Drug Breakdown: METHENAMINE

Day 1: #methenamine hippurate is an oral urinary antiseptic discovered in 1859. It has a wide antibacterial spectrum & popularity has been revived because of resistance to UTI antibiotics. Active infection is first cleared with antibiotics & methenamine can then be used if needed for ongoing antibacterial activity is needed

Day 2: #methenamine tablet is licensed in adults & children over 6yrs for prevention of simple lower UTIs. Dose over 12 yrs of age is 1g x2/day or for catheterised adults x2-3/day. Can lead to acid crystal formation, so severe dehydration, Cr Cl<10mls/min & gout are all contra-indicated

Day 3: #methenamine has good GI tract absorption, cmax 1-2 hrs. Highly soluble in water & antibacterial effects begin 30 mins after taking. Decomposes to formaldehyde & ammonia in the urinary tract. If liver impairment, risk of ammonia metabolite accumulation. Renal excretion. T ½ ~4hrs

Day 4: In salt form, the 2 components of #methenamine hippurate are both active. The hippuric acid delivers acidity as, in acidic conditions #methenamine decomposes to formaldehyde. This is a strong antibacterial agent > denaturing bacterial proteins. Hippuric acid also has minor bacteriostatic properties