Oxamniquine, sold under the brand name Vansil among others, is a medication used to treat schistosomiasis due to Schistosoma mansoni.

According to one systematic review, praziquantel is the standard treatment for S. mansoni infections and oxamniquine also appears effective.

[citation needed] Allergic-type reactions, including urticaria, pruritic skin rashes, and fever, may occur.

[9] Oxamniquine is a semisynthetic tetrahydroquinoline and possibly acts by DNA binding, resulting in contraction and paralysis of the worms and eventual detachment from terminal venules in the mesentry, and death.

Its biochemical mechanisms are hypothesized to be related to an anticholinergic effect, which increases the parasite's motility, as well as inhibiting the synthesis of nucleic acids.

The changes caused in the females are reversible and are due primarily to the discontinued male stimulation rather than the direct effect of oxamniquine.

In 1979, Pfizer at Sandwich was presented with the Queen's Award for Technological Achievement in recognition of the outstanding contribution made to tropical medicine by MANSIL (oxamniquine).