Herbal medicine causing likely strychnine poisoning.

'Maqianzi' (the dried ripe seed of Strychnos nux-vomica L.) contains 1.0-1.4% each of strychnine and brucine. After processing to reduce its toxicity, 'maqianzi' was used as a herbal remedy for rheumatism, musculoskeletal injuries and limb paralysis. A 42-year old woman with neck pain was prescribed 15 g of 'maqianzi' to be taken in two doses at 7 hours apart, although the recommended dose was 0.3-0.6 g. She was apparently well after drinking the first of two bowls of 'maqianzi' decoction. One hour after she drank the second bowl of herbal decoction, she suddenly developed tonic contractions of all her limb muscles and carpopedal spasm lasting 5 min, difficulty in breathing, chest discomfort and perioral numbness. The second bowl of decoction probably became more concentrated because of evaporation of water during continued boiling and contained a larger amount of 'maqianzi'. On arrival in the hospital 1 hour later, she complained of muscle pain and tiredness. She was found to have hyperventilation and weakness of four limbs, with muscle power of grade 5(-)/5. All her symptoms gradually subsided over the next few hours. This case illustrated that 'maqianzi' can cause strychnine poisoning even after processing, especially when the recommended dose is greatly exceeded. In any patient with 'unexplained' muscle spasms or convulsions, strychnine poisoning should be included in the differential diagnosis and they should be asked about the use of herbal medicines.