The key difference between Nifedipine and Amlodipine is that Nifedipine is a first-generation calcium channel blocker with a shorter half-life and a shorter duration of action. In comparison, Amlodipine is a third-generation calcium channel blocker with a longer half-life and extended duration of action.
Nifedipine and Amlodipine are calcium channel blockers in cardiovascular disorders such as vasospastic angina, chronic stable angina, and hypertension. Calcium plays a vital role in the contractility of vascular smooth muscle and myocardial cells. In myocardial cells, calcium entry initiates the calcium-troponin complex’s formation, enabling the interaction between actin and myosin, which leads to contraction. Conversely, in vascular smooth muscle cells, a similar sequence of events occurs, but the calcium-calmodulin complex is formed instead of the calcium-troponin complex. Both nifedipine and amlodipine function by blocking the receptors of the L-type calcium channel, gradually reducing the high threshold current in cardiac cells. Although these medications have similar mechanisms of action, they exhibit notable differences in chemical structures, pharmacokinetics, duration of action, and available dosage forms.
CONTENT
1. Overview and Key Difference
2. What is Nifedipine
3. What is Amlodipine
4. Similarities – Nifedipine and Amlodipine
5. Nifedipine vs Amlodipine in Tabular Form
6. Summary – Nifedipine vs Amlodipine
What is Nifedipine?
Nifedipine is a first-generation calcium channel blocker belonging to the dihydropyridine drug class. It is mainly prescribed to manage angina pectoris and hypertension. Nifedipine blocks voltage-gated calcium channels to prevent the entry of calcium ions in both vascular smooth muscle and myocardial cells. This reduces arterial vascular resistance and dilated coronary arteries, ultimately lowering blood pressure and increasing the oxygen supply to the heart.
Figure 01: Chemical Structure of Nifedipine
Nifedipine is available in sublingual and oral forms and is completely absorbed in the gastrointestinal tract. However, bioavailability is decreased due to first-pass metabolism. Most of the nifedipines in the blood remain bound with plasma proteins. CYP3A4 predominantly metabolizes the drug in the liver. The inactive water-soluble metabolites are excreted in the urine, while feces eliminate the rest.
What is Amlodipine?
Amlodipine is a third-generation calcium channel blocker used to treat angina and hypertension. It acts as a dihydropyridine calcium antagonist to inhibit the calcium influx into vascular smooth muscle and myocardial cells. This result in a dilating effect on peripheral arterioles and reduced resistance against the cardiac muscle function. In addition, it has been observed that the administration of Amlodipine leads to dilation of the main coronary arteries and arterioles. Amlodipine is also considered a powerful antioxidant since it induces the production of nitric oxide synthase (NO), contributing to the vasodilatory effect.
Figure 02: Chemical Structure of Amlodipine
Amlodipine is also completely but slowly absorbed in the gastrointestinal tract upon oral administration. The circulating drug is bound with the plasma proteins and extensively metabolized in the liver. The urine primarily excretes the metabolized and unchanged drug. Animal studies related to Amlodipine have investigated that there is no carcinogenic, mutagenic, or fertility effect of Amlodipine in mice models, displaying the safety and absence of toxicity. However, the safety of Amlodipine in human pregnancy has not been well studied, and therefore, it is still considered a pregnancy type C drug.
What are the Similarities Between Nifedipine and Amlodipine?
- Nifedipine and Amlodipine are calcium channel blockers.
- They selectively target the L-type calcium channels to inhibit the calcium influx into cardiac cells, thereby regulating blood pressure.
- Both medications are widely used to manage hypertension by relaxing and widening blood vessels.
- Nifedipine and Amlodipine effectively treat other cardiovascular conditions, such as angina.
- Both drugs are available in oral formulations and can be taken with or without food.
What is the Difference Between Nifedipine and Amlodipine?
Nifedipine and Amlodipine are calcium channel blockers primarily used to inhibit calcium influx. They manage hypertension by relaxing and widening the blood vessels. Nevertheless, there is a distinct difference between Nifedipine and Amlodipine. Nifedipine is a first-generation calcium channel blocker with a shorter half-life and a shorter duration of action. In contrast, Amlodipine is a third-generation calcium channel blocker with a longer half-life and extended duration of action.
Moreover, Nifedipine is available in immediate-release and extended-release formulations, while Amlodipine is primarily available as a once-daily tablet. Nevertheless, both medications are prescribed mainly for managing hypertension and angina. Amlodipine is also used for coronary artery disease. Unlike Nifedipine, Amlodipine can promote the synthesis of nitric oxide synthase (NO) to further support the amlodipine-mediated vasodilatory effect. However, it is important to note that while these differences exist, Nifedipine and Amlodipine are effective medications for managing hypertension and other cardiovascular conditions.
Below is a summary of the difference between Nifedipine and Amlodipine in tabular form for side-by-side comparison.
Summary – Nifedipine vs Amlodipine
Nifedipine and Amlodipine are calcium channel blockers primarily used for treating cardiovascular conditions such as hypertension and angina. Nifedipine is a first-generation dihydropyridine calcium channel blocker with a shorter half-life and is available in immediate-release and extended-release formulations. In contrast, Amlodipine, a third-generation calcium channel blocker, has a longer half-life and has sustained antihypertensive effects. It is primarily available as a once-daily tablet. Thus, this is the key difference between Nifedipine and Amlodipine. While both medications block calcium influx into cardiac and smooth muscle cells, Amlodipine has a broader range of indications, including vasospastic angina and coronary artery disease. The choice between the two depends on individual patient factors and should be made in consultation with a healthcare professional.
Reference:
1. Geijn, Herman P., et al. “Nifedipine Trials: Effectiveness and Safety Aspects.” BJOG: An International Journal of Obstetrics & Gynaecology, vol. 112, 2005, pp. 79–83.
2. Fares, Hassan, et al. “Amlodipine in Hypertension: A First-Line Agent with Efficacy for Improving Blood Pressure and Patient Outcomes.” Open Heart, vol. 3, no. 2, 2016.
Image Courtesy:
1. “Nifedipine Structure” By 陳弈豪 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “S-Amlodipine” By Chandrashekharborkar – Own work (CC BY 3.0) via Commons Wikimedia