Herbal medicine causing likely strychnine poisoning

Abstract

`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.