<p>Prolonged full dose treatment with sulfamethoxazole-trimethoprim combination is associated with the risk of macrocytic anaemia due to the drug&rsquo;s interference in the conversion of Folic acid into Folinic acid. If this occurs, it can be reversed by giving Folinic acid. Care should be taken when giving this combination to diabetic patients receiving sulphonylurea drug for possible potentiation of action of sulphonylurea.</p>