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.
Hytrin (Abbott Australasia)
1 mg, 2 mg, 5 mg and 10 mg tablets
Indication: hypertension, benign prostatic hypertrophy
Terazosin is an alpha1 adrenergic receptor antagonist with a structure similar to prazosin. It lowers blood pressure by decreasing vascular resistance and can relieve the symptoms of benign prostatic hypertrophy by reducing the smooth muscle tone of the bladder outlet.
For both indications, treatment should begin with a low dose and be increased according to the response. Giving the dose at bedtime also helps to reduce the risks of hypotension and syncope.
Terazosin is rapidly absorbed from the gut. Its effects begin within 15 minutes and can last for up to 24 hours so only one dose per day is needed. The drug is mainly metabolised and has a half life of 12 hours.
For benign prostatic hypertrophy, the maximum benefit occurs after 3-6 months of treatment. While terazosin improves urinary flow rates significantly more than placebo, the clinical improvement may be modest. If there has been no response after 6 months, continuing treatment has no advantage.
In hypertension, the company recommends that the blood pressure is checked at the end of a dose interval. If the blood pressure has not been controlled by a single daily dose, the dose can be increased or the drug may be given twice a day. There is probably no benefit in giving higher doses to patients who are not controlled on 20 mg per day.
The adverse reactions profile varies slightly between the treatment groups. Patients taking terazosin for prostatic symptoms are more likely to develop postural hypotension, while hypertensive patients are more likely to experience palpitations and peripheral oedema. Common adverse effects associated with each indication include headache, dizziness and asthenia.