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In the UK the currently available phosphodiesterase (PDE5) inhibitors are sildenafil
Viagra), tadalafil (Cialis) and vardenafil (Levitra)
mechanism of action:
inhibitors prevent the degradation of cyclic GMP thereby prolonging production
of the vasodilator nitric oxide. PDE5 inhibitors are only effective in the context
of sexual arousal
dosing of PDE5 inhibitors:
- doses may
need to be titrated to achieve effect
- the majority of diabetics need the
maximum dose of PDE5 inhibitor to achieve effect (1)
- PDE5 inhibitors
may take several doses over time to work. The patient should be warned that he
may need 8 attempts before a satisfactory erection occurs – at least 4 at the
highest dose (1)
- these occur
secondary to smooth muscle relaxation and include headache, flushing and acid
reflux but are not usually limiting
- transient blue vision can occur with
use of sildenafil
The respective summary of products must be consulted
before prescribing any of the drugs mentioned.
Heart Foundation (factfile 6/2005).Drugs and Erectile Dysfunction.
(2003), 14 (20), 28-31.
Last reviewed 01/2018