RESUMEN
In this study we evaluated the acute (immobility/mortality) and chronic (survival and reproduction) effects of the drugs caffeine, diclofenac sodium salt, ketoprofen, paracetamol and salicylic acid on the cladoceran Ceriodaphnia silvestrii. The environmental risks of these substances for tropical freshwaters were estimated from the risk quotient MEC/PNEC. Sensitivity in acute exposures varied up on the drug as follows: salicylic acid (EC50 = 69.15 mg L- 1) < caffeine (EC50 = 45.94 mg L- 1) < paracetamol (EC50 = 34.49 mg L- 1) < ketoprofen (EC50 = 24.84 mg L- 1) < diclofenac sodium salt (EC50 = 14.59 mg L- 1). Chronic toxicity data showed negative effects of the drugs on reproduction. Paracetamol and salicylic acid caused reduction in fecundity in concentrations starting from 10 mg L- 1 and 35 mg L- 1, respectively. Ketoprofen caused total inhibition at 5 mg L- 1. MEC/PNEC values were relatively low for all drugs. The risk was estimated as low or insignificant, except for caffeine, whose MEC/PNEC value was greater than 1 (moderate risk).