The most common side effects involve the gastrointestinal system in the form of dyspepsia, upper GIT discomfort, diarrhea or constipation and abdominal pain. Other reactions noted less frequently include transient abnormalities of hepatic or renal function. CNS effects including headache, drowsiness, nervousness and visual disturbances, skin rashes and urticaria. Allergic glomerulonephritis known to be associated with prostaglandin inhibitors, and reversible non-oliguric renal failure has been reported. A positive test for bile in the urine of patients receiving mefenamic acid is not due to the presence of bile, but due to the presence of the drug and its metabolites in the urine. Hematological effects noted with long-term treatment include hemolytic anemia, agranulocytosis, pancytopenia, thrombocytopenia, or thrombocytopenic purpura and bone marrow aplasia.