Alpha-adrenoceptor blockers are used in benign prostatic hyperplasia (BPH) to reduce bladder outflow obstruction by relaxing smooth muscle. They do not reduce the size of the prostate.
Drug regimens The alpha-adrenoceptor blockers include alfuzosin, doxazosin, indoramin, prazosin, tamsulosin and terazosin. They relieve symptoms by selectively blocking peripheral alpha1-adrenoreceptors, producing vasodilator and smooth muscle relaxant effects.
Tamsulosin is the most selective drug and the most widely prescribed for BPH. Its elimination half-life is around 10 hours allowing for once daily dosing. It requires no dose titration and is given at a dose of 0.4mg once daily.
Alfuzosin Initially 2.5mg three times daily, maximum 10mg daily (elderly initially 2.5mg twice daily). The drug is also available as a modified release, 10mg once daily XL formulation.
Doxazosin Initially 1mg daily. May be doubled at one to two week intervals to usual maintenance doses between 2-4mg daily. Maximum 8mg daily.
Indoramin Initially 20mg twice daily, maximum 100mg daily in divided doses.
Prazosin Initially 0.5mg twice daily for three to seven days to a maximum 2mg twice daily.
Terazosin Initially 1mg at night, doubled at one to two week intervals to usual maintenance 5-10mg daily.
Patient’s knowledge of the medicine’s use
Alpha-adrenoceptor blocking drugs provide relief from the lower urinary tract symptoms of BPH and improve urinary outflow, but have no effect on prostate size.
Is the medication working?
Treatment produces symptomatic relief but the drugs can take four to six weeks to be effective.
Side effects
Hypotension, drowsiness, dizziness, headaches, asthenia and syncope. Tamsulosin is well tolerated, which is one of the reasons to support its reclassification to a P medicine.
Patients starting on alfuzosin, prazosin and terazosin may experience a hypotensive effect with the first dose so should be warned to lie down until symptoms of fatigue, dizziness or sweating resolve.
Monitoring and lifestyle
Patients should be advised to regulate fluid intake to reduce symptoms, particularly before going to bed or going out. Drinks containing alcohol or caffeine should be avoided.
Patients with undiagnosed BPH presenting with the common symptoms may be suitable for short-term treatment with P tamsulosin providing they have no contra-indications (see below). The pharmacist can make an initial two-week supply and advise the patient to return to the pharmacy in 14 days. If symptoms have improved and no side effects have developed a further 28 days’ supply can be made. After six weeks the patient needs to see a GP who will confirm if the pharmacy supply is appropriate to continue. Patients on P tamsulosin will need an annual review with their GP.
Contra-indications for P tamsulosin include: • Age less than 45 years. • On medications for BPH. • Due for cataract surgery. • Taking alpha1 blockers for the treatment of hypertension. • Symptoms suggestive of UTI (fever etc). • Haematuria or painful urination. • Cardiovascular, hepatic or renal disease. • History of orthostatic hypotension, heart, liver or kidney disease. • History of prostate surgery.
Andrew Sturrock is a hospital pharmacist in Gateshead.
