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Uroqid-Acid (Methenamine Mandelate / Sodium Acid Phosphate) - Warnings and Precautions




This product should not be used as the sole therapeutic agent in acute parenchymal infections causing systemic symptoms such as chills and fever.

UROQID-Acid® No.2 contains approximately 83 mg of sodium per tablet and should be used with caution in patients on a sodium-restricted diet.

Sodium phosphates should be used with caution in the following conditions: cardiac failure; peripheral or pulmonary edema; hypernatremia; hypertension; toxemia of pregnancy; hypoparathyroidism; and acute pancreatitis. High serum phosphate levels increase the incidence of extraskeletal calcification.

Large doses of methenamine (8 grams daily for 3 to 4 weeks) have caused bladder irritation, painful and frequent micturition, albuminuria and gross hematuria. Dysuria may occur, although usually at higher than recommended doses, and can be controlled by reducing the dosage. This product contains a urinary acidifier and can cause metabolic acidosis.

Care should be taken to maintain an acidic urinary pH (below 5.5), especially when treating infections due to urea-splitting organisms such as Proteus and strains of Pseudomonas.

Drugs and/or foods which produce an alkaline urine should be restricted. Frequent urine pH tests are essential. If acidification of the urine is contraindicated or unattainable, use of this product should be discontinued.

Information For Patients:   To assure an acidic pH, patients should be instructed to restrict or avoid most fruits, milk and milk products, and antacids containing sodium carbonate or bicarbonate.

Laboratory Tests:   As with all urinary tract infections, the efficacy of therapy should be monitored by repeated urine cultures. During long-term therapy, careful monitoring of renal function, serum phosphorus and sodium may be required at periodic intervals.

Drug Interactions:   Formaldehyde and sulfamethizole form an insoluble precipitate in acid urine and increase the risk of crystalluria; therefore, these products should not be used concurrently. Thiazide diuretics, carbonic anhydrase inhibitors, antacids, or urinary alkalinizing agents should not be used concurrently since they may cause the urine to become alkaline and reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. Concurrent use of antihypertensives, especially diazoxide, guanethidine, hydralazine, methyldopa, or rauwolfia alkaloids; or corticosteroids, especially mineralocorticoids or corticotropin, with sodium phosphates may result in hypernatremia. Concurrent use of salicylates may lead to increased serum salicylate levels since excretion of salicylates is reduced in acidified urine. Serum salicylate levels should be closely monitored to avoid toxicity.

Laboratory Test Interactions:   Formaldehyde interferes with fluorometric procedures for determination of urinary catecholamines and vanilmandelic acid (VMA) causing erroneously high results. Formaldehyde also causes falsely decreased urine estriol levels by reacting with estriol when acid hydrolysis techniques are used; estriol determinations which use enzymatic hydrolysis are unaffected by formaldehyde. Formaldehyde causes falsely elevated 17-hydroxycorticosteroid levels when the Porter-Silber method is used and falsely decreased 5-hydroxyindoleacetic acid (5HIAA) levels by inhibiting color development when nitrosonaphthol methods are used.

Carcinogenesis, Mutagenesis, Impairment Of Fertility: Long-term animal studies to evaluate the carcinogenic, mutagenic, or impairment of fertility potential of this product have not been performed.

Pregnancy:   Teratogenic Effects. Pregnancy Category C. Animal reproduction studies have not been conducted with UROQID-Acid® No.2. It is also not known whether this product can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. Since methenamine is known to cross the placental barrier, this product should be given to a pregnant woman only if clearly needed.

Nursing Mothers:   Methenamine is excreted in breast milk. Caution should be exercised when this product is administered to a nursing woman.

Page last updated: 2006-02-14

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