Suramin (Germanin) is a derivative of a nonmetallic dye whose antiparasitic mechanism of action is not clear. It appears to act on parasite specific -glyc-erophosphate oxidase, thymidylate synthetase, dihydro-folate reductase, and protein kinase but not on host en-zymes.
Suramin is not absorbed from the intestinal tract and is administered intravenously. Although the initial high plasma levels drop rapidly, suramin binds tightly to and is slowly released from plasma proteins, and so it persists in the host for up to 3 months. Suramin neither penetrates red blood cells nor enters the CNS. It is taken up by the reticuloendothelial cells and accumu-lates in the Kupffer cells of the liver and in the epithe-lial cells of the proximal convoluted tubules of the kid-ney. It is excreted by glomerular filtration, largely as the intact molecule.
Suramin is used primarily to treat African try-panosomiasis, for which it is the drug of choice. It is ef-fective in treating disease caused by Trypanosoma gam-biense and T. rhodesiense but not T. cruzi (Chagas’ disease). It can be used alone prophylactically or during the initial hemolymphatic stages of the disease. Later stages, particularly those involving the CNS, are more commonly treated with a combination of suramin and the arsenical melarsoprol.
When CNS involvement occurs, the poor penetra-tion of suramin and pentamidine into the CSF requires alternative forms of chemotherapy, such as melarsoprol in combination with suramin. In treating Onchocerca volvulus infections, suramin kills adult worms and is an alternative to ivermectin. Suramin is used after initial treatment with diethylcarbamazine, which is used to kill the microfilariae. It produces favorable results in pem-phigus and prolongs the time to disease progression in hormone-refractory prostate cancer.
It is important to test for drug sensitivity by admin-istering a small (200 mg) dose by slow intravenous in-jection before giving the full amount of suramin. Since adverse reactions occur with greater frequency and severity among the malnourished, greater caution is necessary for patients with advanced trypanosomiasis. An acute reaction in sensitive individuals results in nau-sea, vomiting, colic, hypotension, urticaria, and even un-consciousness; fortunately, this reaction is rare. Rashes, photophobia, paresthesias, and hyperesthesia may oc-cur later; these symptoms may presage peripheral neu-ropathy. Mild albuminuria is not uncommon, but hema-turia with casts suggests nephrotoxicity and the need to stop treatment.