Benign prostatic hyperplasia (BPH) is a common condition that increases in prevalence with age. The enlarged prostate compresses the urethra and produces bladder outflow obstruction and lower urinary tract symptoms.
The two main drug options for treatment are alpha-adrenoceptor blocking drugs, which relax smooth muscle, and 5-alpha-reductase inhibitors, which can reduce prostate size.
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 for alpha-1a receptors and the most widely prescribed for BPH. Its elimination half-life is around 10 hours allowing 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). Alfuzosin 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 dose between 2-4mg daily. Maximum 8mg daily.
Indoramin 20mg twice daily, maximum 100mg daily in divided doses.
Prazosin Initially 0.5mg twice daily for three to seven days to maximum 2mg twice daily.
Terazosin Initially 1mg at night, doubled at one to two week intervals to usual maintenance dose 5-10mg daily.
The 5-alpha-reductase inhibitors are dutasteride and finasteride; they inhibit the enzyme (5-alpha-reductase), which is responsible for converting testosterone to dihydrotestosterone (DHT) in the prostate. DHT is the hormone responsible for prostatic growth.
Dutasteride 500micrograms daily.
Finasteride 5mg daily. (A 1mg formulation is also licensed to treat male pattern baldness).
Patient’s knowledge of the medicine’s use
Alpha-adrenoceptor blocking drugs improve urinary outflow and relieve symptoms of BPH but have no effect on prostate size.
5-alpha-reductase inhibitors reduce prostate size, improving urinary flow rates and symptoms of BPH. They are most effective in patients with large prostates but can be less effective at reducing symptoms than the alpha-adrenoceptor blockers.
Is the medication working?
Treatment with alpha-adrenoceptor blockers produces symptomatic relief but benefits are not immediate. The drugs can take four to six weeks to become effective.
5-alpha-reductase inhibitors generally take longer to provide symptomatic relief, improving symptoms over several months.
Side effects
The alpha-adrenoceptor blockers can cause hypotension, drowsiness, dizziness, headaches, asthenia and syncope. Tamsulosin is well tolerated, which is one of the reasons supporting 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 such as fatigue, dizziness or sweating resolve.
The side effects of 5-alpha-reductase inhibitors include decreased libido, impotence, reduced ejaculatory volume and reversal of male pattern baldness. Patients should be informed about the potential side effects, especially sexual dysfunction, when discussing the treatment options available.
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.
Pregnant women should not handle finasteride and dutasteride. Both drugs are excreted in semen so use of a condom is recommended if the partner is pregnant. Sexual partners of child-bearing age should be referred to a GP to discuss appropriate methods of contraception.
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 under MUR tips for alpha-adrenoceptor blockers). The pharmacist can make an initial two-week supply and the patient advised 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.
Andrew Sturrock is a hospital pharmacist in Gateshead.
