Methylphenidate Intoxication: Somnolence as an Uncommon Clinical Symptom and Proof of Overdosing by Increased Serum Levels of Ritalinic Acid

Abstract

There is considerable evidence for an increase of methylphenidate (MPH) abuse; thus, physicians might be confronted more frequently with MPH intoxications. Possible symptoms of intoxications with MPH are orofacial, stereotypic movements and tics as well as tachycardia, cardiac arrhythmias, arterial hypertension, hyperthermia, hallucinations and epileptic seizures. Here we report a patient who demonstrated somnolence as an uncommon clinical feature of MPH intoxication. The patient exhibited subnormal MPH serum levels (3 μg/l), however markedly increased serum levels of ritalinic acid (821 μg/l; inactive metabolite of MPH), that finally confirmed the initially suspected MPH intoxication. Due to the short half-life of orally administered MPH (t_1/2~3 h) the sole measurement of MPH serum levels might be misleading concerning the proof of MPH overdosing in some cases. Parallel measurement of MPH and ritalinic acid is recommended in cases with suspected MPH intoxication and insufficient anamnestic data.

Key words

abuse - ADHS - neuroenhancement - stimulants - toxicology

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