Mebendazole compared with secnidazole-adult giardiasis-Phase III

INTERVENTION: Group I (Experimental): Mebendazole 200 mg by oral route three times during three days, (64 patients). Group II (Control): Secnidazole 2g by oral route in a single dose, a single day, (62 patients). CONDITION: Giardiasis PRIMARY OUTCOME: Parasitological answer (Cured: If no Giardia cysts or trophozoites be found in any of the three post‐treatment faecal simples, Not cured: Other case (microscopical examination as direct wet mount and Ritchie concentration. Measuring time: 3, 5 and 7 days after treatment completion. Clinical answer (Without clinical manifestations, with a relieve of the clinical manifestations, with the same clinical manifestations). Measuring time: 12 days after treatment completion. SECONDARY OUTCOME: Adverse Events (description of the events). Measuring time: 3 days after treatment completion. Intensity of AE (Slight, moderate or severe, taking into account the grade of disfunction produced by the event). Measuring time: 3 days after treatment completion. INCLUSION CRITERIA: Informed‐consent form signed. Patients with 18 years and older.