospastic Angina (Prinzmetal’s Angina): To treat chest pain caused by coronary artery spasms.
Pharmacological Classification: Calcium Channel Blocker (Dihydropyridine class)
Mechanism of Action: Nifedipine blocks L-type calcium channels in vascular smooth muscle and myocardium, preventing calcium influx. This leads to vasodilation, reducing peripheral resistance and lowering blood pressure. Coronary artery dilation improves oxygen supply to the heart.
Alternate Names
Nifedipine is the generic name. Brand names include Adalat, Procardia, Nifediac, and others, which can vary regionally.
How It Works
Pharmacodynamics: Nifedipine primarily affects the cardiovascular system by decreasing vascular tone and myocardial contractility.
Pharmacokinetics:
- Absorption: Well-absorbed orally.
- Metabolism: Extensively metabolized by the liver, primarily via CYP3A4 enzymes.
- Elimination: Excreted mainly in the urine as inactive metabolites. The elimination half-life is approximately 2-4 hours, but extended-release formulations provide a longer duration of action.
Mode of Action: Nifedipine selectively blocks L-type calcium channels, inhibiting calcium influx into vascular smooth muscle and cardiac cells during depolarization. This leads to decreased vascular tone, peripheral vasodilation, and reduced myocardial contractility.
Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: Binds to the alpha-1 subunit of L-type calcium channels. Metabolized by CYP3A4.
Elimination Pathways: Primarily hepatic metabolism via CYP3A4 followed by renal excretion of inactive metabolites.
Dosage
Standard Dosage
Adults:
- Hypertension: Extended-release (ER): 30-60 mg orally once daily, titrated up to a maximum of 90-120 mg daily as needed. Immediate-release (IR): 10 mg orally three times a day, titrated up to a maximum of 180 mg/day.
- Angina: ER: 30-60 mg orally once daily, titrated up to a maximum of 120 mg/day as needed. IR: 10 mg three times daily, titrated up to 180 mg daily as needed.
Children:
Use in children is off-label and should be carefully considered. Limited data suggest an initial ER dose of 0.25-0.5 mg/kg/day in one or two divided doses for hypertension, titrated as needed, not to exceed 3 mg/kg/day or 120 mg/day.
Special Cases:
- Elderly Patients: Start with lower doses due to potential age-related decrease in clearance.
- Patients with Renal Impairment: No dose adjustment is typically necessary.
- Patients with Hepatic Dysfunction: Lower initial doses are recommended, and close monitoring is necessary.
- Patients with Comorbid Conditions: Dosage adjustments may be necessary depending on the specific comorbidity. Monitor closely for adverse effects.
Clinical Use Cases
Nifedipine isn’t typically indicated for intubation, surgical procedures, mechanical ventilation, or emergency situations like cardiac arrest. For specific uses like hypertensive emergencies, sublingual or buccal administration of immediate-release nifedipine might be considered in select cases but is generally discouraged due to the risk of profound hypotension.
Dosage Adjustments
Adjustments are based on patient response and tolerance, as well as renal and hepatic function. Gradual titration is generally recommended.
Side Effects
Common Side Effects:
Headache, dizziness, flushing, peripheral edema, palpitations, and fatigue.
Rare but Serious Side Effects:
Hypotension, reflex tachycardia, myocardial infarction, and allergic reactions.
Long-Term Effects:
Potential for chronic complications, such as reflex tachycardia with prolonged use.
Adverse Drug Reactions (ADR):
Severe hypotension, angina exacerbation, and allergic reactions.
Contraindications
- Hypersensitivity to nifedipine or dihydropyridines
- Cardiogenic shock
- Clinically significant aortic stenosis
- Unstable angina
- Pregnancy (before 20 weeks)
- Concomitant use of rifampicin
Drug Interactions
Nifedipine interacts with:
- CYP3A4 Inhibitors (e.g., azole antifungals, macrolide antibiotics, grapefruit juice): Increase nifedipine levels and risk of side effects.
- CYP3A4 Inducers (e.g., rifampin, phenytoin): Decrease nifedipine levels and efficacy.
- Other Antihypertensives: Additive hypotensive effects.
- Beta-blockers: May potentiate bradycardia and heart failure in susceptible individuals.
Pregnancy and Breastfeeding
Nifedipine is contraindicated in early pregnancy (before 20 weeks) and during breastfeeding. It is generally avoided throughout pregnancy due to potential fetal risks.
Drug Profile Summary
- Mechanism of Action: Calcium channel blocker, inhibiting calcium influx and promoting vasodilation.
- Side Effects: Headache, dizziness, flushing, peripheral edema. Serious: Hypotension, MI.
- Contraindications: Hypersensitivity, cardiogenic shock, aortic stenosis, unstable angina, pregnancy, rifampicin use.
- Drug Interactions: CYP3A4 inhibitors/inducers, other antihypertensives, beta-blockers.
- Pregnancy & Breastfeeding: Contraindicated.
- Dosage: Highly variable based on indication, formulation, and patient factors. Requires titration.
- Monitoring Parameters: Blood pressure, heart rate, signs of peripheral edema, liver function tests in patients with hepatic impairment.
Popular Combinations
Nifedipine may be combined with other antihypertensives, such as beta-blockers, ACE inhibitors, or thiazide diuretics, to achieve better blood pressure control.
Precautions
- Monitor blood pressure closely, especially during initial titration.
- Patients with heart failure or severe aortic stenosis should be monitored for worsening of symptoms.
- Avoid abrupt discontinuation, which can lead to rebound hypertension or angina.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Nifedipine?
A: Dosage is highly individualized and dependent on the specific indication (hypertension, angina), formulation (immediate-release vs. extended-release), and patient factors (age, comorbid conditions, other medications).
Q2: What are the common side effects of Nifedipine?
A: Common side effects include headache, dizziness, flushing, peripheral edema, and palpitations.
Q3: How does Nifedipine interact with other medications?
A: It interacts with CYP3A4 inhibitors and inducers, other antihypertensives, and beta-blockers. These interactions can either increase or decrease the efficacy and/or toxicity of Nifedipine.
Q4: Can Nifedipine be used during pregnancy?
A: Nifedipine is generally contraindicated during pregnancy, particularly in the first 20 weeks, due to potential fetal risks.
Q5: What are the contraindications to Nifedipine use?
A: Contraindications include hypersensitivity to nifedipine or other dihydropyridines, cardiogenic shock, significant aortic stenosis, unstable angina, and concomitant use of rifampicin.
Q6: How should Nifedipine be administered?
A: Immediate-release capsules may be taken with or without food. Extended-release tablets should generally be swallowed whole and not crushed, chewed or broken. The timing of administration may vary depending on the specific extended-release product.
Q7: What should patients be monitored for while taking Nifedipine?
A: Blood pressure, heart rate, peripheral edema, and liver function (in patients with hepatic dysfunction) should be monitored.
Q8: Can Nifedipine be used in patients with renal impairment?
A: Generally, no dose adjustment is necessary for patients with renal impairment.
Q9: What are the long-term effects of using Nifedipine?
A: Chronic use may lead to reflex tachycardia.
Q10: Can Nifedipine be used to treat hypertensive emergency?
A: While sublingual or buccal administration of immediate-release nifedipine might be considered in select cases of hypertensive emergency, it is generally discouraged due to potential for profound hypotension. Other agents are preferred.
