Acute amitriptyline withdrawal and hyponatraemia. A case report

The tricyclic antidepressants (TCAs) are commonly used in the treatment of depression and, perhaps due to the nature of the condition being treated, figure prominently in cases of deliberate overdosage, where the toxicity of amitriptyline has been well established. However, the abrupt cessation of TCA administration can also be detrimental to the patient, triggering withdrawal phenomena often characterised by an exacerbation of the symptoms for which the patient was originally treated. We present a biochemically proven case of amitriptyline withdrawal where the clinical features at presentation made it difficult to distinguish from acute toxicity. The patient's neurological signs and distended bladder suggested amitriptyline toxicity, whereas the history and signs of cholinergic hyperactivity were consistent with acute withdrawal. The diagnosis was confirmed at a later date when further history and a biochemical analysis of plasma TCA concentrations became available. Hyponatraemia may have exacerbated the condition of the patient, whether or not it was caused by amitriptyline.