Medicines and Drugs to Treat High Blood Pressure

Methyldopa (Aldomet)

In the body, methyldopa is broken down to its metabolite (alpha-methylnorepinephrine) which acts on the areas of the brain known to cause vasodilatation. Besides this central action, a peripheral anti-hypertensive action is also possible. It is considered to be the drug of choice for pregnancy associated hypertension.

Dosage: Methyldopa is administered orally in a dose of 250 mg, 3 to 4 times daily.

Adverse Effects: Methyldopa causes sedation and drowsiness in almost all cases, however it disappears after a few days of therapy. Other adverse effects are quite rare: they include dryness of the mouth, nasal congestion, impotence, retention of fluids, drug allergy, and depression. It may cause impairment of liver functions, which however return to normal when the drug is stopped. In rare circumstances it may cause anaemia (haemolytic anaemia) and depression of the bone marrow.

Clonidine (Arkamin)

It causes lowering of the heart rate and dilatation of blood vessels by its action on certain areas of the brain like the medulla and hypothalamus which are known to control the blood pressure. Its effects are enhanced by diuretics.

Dosage: Clonidine is administered orally in a dose range of 50 ug to 200 ug in 2 to 3 divided parts in conjunction with hydrochlorothiazide, in case of mild to moderate hypertension.

Adverse Effects: It causes drowsiness and dryness of the mouth which may persist as long as the treatment is continued. Constipation and impotence may occur in 10 to 20 per cent cases on prolonged Use. Allergic reactions including skin rash and itching are not so serious. If the drug is suddenly stopped, restlessness, chills, nausea, sweating, and insomnia with a sharp rise in the blood pressure may occur. However, its use is declining.

Angiotensin- Converting Enzyme (ACE) inhibitors

Captopril (Aceten, Angiopril, Captopril), Enalapril (Enam, Enace), Lisinopril (Cipril, Hipril), Ramipril (Ramace), Perindopril (Coversyl)

These drugs reduce the blood pressure by preventing the production of angiotensin-II which blood vessels in the body.

The anti-hypertensive effect is related to vasodilatation (decreased total peripheral resistance). The blood pressure falls within two hours, but several weeks are required for achieving maximum therapeutic response. Diuretics enhance the anti-hypertensive effects. Currently these drugs are the most commonly used in diabetes associated with hypertension.

Captopril (Aceten, Angiopril, Captopril)

Captopril is used in a dose of 12.5 mg, twice or thrice daily. It can be increased to 25 to 50 mg three times daily.

Adverse Effects: About 10 per cent patients develop skin rashes with this drug. Loss disturbance of taste occurs in about 70 per cent patients. Gastro-intestinal symptoms like nausea, vomiting, abdominal pain, flatulence, and diarrhoea may occur. It may cause loss of protein in the urine in 2 per cent patients and affect the kidneys adversely. Anti-arthritis drugs like indomethacin and aspirin antagonize the anti-hypertensive effect of captopril. A dry hacking cough is troublesome side effect, occurring in about 30 per cent cases and may require change of drug.

Enalapril (Enam, Enace, Nuril 5 mg, 10 mg)

This is activated in body to have antihypertensive effect. Food does not affect its absorption. It is more potent than captopril and less likely to produce precipitous hypotension and taste disturbance.

Usual dose is 2.5 mg per day in elderly and 5 mg per day in patients less than 60 years of age. Dose increment is done weekly to a maximum dose of 10 to 20 mg in two divided doses. It can be combined with a diuretic. It can cause dry cough and skin rash but less frequently than captopril.

Lisinopril (Listril Lisinace 5 mg, 10 mg tablet)

A longer acting drug used in a dose of 5 to 10 mg once a day. Like enalapril it is less likely to cause adverse effects.

Ramipril (Ramace 1.25 mg, 2.5 mg, 5 mg tablet)

This agent inhibits tissue ACE and it prolongs survival in chronic heart failure. It has brain protective action when used in stroke and heart protective effect when used after heart attack.

Beneficial Effects of ACE-inhibitors: A number of benefits accrue from their use. These are:

Smooth reduction of BP in all cases of high blood pressure.

Protective effect on heart (preserves heart muscle structure and function) resulting better output. Prevention of vascular damage.

Preservation of kidney function in diabetics.

Improvement in the quality of life.

Improvement in function of vascular inner coat (endothelium).

Ramipril is shown to decrease cardiovascular deaths by 25 per cent, stroke by 31 per cent and heart attacks by 20 per cent.

No derangement of sexual function.

Precautions

Captopril and enalapril cause rapid fall in the blood pressure and may precipitate a fainting attack.

These should be used cautiously in patients with coronary artery disease.

Kidney function should be checked frequently with these drugs. The dose should be reduced in patients with impaired kidney function.

These should never be used during pregnancy; they cause foetal growth retardation.

Angiotensin Receptor Blockers

This group of drugs are suitable for those who cannot tolerate ACE inhibitors. Antihypertensive effects are similar to those of ACE-Is. The drugs of this class are:

Losartan (Losacor, Tozaart 25 mg, 50 mg tablet): Its usual dose is 50 mg initially ( ge 25 to 100 mg) in a day. Lower dose is needed in liver and kidney disease. It usually does not cause cough as seen with ACE-Is.

A fixed dose combination with diuretic (TOZAAR-H), ramipril, amlodipine, atenolol and lisinopril is also available.

Candesartan (Cantar, Candesar 4 mg, 8 mg, 16 mg tablet): Its usual dose is 2 to 4 mg, once a day and maximum dose is 16 mg per day.

Irbesartan (Irovel 150 mg, 300 mg tablet): It is usually given in a dose of 150 mg once a day (maximum 300 mg per day).

Telmisartan: Its usual dose is one tablet once a day.

These agents are increasingly used in hypertension to prevent damage to heart and kidneys.