• Sedation and drowsiness are commonly reported adverse effects. Warn the person that drowsiness may affect the performance of skilled tasks (such as driving) and that baclofen may enhance the effects of alcohol.
• The Commission on Human Medicines (formerly Committee on Safety of Medicines) has advised that serious adverse effects (including psychosis, mania, paranoia, convulsions, tachycardia, and hyperthermia) can occur on abrupt withdrawal of baclofen [CSM, 1997]. A gradual reduction over 1–2 weeks is advised, or over a longer period if adverse effects occur during withdrawal.
• Consider using diazepam rather than baclofen in people with:
• Active (or history of) peptic ulceration, as baclofen stimulates gastric acid secretion.
• Psychiatric disorders, such as psychosis, schizophrenia, depression, or mania, as baclofen may exacerbate these conditions.
• Epilepsy, as baclofen may lower the seizure threshold; expert supervision is advised.
• Diabetes, as baclofen may increase blood glucose levels.
• Urinary retention, which may be exacerbated in people with a hypertonic bladder sphincter.
• Renal and hepatic impairment — the initial dose should be reduced in people with moderate-to-severe renal impairment, and titrated upwards according to the response. Liver function should be monitored in people with hepatic impairment.

[Sweetman, 2005; Twycross and Wilcock, 2007; BNF 56, 2008]