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Questions And Answer

• Pharmacology and mechanism of action

  Oxamniquine is a tetrahydroquinoline derivative effective in the treatment of Schistosoma(s) mansoni infections. The male worms are more susceptible to the drug effects than the female ones. It has no therapeutic value against other Schistosoma species. In experimental animal models, the drug causes a shift of the worms from the mesenteric veins to the liver where the male and the female decouple. The male worms preferentially concentrate the drug and die in the liver. The unpaired females return to the mesenteric vessels where they cease laying eggs and eventually die ^[1]. The mechanism of action of Oxamniquine is unknown. The drug may induce its action by inhibiting DNA synthesis. When the drug was administered to rats infected with S. mansoni, it inhibited the synthesis of macromolecules in sensitive parasites and not in the resistant ones ^[2]. ;

• Indications

  Oxamniquine is used against S. mansoni infections, including advanced cases with hepatomegaly, ascites or with colonic polyposis. ;

• Side effects

  Oxamniquine is generally well tolerated even during large scale treatment programmes. The only significant common side effect reported is mild to moderate dizziness with or without drowsiness, reported by up to 40% of treated patients. It starts up to 3 hours after a dose and usually lasts for 3 to 6 hours. Other side effects include nausea, vomiting, abdominal pain, and diarrhoea ^[3]. Transient fever, 38 to 39°C, peripheral blood eosinophilia and pulmonary infiltrates (Loeffler’s syndrome) have been reported mainly from Egyptian patients 24 to 72 hours after completing a 3-day course of therapy ^[4]. The cause seems to be unknown. A number of reports of epileptiform convulsions have been reported in patients suspected with ^[5] or without ^[6,7]a history of epilepsy. More severe neuropsychiatric symptoms such as severe headache, hallucinations, episodes of fainting, severe amnesia, total disorientation in space and time and confusion have been rarely reported ^[8,9]. Discoloration of the urine from orange to red may follow after the drug treatment (most likely due to a metabolite) ^[10]. This is transitory and harmless, nevertheless patients should be informed about it. ;

• Contraindications and precautions

  Patients with pre-existing central nervous system disturbances such as epilepsy or psychiatric disorders should be treated with caution. ;

• Preparations

  • Vansil® (Pfizer). Capsules 250 mg. Oral suspension 50 mg/ml.
  • Mansil® (Pfizer). Capsules 250 mg. Oral suspension 50 mg/ml. ;

• References

  1. Webster LT Jr (1990). Drugs used in the chemotherapy of helminthiasis. In: Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 8th edn, edited by A.G.Gilman, T.W.Rall, A.S.Nies, P Taylor, (New York: Pergamon Press), pp. 966.
  2. Pica-Mattoccia L, Coli D (1985). Studies on the mode of action of oxamniquine and related schistosomicidal drugs. Am J Trop Med Hyg, 34, 112–118.
  3. Foster R (1987). A review of clinical experience with oxamniquine. Trans R Soc Trop Med Hyg, 81, 55–59.
  4. Higashi GI, Farid Z (1979). Oxamniquine fever: drug-induced or immune-complex reaction BMJ, ii, 830.
  5. Krajden S, Keystone JS, Glenn C (1983). Safety and toxicity of oxamniquine in the treatment of Schistosoma mansoni infections, with particular reference to electroencephalographic abnormalities. Amer J Trop Med Hyg, 32, 1344–1346.
  6. Stockvis H, Bauer AGC, Stuiver PC, Malcolm AD, Overbosche D (1986). Seizures associated with oxamniquine therapy. Am J Trop Med Hyg, 35, 330–331.
  7. Al-aska AK (1985). Treatment of Schistosoma mansoni infection with oxamniquine in Riyadh, Saudi Arabia. Trop Med Parasitol, 36, 213–214.
  8. Katz N, Grinbaum E, Chaves A, Zicker F, Pellegrind J (1976). Clinical trials with oxamniquine by oral route, in Schistosoma mansoni. Rev Inst Med Trop São Paulo, 18, 371–377.
  9. Chunge CN, Kimani RG, Gachihi G, Mkoji G, Kamau T, Rashid JR (1985). Serious side effects
  10. Anthelminthics. Martindale: The Extra Pharmacopoeia, 30th edn (1993), (London: Pharmaceutical Press), pp: 4950. ;

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