Login

Phosphodiesterase 5 (PDE5) Inhibitors

Action: These drugs potentiate the action of Nitric Oxide (NO), producing cavernosal smooth muscle relaxation and penile erection. They are only a treatment for loss of erections and in studies has been shown to have no effect on libido or sexual desire.

Efficacy: PDE5 Inhibitors are effective in restoring natural erectile function in patients with ED of psychogenic, organic and mixed causes. In men with diabetes, studies have shown an efficacy rate of 56%.

Drugs and doses:

Sildenafil

• Starting dose 50mg , reduce dose in elderly to 25mg
• Titrate dose up to a maximum of 100mg

Vardenafil

• Starting dose 10mg, 5mg in elderly
• Titrate dose up to a maximum of 20mg

Sildenafil and Vardenafil have the same duration of effect, which is about 4-5hrs.

Tadalafil

• Starting dose 10mg
• Maximum dose 20mg

Tadalafil is a longer acting PDE5 inhibitor and its effect may last 24-48hrs. It therefore sometimes dissociates taking a pill with sex, which may be important to some men. Head to head studies of efficacy are awaited.

For all drugs: see BNF for further information

• Higher doses are associated with an increased incidence of side effects.
• Instruct patient to take a tablet approximately 1 hour prior to anticipated sexual activity.
• Worth trying for up to eight separate occasions at maximum dose, over a period of time chosen by the patient, before dismissing as ineffective.

Adverse Effects: All side effects appear more frequently with increased doses

• Headache is commonest.
• Other vasculogenic effects e.g. flushing and dizziness occur occasionally.
• Dyspepsia (in up to 5%).
• Proximal myalgia.
• Nasal congestion.

Drug Interactions:

• PDE5 inhibitors can potentiate the action of nitrates therefore in patients who take nitrates of any type, including sublingual GTN or oral Nicorandil, concurrent use of any PDE5
• inhibitor is contra-indicated.

Cautions:

• Cardiovascular disease.
• Anatomical deformity of penis (e.g. Peyronies disease).
• Predisposition to prolonged erection (e.g. leukaemia, multiple myeloma).
• Hepatic impairment.
• Renal impairment.

Contra-indications:

• Concomitant Nitrate (including buccal or sublingual) or Nicorandil therapy.
• Conditions in which sexual activity is inadvisable.
• Recent stroke/Myocardial infarction within 3 months.
• Hypotension (BP less than 90/50mmHg).
• Severe hepatic dysfunction.
• Hereditary degenerative retinal disorders.
• Concomitant treatment for ED (except counselling).

Centrally Acting Drugs

Prescribing Restrictions:

• In most cases, GPs are limited in their use of NHS prescriptions for the drug treatment of ED. However this restriction does not apply to men with diabetes.
• Community pharmacists are unable to dispense NHS prescriptions that do not contain the endorsement 'SLS'.
• The dept of Health suggests that one treatment per week is appropriate.
• If the GP considers that more than one treatment per week is reasonable, then this may be prescribed on the NHS.

©2010All Rights Reserved