Opisthorchis viverrini: clinical experience with praziquantel in Hospital for Tropical Diseases.

Praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]++ +isoquinolin- 4-one, EMBAY 8440, Biltricide) has been used in 4853 patients with Opisthorchis viverrini infection. 786 patients were treated as inpatients with extensive clinical evaluation and the rest were out-patients. A cure rate (evaluated with 5 faecal samples) of 100% was obtained in groups given 6 X 25 mg/kg on 2 days and 3 X 25 mg/kg on 1 day, while in groups given 2 X 25 mg/kg, 1 X 25 mg/kg and 1 X 40 mg/kg all on 1 day the cure rates were 88, 44 and 91%, respectively. With one sample evaluation the parasitological cure rate was 96% in further 96 patients excreting the geometric mean (GM) of 5394 eggs per gram (EPG) and receiving 1 X 40 mg/kg. Another 68 patients with an egg output of 26044 (GM/EPG) and treated with 1 X 50 mg/kg showed a cure rate of 97% by similar evaluation. Side effects were mild and transient and were more frequent in higher dosage groups. They included anorexia, nausea, vomiting, abdominal pain, epigastric pain, rumbling in the abdomen, diarrhoea, lassitude, myalgia, headache, dizziness, sleeplessness, sleepiness, "hot sensation", shortness of breath, and skin rash in a few cases. Headache (30.7%) was most common in the 6 X 25 mg/kg group. In 53 patients with severe jaundice the side effects were similar. There was no evidence of toxicity. Remarkable was one patient treated with 1 X 50 mg/kg who expelled 5636 O. viverrini worms, most of which were elongated and damaged. When a single dose is prescribed it should be given at bed time to reduce the side effect of sedation.