Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.


Micardis (Boehringer Ingelheim)
Pritor (Glaxo Wellcome)
40 mg and 80 mg tablets
Approved indication: hypertension
Australian Medicines Handbook Section 6.4.5

Telmisartan adds to the choice of angiotensin receptor antagonists1 available in Australia. It is suitable for patients with mild to moderate hypertension who cannot tolerate other treatments.

Patients take telmisartan once a day. There is extensive first-pass metabolism so the bioavailability of a 40 mg dose is 40%. Less than 1% of the dose is excreted unchanged in the urine. The half-life is approximately 20 hours.

Blockade of the AT1 receptor reduces vascular resistance. This lowers the blood pressure, but it does not increase the pulse. The effect on blood pressure is slow and the full effect is not reached for 4-8 weeks. Orthostatic hypotension is uncommon.

Telmisartan has been compared with other antihypertensive drugs and placebo. In a comparison with enalapril, 278 elderly patients were treated for 26 weeks. Both drugs provided effective 24-hour control of blood pressure. The mean reductions in blood pressures were 22/12 for telmisartan and 20/11 for enalapril.2 An unpublished trial compared telmisartan and losartan. Although the treatment period was only six weeks, telmisartan had a greater effect on blood pressure. The mean reductions were 11/7 for telmisartan and 6/4 for losartan.

Telmisartan is generally well tolerated. In clinical trials the incidence of cough was approximately 1%. Diarrhoea and dyspepsia occur more frequently than with placebo.

Gastrointestinal adverse effects are more common in patients with a history of gastrointestinal problems.

In clinical trials patients have been treated with telmisartan and hydrochlorothiazide without causing significant problems. There is, however, an interaction with digoxin so digoxin concentrations should be checked when starting or changing the dose of telmisartan.

References

  1. Johnston CI. Angiotensin receptor antagonists for the treatment of hypertension. Aust Prescr 1998;21:95-7.
  2. Karlberg BE, Lins LE, Hermansson K. Efficacy and safety of telmisartan, a selective AT1 receptor antagonist, compared with enalapril in elderly patients with primary hypertension. J Hypertens 1999;17:293-302.