Betahistine

What it is

Betahistine is a histamine analogue that acts weakly at H1 receptors and as an antagonist at H3 receptors. The effect is thought to improve microcirculation in the inner ear and to modulate vestibular signalling, which reduces the vertigo attacks it is prescribed for. It is used for dizziness of vestibular origin.

Used for

• Dizziness

What to know while taking it

It is taken with food, which softens the stomach upset that is its most common complaint. Because it is a histamine analogue it can provoke bronchospasm, so asthma calls for caution and any worsening of breathing or wheeze should be reported. The same histamine action increases gastric acid, which is why a current or past peptic ulcer is a reason for caution and why stomach pain during treatment should not simply be ignored. Benefit builds over weeks rather than after a single dose.

When to see a doctor

Wheezing, chest tightness or worsening shortness of breath, and stomach pain, black stools or vomiting that looks like coffee grounds, all mean see a doctor. New or worsening vertigo with hearing loss, headache, weakness or difficulty speaking should be assessed promptly.

Worth knowing

• Use with caution in asthma
• Caution with peptic ulcer