What is Nifedipine Used For? Uses, Dosage, & Side Effects

Nifedipine is a medication classified as a calcium channel blocker, specifically within the dihydropyridine group. It plays a significant role in managing hypertension and angina. This article details the uses of nifedipine, its mechanism of action, how it’s administered, potential adverse effects, contraindications, and monitoring guidelines, providing healthcare professionals with essential information for effective patient care.

Indications for Nifedipine

Nifedipine, a dihydropyridine calcium channel blocker, is primarily prescribed as an antihypertensive and antianginal medication.

FDA-Approved Uses:

• Chronic Stable Angina: Nifedipine has been shown to reduce the frequency of angina episodes and improve exercise tolerance. To counteract potential reflex tachycardia, combining nifedipine with a beta-blocker is often recommended. A long-acting formulation (extended-release) is preferred.
• Vasospastic Angina: Nifedipine can be used as a second-line treatment for vasospastic angina.
• Hypertension: Nifedipine can be used alone or with other medications like ACE inhibitors, ARBs, or thiazide diuretics to manage high blood pressure.

Image alt text: Nifedipine capsules, a medication commonly used to treat hypertension and angina.

Off-Label Uses:

• Raynaud’s phenomenon
• Severe hypertension during pregnancy and postpartum hypertension
• High altitude pulmonary edema
• Pulmonary arterial hypertension (group 1)
• Achalasia
• Distal ureteric calculi
• Tocolysis

How Nifedipine Works

Nifedipine’s mechanism of action involves inhibiting calcium influx into smooth muscle cells. During depolarization, calcium ions enter through voltage-gated channels. Nifedipine blocks these L-type calcium channels in vascular smooth muscle and myocardial cells, reducing intracellular calcium. This leads to decreased peripheral arterial vascular resistance, dilation of coronary arteries, reduced systemic blood pressure, and increased myocardial oxygen delivery. Consequently, nifedipine exhibits both hypotensive and antianginal properties.

How Nifedipine is Administered

Nifedipine is available in immediate-release and extended-release formulations. Initially, it was marketed as a short-acting, immediate-release formulation, requiring multiple daily doses. This led to rapid vasodilation and reflex sympathetic activation, causing side effects like headaches, palpitations, and flushing. Extended-release preparations were developed to provide a sustained 24-hour antihypertensive effect and reduce side effects.

Extended-release tablets are available in 30, 60, and 90 mg strengths. Dosage adjustments should occur at 7- to 14-day intervals. When switching from immediate-release to extended-release, the total daily dosage should remain the same. Immediate-release formulations can be taken without regard to meals, while some extended-release preparations require ingestion on an empty stomach.

Immediate-release nifedipine has an onset of action within 20 minutes and a half-life of 4 to 7 hours. Extended-release formulations last approximately 24 hours. Nifedipine is metabolized hepatically via the CYP3A4 pathway. Extended-release preparations have a bioavailability of up to 89% compared to immediate-release. Bioavailability significantly increases in patients with liver failure, requiring dosage adjustments due to reduced medication clearance.

Recommended Dosages:

• Chronic Stable Angina:
  • Immediate-release: 10 to 20 mg three times daily; maximum dose of 180 mg per day
  • Extended-release: 30 or 60 mg daily; maximum dose of 120 mg per day
• Vasospastic Angina:
  • Extended-release: 30 or 60 mg daily; maximum dose of 120 mg per day
• Hypertension:
  • Extended-release: 30 or 60 mg daily; maximum dose of 120 mg per day
• Hypertensive Emergency During Pregnancy or Postpartum Period:
  • Immediate-release: 10 mg; may repeat with a 20 mg dose in 20 minutes

Potential Adverse Effects of Nifedipine

Adverse effects occur in approximately 20 to 30% of patients taking nifedipine, primarily due to its vasodilatory properties.

Common side effects include flushing, peripheral edema, dizziness, and headache. Extended-release preparations are generally better tolerated than immediate-release formulations. Hypersensitivity reactions, such as pruritus, urticaria, and bronchospasms, are relatively rare. Abruptly stopping nifedipine after prolonged use can lead to rebound hypertension or angina.

Image alt text: Lower extremity edema in patient; Peripheral edema is a known side effect of nifedipine.

Nifedipine Contraindications

• Absolute Contraindications:
  • Hypersensitivity to nifedipine or its components
  • ST-elevation myocardial infarction (STEMI)
• Relative Contraindications:
  • Severe aortic stenosis
  • Unstable angina
  • Hypotension
  • Heart failure
  • Moderate to severe hepatic impairment

Immediate-release nifedipine is not recommended for unstable angina/non-STEMI unless combined with a beta-blocker. Immediate-release preparations should be avoided in hypertensive emergencies as they are neither safe nor effective. In cardiogenic shock, nifedipine can worsen the condition by inhibiting calcium influx into cardiac cells. In severe aortic stenosis, it can cause ventricular collapse and dysfunction. In unstable angina, it can increase cardiac contractility, raising myocardial oxygen demand. Nifedipine can exacerbate hypoperfusion to vital organs in patients with severe hypotension. Patients with hepatic impairment may experience a longer half-life, increasing the risk of toxicity and side effects.

Monitoring Nifedipine Treatment

Routine laboratory monitoring is generally not required for patients taking nifedipine. However, as it is an antihypertensive medication, regular blood pressure monitoring is essential to achieve target levels. Patients should also be monitored for adverse effects such as peripheral edema, dizziness, and flushing.

Managing Nifedipine Toxicity

Nifedipine overdose treatment depends on the amount ingested, time since ingestion, patient age, and comorbidities. Initial assessment includes securing airway, breathing, circulation, and obtaining blood work to test for coingestants. Early consultation with poison control/toxicology is crucial.

Overdose can lead to systemic vasodilation, severe hypotension, and reflex tachycardia, potentially progressing to shock and death. Activated charcoal (1 g/kg) is useful if the patient presents within 1 to 2 hours of ingestion. Whole bowel irrigation should be considered for extended-release preparations or large quantities ingested. Nasogastric lavage is usually ineffective. Treatment includes intravenous fluid resuscitation, calcium salts, and vasopressor therapy with dopamine or norepinephrine. High-dose insulin can also be considered. Continuous monitoring of electrocardiographic results, vital signs, kidney function, urine output, and electrolytes is necessary. Psychiatric consultation is also needed for intentional ingestion. Patients overdosing on immediate-release preparations require observation for 4 to 7 hours, while those on extended-release require 24 hours of telemetry observation.

There is no specific antidote for nifedipine overdose.

Enhancing Healthcare Team Outcomes

All members of the interprofessional healthcare team should understand the indications and contraindications of nifedipine. Clinicians (including specialists, NPs, and PAs), nurses, and pharmacists should be familiar with the drug. Due to the risk of severe hypotension, dosing should be carefully titrated from a low initial dose. Long-term patient monitoring is necessary to assess effectiveness. Sublingual preparations are no longer recommended for hypertensive emergencies due to a lack of efficacy and severe adverse events.

Prescribing clinicians should collaborate with the interprofessional team when using nifedipine. Pharmacists should verify dosing, especially given the differences between release formulations, and conduct medication reconciliation to identify potential drug-drug interactions. Nurses administer the drug inpatient and are crucial for observing treatment effectiveness and adverse events, reporting them to the clinician immediately. This collaborative approach enhances patient outcomes with nifedipine therapy.

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