The following adverse reactions have been experienced with the as follows indicated frequencies in betahistine-treated patients in placebo-controlled clinical trials [very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1,000 to <1/100); rare (≥1/10,000 to <1/1,000); very rare (<1/10,000)].
Gastrointestinal disorders: Common: nausea and dyspepsia.
Nervous system disorders: Common: headache.
In addition to those events reported during clinical trials, the following adverse reactions have been reported spontaneously during post-marketing use and in scientific literature. A frequency cannot be estimated from the available data and is therefore classified as "not known".
Immune System disorders: Hypersensitivity reactions, e.g. anaphylaxis.
Gastrointestinal disorders: Mild gastric complaints (e.g. vomiting, gastrointestinal pain, abdominal distension and bloating). These can normally be dealt with by taking the dose during meals or by lowering the dose.
Skin and subcutaneous tissue disorders: Cutaneous and subcutaneous hypersensitivity reactions, in particular angioneurotic edema, urticaria, rash, and pruritus.