Description
Uses and Administration of Losartan in Kenya
Losartan is an angiotensin II receptor antagonist with antihypertensive activity due mainly to selective blockade of AT1 receptors and the consequent reduced pressor effect of angiotensin II. It is used in the management of hypertension, particularly in patients who develop cough with other Angiotensin-Converting Enzyme inhibitors and to reduce the risk of stroke in patients with left ventricular hypertrophy, and in the treatment of diabetic nephropathy in Kenya. It has also been tried in heart failure and in myocardial infarction.
Losartan is given by mouth as the potassium salt. The maximum hypotensive effect is achieved in about 3 to 6 weeks after initiating treatment.
In hypertension the usual dose applied in most Kenyan hypertensive patients is 50 mg once daily. The dose may be increased, if necessary, to 100 mg daily as a single dose or in two divided doses. An initial dose of 25 mg once daily should be given to patients with intravascular fluid depletion, and is recommended in Kenya in the elderly over 75 years of age. Similar reductions may be appropriate in patients with hepatic or renal impairment.
Children aged 6 years or over with hypertension may be given an initial dose of 700 micrograms/kg once daily, with a maximum of 50 mg, adjusted according to response; doses higher than 1.4 mg/kg or 100 mg daily have not been studied and should be tried only at the hospital with careful monitoring.
In diabetic nephropathy losartan is given in an initial dose of 50 mg once daily, increased to 100 mg once daily depending on the blood pressure.
Adverse Effects and Side Effects of Losartan Antihypertensive Drug in Kenya
Adverse effects of losartan have been reported to be usually mild and transient, and include dizziness, headache, and dose-related orthostatic hypotension. Hypotension may occur particularly in patients with volume depletion (for example those who have received high-dose diuretics). Impaired renal function and, rarely, rash, urticaria, pruritus, angioedema, and raised liver enzyme values may occur. Hyperkalaemia, myalgia, and arthralgia have been reported. Losartan appears less likely than ACE inhibitors to cause cough. Other adverse effects that have been reported with angiotensin II receptor antagonists include respiratory-tract disorders, back pain, gastrointestinal disturbances, fatigue, and neutropenia.
Precautions
Losartan is contra-indicated/should not be used or tried in pregnancy. Losartan is contra-indicated in pregnancy since it has been associated with fetal toxicity in animal studies and other drugs that act on the renin-angiotensin system, such as ACE inhibitors, have been associated with fetal toxicity in humans. Oligohydramnios with subsequent fetal death occurred in a patient who received losartan during weeks 20 to 31 of pregnancy; the effects on the fetus were similar to those reported with other blood pressure drugs similar to Losartan. A number of similar cases have subsequently been reported with losartan, candesartan, and valsartan. It should be used with caution in patients with renal artery stenosis. Losartan is excreted in urine and in bile and reduced doses may therefore be required in patients with renal impairment and should be considered in patients with hepatic impairment. Patients with volume depletion in Kenya (for example those who have received high-dose diuretic therapy) may experience hypotension; volume depletion should be corrected before starting therapy, or a low initial dose should be used. Since hyperkalaemia may occur, serum-potassium concentrations should be monitored, especially in the elderly and patients with renal impairment, and the concomitant use of potassium-sparing diuretics should generally be avoided.
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