The side effects of hyoscine butylbromide include dryness of the mouth with difficulty in swallowing, thirst, dilatation of the pupils with loss of accommodation and photophobia, increased intra-ocular pressures, flushing and dryness of the skin, transient bradycardia followed by tachycardia, with palpitations and arrhythmias, and desire to urinate with the inability to do so, as well as reduction in the tone and motility of the gastrointestinal tract leading to constipation. Occasionally vomiting, giddiness and staggering may occur.