Amlodipine, often recognized by the brand name Norvasc, is a commonly prescribed medication used to manage high blood pressure, known as hypertension, and certain types of chest pain, or angina. It belongs to a class of drugs called calcium channel blockers, which work by relaxing the muscles in the walls of blood vessels, thereby lowering blood pressure and increasing blood flow to the heart. When initiating treatment, physicians seek to find the smallest effective dose to achieve the therapeutic goal while minimizing potential side effects.
The Minimum Effective Starting Dose
The lowest commercially available strength of Amlodipine is the 2.5 milligram (mg) tablet, and this is considered the absolute minimum starting dose for adults. While 2.5 mg is the lowest dose, the standard initial dose for most otherwise healthy adults beginning treatment for hypertension is 5 mg once daily. The 2.5 mg dose is specifically reserved for patient populations who may be more sensitive to the blood pressure-lowering effects of the drug, where an overly rapid drop in blood pressure could cause dizziness or other adverse events.
Specific patient groups are routinely started on the 2.5 mg dose to reduce the risk of initial side effects. Older individuals, particularly those over the age of 65, are often prescribed 2.5 mg because they may metabolize the drug more slowly, leading to higher concentrations in the blood. Similarly, patients who are considered small or frail are typically started on the lower dose to prevent an exaggerated response.
Factors Influencing Initial Dose Selection
A patient’s overall health and physiological makeup significantly influence whether a physician chooses the 2.5 mg or 5 mg starting dose. One of the most important considerations is the function of the liver, as Amlodipine is extensively metabolized by this organ. Patients with impaired liver function, or hepatic insufficiency, have a decreased ability to clear the drug, which can prolong its half-life and increase its concentration in the bloodstream. For this reason, a starting dose of 2.5 mg once daily is explicitly recommended for individuals with liver impairment to prevent drug accumulation and potential toxicity.
Additionally, if the patient is already taking other medications that lower blood pressure, such as an ACE inhibitor or a diuretic, a lower starting dose of Amlodipine (2.5 mg) is warranted. Starting low when combining medications minimizes the risk of orthostatic hypotension, which is a sudden drop in blood pressure upon standing.
The Process of Dose Adjustment (Titration)
Once an initial dose is selected, the patient begins the process of dose adjustment, known as titration, which involves gradually increasing the medication until the desired blood pressure target is achieved. Amlodipine has a long elimination half-life, typically ranging from 30 to 50 hours, which is why it is taken only once daily and requires a slow titration schedule. This long half-life means that it takes seven to eight days of consecutive daily dosing for the drug to reach steady-state plasma levels in the body.
Because of this slow accumulation, dose changes are not made immediately; instead, physicians generally wait 7 to 14 days between any titration steps to accurately assess the full therapeutic effect of the current dose. The standard maintenance dose range for most adults is typically between 5 mg and 10 mg once daily. For patients whose blood pressure remains uncontrolled on 5 mg after the assessment period, the dose may be increased to 10 mg.
It is important to note that 10 mg once daily is the maximum recommended dose of Amlodipine for adults. Doses higher than this have not shown additional benefit for blood pressure reduction and may increase the risk of adverse effects. Throughout this adjustment phase, regular monitoring of blood pressure is essential to confirm the drug’s effectiveness and to guide the physician in determining the optimal, individualized dose.