Drug General Information (ID: DDIDYRCP7U)
Drug Name			Lactic acid		Drug Info		Methenamine		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Topical Agents				Urinary Antispasmodics
Structure

Mechanism of Lactic acid-Methenamine Interaction (Severity Level: Moderate)
Altered urine pH Click to Show/Hide Mechanism Graph
Drug Name		Lactic acid				Methenamine
Mechanism		Urine alkalinizer				Urine pH sensitive
Key Mechanism Factor 1
		Factor Name		Urine pH
		Factor Description		The normal range of urine pH is between 4.5 and 8, depending mainly on the hydrogen ion concentration. Changes in urine pH may significantly affect drug reabsorption and excretion.
Mechanism Description		Altered elimination of Methenamine caused by Lactic acid mediated altered urine pH

Recommended Action
Management		Concomitant use of methenamine-containing preparations with thiazide diuretics, carbonic anhydrase inhibitors, or large doses of antacids should be avoided if possible. Otherwise, frequent urine pH testing may be considered. Some methenamine products may be used with antacids if dosing times are separated by at least one hour. Consult the manufacturer's product labeling for specific recommendations.

References
1	Kevorkian C, Merritt J, Ilstrup D "Methenamine mandelate with acidification: an effective urinary antiseptic in patients with neurogenic bladder." Mayo Clin Proc 59 (1984): 523. [PMID: 6379319]
2	Musher D, Griffith D "Generation of formaldehyde from methenamine: effect of pH and concentration, and antibacterial effect." Antimicrob Agents Chemother 6 (1974): 708-11. [PMID: 4451344]
3	Product Information. Hiprex (methenamine). Hoechst Marion-Roussel Inc, Kansas City, MO.