Erectile dysfunction (ED) is the persistent inability to attain and maintain an erection sufficient to permit satisfactory sexual performance. Prevalence estimates range from 19 to 52 per cent and increases with age.
ED is a presenting symptom of an underlying condition (see box, below) and is strongly associated with cardiovascular disease (CVD). Risk factors include smoking, lack of exercise, obesity and hyperlipidaemia. Regular exercise and weight loss may improve erectile function.
A detailed medical and psychosexual history should be taken to identify the cause of ED. Enquire about the nature of the onset, severity and duration of symptoms, the quality and duration of any erection and any problems with arousal, ejaculation and orgasm.
It is important to identify if there are emotional issues. Non-organic causes are associated with sudden onset of ED, premature loss of erection, better quality of waking or self-stimulated erections, ejaculatory problems, relationship issues or major life events.
Physical examination includes BP measurement and genital examination. Small testicular size and altered secondary sexual characteristics with loss of libido may indicate hypogonadism and examination of the penis may reveal Peyronie's disease. Rectal examination is vital in men over 50 to exclude prostatic enlargement or cancer.
A fasting glucose test is recommended for all patients and U&Es, creatinine, LFTs and TFTs should be taken if clinically indicated. If hypogonadism is suspected, a free testosterone or androgen index is recommended. When testosterone is low, luteinising hormone and prolactin levels should be checked.
A lipid profile is required if CVD is suspected and a haemoglobinopathy screen should be arranged for suspected sickle cell disease.
Testosterone deficiency from primary testicular failure or pituitary/hypothalamic disease (for example, prolactinoma) requires endocrinology referral. ED resulting from pelvic trauma or anatomical abnormality may respond well to surgery.
For younger patients with primary or longstanding ED, referral to a specialist with expertise in psychosexual health may be helpful.
Addressing reversible risk factors and encouraging lifestyle change will benefit general health and may improve erectile function.
Phosphodiesterase 5 (PDE5) inhibitors (sildenafil, tadalafil, vardenafil) are recommended as first-line therapy. With established safety profiles, these drugs are well tolerated and effective in the presence of adequate sexual stimulation. The usual starting dose is 50mg for sildenafil and 10mg for both tadalafil and vardenafil.
While these drugs are safe to use in stable cardiovascular disease, combination with nitrates may cause profound hypotension and is contraindicated. If chest pain develops, nitroglycerine must be withheld (24 hours after sildenafil/vardenafil, 48 hours after tadalafil).
Drug interactions occur with antihypertensives and alpha-blockers. Dosage of PDE5 inhibitors is reduced in severe kidney or hepatic dysfunction, and adjusted when prescribed alongside drugs affecting the cytochrome P450 enzyme pathway.
If the patient fails to respond to PDE5 inhibitors, titrate according to clinical response.
Advise the patient that the drug is only effective in maintaining the erection during sexual arousal.
In addition, food slows absorption and reduces efficacy of sildenafil and vardenafil, so these should not be taken with a meal. An adequate trial of PDE5 inhibitors is specified as six attempts at maximum dosage. Failing this, prescribe an alternative PDE5 inhibitor.
Apomorphine, a centrally acting dopamine agonist, is less effective than sildenafil. Taken sublingually, it enhances erectile function during sexual stimulation. It is safe and can be prescribed to patients taking nitrates.
An intracavernosal injection of alprostadil is second-line treatment. This is highly effective with a rapid onset of action, however long-term compliance is poor. Side-effects include pain, prolonged erections, priapism, fibrosis and mild hypotension. Bleeding disorders and anticoagulant therapy are contraindications to use.
Erections lasting more than four hours require urgent intervention to prevent permanent damage to the intracavernous muscle and subsequent treatment doses should be reduced.
An alprostadil intraurethral pellet is less effective. A penile constriction ring may improve efficacy. Side-effects include local pain and bleeding, dizziness, UTI, penile fibrosis and priapism. Men with pregnant partners should use barrier contraception.
Vacuum constriction devices used with a constrictor ring at the base of the penis induce erection by passive engorgement. The ring should be removed within 30 minutes to avoid skin necrosis. Although highly effective, long-term compliance is poor. Side-effects include pain, bruising and numbness.
Vacuum constriction devices are contraindicated in bleeding disorders or anticoagulant therapy. This method may suit patients with a supportive partner and infrequent intercourse.
Implanted penile prostheses are a third-line treatment and highly effective. Complications of mechanical failure and infection occur infrequently.
Education, counselling and shared decision-making are key to the success of treatment. Guidelines recommend involving patients' partners in this process, whose support and engagement are vital.
|Causes of erectile dysfunction|
- Dr Duckworth is a salaried GP in Cornwall
1. European Association of Urology. Guidelines on male sexual dysfunction: erectile dysfunction and premature ejaculation 2010.
2. Johannes CB, Araujo AB, Feldman HA, et al. J Urol 2000; 163(2): 460-3.
3. Ralph D, McNicholas T. BMJ 2000; 321: 499-503.
4. Jang DJ, Lee MS, Shin BC, et al. Br J Clin Pharmacol 2008; 66(4): 444-50.