Sildenafil

What it is

Sildenafil is a PDE5 inhibitor. By blocking the enzyme that breaks down cyclic GMP, it lets the smooth muscle of penile arteries relax more fully in response to sexual stimulation, improving blood flow. It is used for erectile dysfunction, and works only alongside arousal.

Used for

• Erectile function

What to know while taking it

Absorption is fastest on an empty stomach, and a heavy or fatty meal delays onset, so it is usually kept apart from a large meal. Grapefruit and grapefruit juice slow its breakdown and raise blood levels. Because it also lowers blood pressure a little, combining it with an alpha-blocker such as tamsulosin or a calcium channel blocker such as amlodipine can add up to dizziness or faintness. It must never be combined with nitrates, including glyceryl trinitrate for chest pain, as the drop in blood pressure can be severe.

When to see a doctor

Chest pain during sex, fainting, sudden loss or blurring of vision or hearing, or an erection that will not subside are reasons to seek urgent medical care. Persistent headache, flushing or light-headedness should be raised with a doctor.

Worth knowing

• Never with nitrates
• Avoid grapefruit
• Absorbed better with fat