Amlodipine: Mechanism of Action, Indications, Dosage, Side Effects, Precautions and Interactions

It belongs to the group of dihydropyridines, which act in muscle contraction.

These affect the relaxation of blood vessels , which can reduce the workload of the heart.

Amlodipine is an antagonist, which blocks the calcium ion channels, blocking them in the cardiac smooth muscle membrane, influencing the amount of calcium present in the cells and muscles of the heart.

This medication lowers blood pressure, and its antihypertensive action is associated with this relaxing effect of blood vessels of vascular smooth muscle, allowing blood to flow more easily.

Chemical formula

  • C20H25N2ClO5.
  • (RS)-3-etil-5-metil-2-(2-aminoetoximetil)-4-(2-chlorofenil)-1,4-dihidro-6-metil-3,5- piridinadicarboxilato.

Presentation

  • Tablets of 5 mg and 10 mg.

Mechanism of action

Amlodipine inhibits the flow through the cell membrane of calcium ions, because it binds by changing its affinity, to the alpha1 subunit of L-type calcium channels, preventing its opening.

This results in a reduction in the entry of calcium ions, modifying the contractility of the heart muscle and smooth muscle.

Those who depend on the movement of these extracellular calcium ions from cardiac or muscle cells through specific channels, for cardiac contractility and oxygen demand.

Because it is a peripheral arterial vasodilator, it acts immediately on vascular smooth muscle, decreasing peripheral vascular resistance and consequently blood pressure.

It can also dilate the coronary arteries and arterioles, thereby decreasing total peripheral resistance.

Because the heart rate remains stable, this relief of the heart decreases the energy consumption in the myocardium, it also reduces the need for oxygen.

Indications

This drug is indicated for the treatment of coronary diseases such as chronic stable angina (due to physical or emotional stress) and vasospastic angina (Prinzmetal’s angina or variant angina) and in the management of arterial hypertension .

Dose

In adults: Initially a dose of 5 mg / day is recommended once a day.

The maximum antihypertensive effects usually take weeks to be fully instituted and in case of increasing the dose can not exceed 10 mg / day.

In patients who have liver insufficiencies, the first doses should be reduced by half.

In older adults, the first doses should be 2.5 mg once a day, adjusting the dose every seven to fourteen days, depending on the patient’s responses and tolerance.

In children and adolescents from 6 to 17 years of age the recommended dose as oral antihypertensive is 2.5 mg once a day as the initial dose.

If the goal of blood pressure is not reached after 4 weeks, it rises to 5 mg, in children under 6 years, the starting dose is 0.05-0.1 mg / kg / day.

Increasing after a week of starting the treatment, little by little at a maximum dose of 0.6 mg / kg / day.

In order to remember your administration, it can be administered at the same time every day.

Side effects

Amlodipine is generally very well tolerated in doses that do not exceed 10 mg / day.

Mild adverse reactions have been reported almost always linked with peripheral vasodilatory effects of this drug.

Migraines and edema are two of the most common side effects.

The presence of dizziness, weakness, palpitations and hot flushes that are usually related to the doses have also been reported.

Likewise, there have been reports of jaundice and elevated transaminases, consistent with the appearance of hepatitis or cholestasis in few patients.

There have been very rare cases of pancreatitis.

There are reports of other rare side effects such as allergic reactions, angioedema and erythema multiforme.

The cases of intense pruritus associated with amlodipine that have been reported disappeared when the treatment was discontinued.

In a very small number cases have been reported gynecomastia, sinus bradycardia, tremor, vasculitis , angina, peripheral neuropathy, peripheral ischemia, orthostatic hypotension , syncope , paresthesias , anorexia, dysphagia .

Also cases of vertigo, blurred vision, constipation, diarrhea and flatulence, but its relationship with the amlodipine has not been established with certainty.

Precautions and contraindications

Amlodipine is organically related to nifedipine (1,4-dihydropyridine) and is not recommended in patients who are sensitive to the types of dihydropyridines.

Amlodipine should be used with caution in cases of patients who have severe bradycardia or the presence of heart failure (especially when associated with a β-blocker) due to the eventuality of cardiogenic shock, since it has negative inotropic properties and its effective hypotensive effects.

Patients suffering from left ventricular dysfunction who are prescribed amlodipine for angina treatments have to be constantly monitored to show that the medication does not aggravate heart failure .

Amlodipinone should be prescribed in patients who have Class IV heart failure, according to the New York Heart Association.

Amlodipine is a powerful hypotensor, it should not be administered in patients with systolic blood pressure less than 90 mmHg.

In case of liver failure , as occurs with calcium channel blockers, the half-life of amlodipine is prolonged in patients with variation in liver function.

Since the amlodipine is metabolized by means of this route, and indications for its dosage have not yet been established.

Therefore, in these patients, the doses should be adjusted according to the response of the patient, starting treatment with lower doses than those recommended in normal adults.

Amlodipine is partially contraindicated in patients suffering from advanced aortic stenosis because the pressure difference associated with this condition may worsen.

Amlodipine is located in category C risk in the case of pregnancy.

This drug can only be administered when the benefits clearly outweigh the potential risks.

It is unknown if the drug manages to pass through breast milk, so it is recommended to avoid during the period of lactation.

Interactions

It is recommended to monitor plasma levels when amlodipine is administered at the same time as any of these drugs.

  • Rifabutin.
  • Rifampin.
  • Carbamazepine
  • Phenobarbital (or primidone).
  • Phenytoin

They can reduce the bioavailability of amlodipine, so it may be necessary to increase the doses of amlodipine in patients who use these drugs.

Hawthorn or grapefruit should not be used when administering amlodipine.