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Sildenafil in clinical practice

Clinical bottom line

A large retrospective survey of sildenafil in clinical practice confirms results of clinical trials, with no evidence of rare but serious adverse events.


Reference

A Boshier et al. Evaluation of the safety of sildenafil for male erectile dysfunction: experience gained in general practice use in England in 1999. BJU International 2004 93:796-801.

Background

Sildenafil became available in the UK in 1998 for the treatment of erectile dysfunction, a condition most commonly found in older men. At the time there were concerns over possible cardiac effect, and use with men with nitrates was contraindicated.

Study

This was a prescription event monitoring study in which exposure data were derived from dispensed prescription details and outcome data from questionnaires returned by GPs. The period was April to August 1999, with questionnaires sent to GPs about 18 months after the date of the first dispensed prescription.

Questionnaires sought information about demographics, dose of sildenafil, reasons for discontinuation if it was stopped, and information about suspected adverse drug reactions. Events would include any new diagnosis, referral to a consultant, or admission to hospital, deterioration or improvement in current illness, alteration in laboratory values, or other complaint of sufficient importance to enter into the patient's notes.

Results

The number of questionnaires posted was 45,000, and 25,000 (55%) were returned, with useful information on 22,500. The men referred to in these forms the median age was 60 years, with a range of 18 to 92 years. Diabetes was a factor in at least 18% of these men. Sildenafil was reported as effective in 71%.

There were 145 events coded as adverse drug reactions the GPs thought attributable to sildenafil (Table 1). These were mainly headache, flushing and dyspepsia. Others included myalgia, priapism, and oedema. There were three cases of palpitations, two of tachycardia, and one each of angina, myocardial infarction, and stroke.

Table 1: Main ADRs with sildenafil

ADR
Number
Headache
30
Unspecified
22
Flushing
16
Dyspepsia
13
Dizziness
7
Visual disturbance
7

 

Just under 4000 men stopped taking sildenafil (18%), mostly because of lack of efficacy, though also because the condition had improved, and because of adverse events or medical conditions.

The leading causes of death were malignancy (122), myocardial infarction (56), and ischaemic heart disease (20). The standardised mortality rate was lower than that for men in England in 1998, but with wide confidence intervals.

Comment

The large and detailed retrospective survey of 22,000 men prescribed sildenafil largely confirms results from the clinical trials. Success in about 70% or so, with some adverse events, but no evidence of rare, serious adverse events.