Treatment of Opisthorchis viverrini and intestinal fluke infections with Praziquantel.

The study was carried out from September to November 1997 in Phrae Province of northern Thailand. A total of 95 adult patients with Opisthorchis-like ova in their stools were randomly treated with two different manufactured Praziquantels. Group 1, consisting of 49 patients, received a single dose of 40 mg per kg Praziquantel manufactured by the Thai Government Pharmaceutical Organization. Group 2 (46 patients) received Biltricide at the same dosage. Haplorchis taichui, H. yokogawai, Echinostome spp., O. viverrini, Taenia saginata and Enterobius vermicularis were expelled in the stools after treatment. Minute intestinal flukes were detected in 64% of patients. O. viverrini was found in lower proportion of 17%. By formalin-ether concentration examination one stool specimen from each patient, the cure rate in both groups on the 30th day of treatment was 100%. The side effects of the two different Praziquantel treatments were mild with no significant difference. Praziquantel, regardless of its manufacture, proved effective against O. viverrini and other minute intestinal flukes (H. taichui, H. yokogawai and Echinostome spp).

Drug treatment of neurocysticercosis.

Neurocysticercosis, the most common parasitic disease of the central nervous system, was treated surgically for a long time. Praziquantel (an isoquinolone) and albendazole (an imidazole) are anticysticercal drugs that are currently being used for the treatment of neurocysticercosis. Both have been reported to eliminate or markedly reduce the number and size of cysticerci. Albendazole is less expensive than praziquantel, and is as effective when given for 8 days as compared to longer periods. In a small number of comparative trials, albendazole appeared to be slightly more effective than praziquantel for the treatment of parenchymal cysticercosis. Albendazole has also been found effective in ventricular, subarachnoidal and racemose forms of the disease. However, the response to treatment is not universal. Treatment with these drugs has been associated with a high frequency of adverse reactions, probably due to the host's inflammatory reaction to the dying parasites. Headache, nausea and seizures are common but usually transient. Steroids appear to ameliorate these effects and their concomitant administration has been advocated. However, no data are available to support this view. The rationale of medical therapy in spinal cysticercosis is presently based on the reported efficacy of anticysticercal drugs in cerebral cysticercosis. A marked improvement in an associated seizure disorder following anticysticercal therapy has been observed. Though seizure control is better, the total duration of anti-epileptic drug therapy has not been determined. Some single enhancing computed tomography lesions in patients of epilepsy may be benign forms of neurocysticercosis. The spontaneous resolution of a majority of these lesions has led to doubts of them being merely infective in aetiology. Also, a controlled trial could not demonstrate any beneficial effect of albendazole on such lesions. Hence, most authors recommend that these patients should be treated with anti-epileptic drugs only. Doubts persist about the efficacy of anticysticercal drugs in altering the natural course of the disease and the reported tendency of cysticercus lesions to resolve.

Opisthorchis viverrini: effect of praziquantel on the adult tegument.

Ultrastructural changes of the tegument of adult liver flukes, Opisthorchis viverrini, after in vitro incubation in Minimal Essential Medium containing 0, 0.1, 1.0 and 10.0 micrograms/ml of anthelminthic praziquantel for 5, 15, 30, 45 and 60 minutes were investigated by scanning (SEM) and transmission (TEM) electron microscopy. SEM observations showed that the surface damage was composed of blebbing due to the swelling of microvilli, followed later by the disruption of these structures to form lesions that caused the erosion and desquamation of the surface. Sensory papillae, by contrast, appeared relatively unaffected. The surface changes could be observed at all doses but the extent of damage increased with increasing duration of incubation and concentration of the drug. The ventral as well as the dorsal surfaces exhibited similar change, whereas the anterior part tended to be damaged less than the posterior part. Under TEM observations, the earliest sign of changes was the depolymerization of the microtrabecular network in scattered foci, which resulted in the formation of non-membrane-bound vacuoles under microvilli. The basal infoldings also became dilated, and some turned into membrane-bound vacuoles in the basal zone. Subsequently, microvilli became enlarged, and eventually formed blebs that later rupture to form lesion spots as observed in the SEM. Finally, the microtrabecular network in all regions broke down, creating vacuoles of various sizes throughout the tegument, leading to its total disintegration and detachment. The sequence of morphological changes was generally similar at all doses; however, the changes occurred faster at the higher doses and the longer incubation times. In addition, at the longer durations myofilaments in most muscle cells also became depolymerized, while microtubules were unchanged by the drug. Therefore, it is possible that praziquantel, through its induction of Ca2+ influx, causes depolymerization of the microtrabecular network that leads to the vacuolization, swelling, blebbing, and eventually the disruption and detachment of the tegument, and the breakdown of myofilaments in the muscle cells.