Adalat OROS and Nifedipine: Identical Mechanism of Action
Adalat OROS and nifedipine have the exact same mechanism of action because Adalat OROS is simply a sustained-release formulation of nifedipine—they are the same drug. The only difference lies in the drug delivery system, not the pharmacological mechanism.
Core Mechanism of Action
Both Adalat OROS and standard nifedipine work through the following mechanisms:
- Inhibition of L-type voltage-dependent calcium channels, which blocks calcium influx into vascular and cardiac smooth muscle cells 1
- Peripheral arterial vasodilation, producing the most pronounced vasodilatory effects among all calcium channel blockers 2
- Coronary artery dilation, providing anti-ischemic effects through improved myocardial oxygen supply 2
- Reduction in afterload, decreasing myocardial oxygen demand 2
- Minimal effects on AV conduction or sinus node function, unlike non-dihydropyridine calcium channel blockers 2
Secondary Cardiovascular Effects
The vasodilation triggers a compensatory response:
- Baroreceptor-mediated sympathetic activation occurs in response to the blood pressure drop, leading to reflex tachycardia and increased cardiac output 1
- This indirect cardiostimulation can be problematic, which is why immediate-release nifedipine must be avoided without concomitant beta-blockade 2, 3
The OROS Difference: Delivery, Not Mechanism
The GITS (Gastrointestinal Therapeutic System) or OROS technology in Adalat OROS:
- Provides once-daily sustained release of nifedipine over 24 hours 4
- Eliminates the rapid peaks and troughs seen with immediate-release formulations 4
- Does not alter the fundamental calcium channel blocking mechanism 4
- Reduces the risk of reflex tachycardia and hypotensive episodes associated with rapid-release preparations 2
Critical Clinical Distinctions
Immediate-release nifedipine carries significant risks that sustained-release formulations like Adalat OROS mitigate:
- The Holland Interuniversity Nifedipine/Metoprolol Trial (HINT) was stopped early due to excess reinfarctions with immediate-release nifedipine 2
- Rapid-release, short-acting nifedipine must be avoided in acute coronary syndromes without beta-blockade due to increased adverse potential 2, 3
- Sustained-release formulations like Adalat OROS (nifedipine GITS) demonstrate comparable efficacy to other long-acting dihydropyridines like amlodipine, with similar safety profiles 4
Additional Pharmacological Properties
Beyond calcium channel blockade, nifedipine has been shown to:
- Produce nitric oxide, contributing to its vasodilatory effects 5
- Potentially facilitate neurotransmitter release through calcium-independent mechanisms at higher doses, though this is not clinically relevant at therapeutic concentrations 5
Bottom Line
Adalat OROS and nifedipine share identical mechanisms—L-type calcium channel blockade leading to vasodilation. The OROS formulation simply provides sustained drug delivery to avoid the dangerous hemodynamic fluctuations of immediate-release preparations while maintaining the same fundamental pharmacology 1, 4.