Limited information is available on the acute toxicity of methocarbamol. Overdose of methocarbamol is frequently in conjunction with alcohol or other CNS depressants and includes the following symptoms: nausea, drowsiness, blurred vision, hypotension, seizures and coma.
One adult survived the deliberate ingestion of 22 to 30 grams of methocarbamol without serious toxicity. Another adult survived a dose of 30 to 50 grams. The principal symptom in both cases was extreme drowsiness. Treatment was symptomatic and recovery was uneventful. However, there have been cases of fatal overdose.
Management of overdose includes symptomatic and supportive treatment. Supportive measures include maintenance of an adequate airway, monitoring urinary output and vital signs, and administration of intravenous fluids if necessary.
The usefulness of haemodialysis in managing overdose is unknown.
Reports suggest overdose is more likely when methocarbamol is used alongside alcohol or other sedative drugs.
Signs of overdose include:
- severe drowsiness
- severe dizziness
- loss of consciousness
- difficulty breathing
- shaking on one side of the body