What the FDA labels say about taking them together
Methenamine and metolazone
Metolazone's FDA label of December 11, 2025 names methenamine in its drug interactions section; the methenamine labels PlainMeds reads (2) do not name metolazone. The metolazone label: “Methenamine Efficacy may be decreased due to urinary alkalizing effect of metolazone.”
Check it at the source: the methenamine FDA label on DailyMed (effective August 7, 2026, ANI Pharmaceuticals, Inc.); the metolazone FDA label on DailyMed (effective December 11, 2025, Unichem Pharmaceuticals (USA), Inc.).
What does the methenamine label say about metolazone?
Methenamine's label (effective August 7, 2026) and its 1 other brand-application label do not name metolazone in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Methenamine Hippurate), ANI Pharmaceuticals, Inc., effective August 7, 2026 (SPL set a3eeacd4-1983-49ec-a60d-3abaf505ce57), via openFDA; the full label on DailyMed
What does the metolazone label say about methenamine?
Metolazone label, drug interactionsMethenamine Efficacy may be decreased due to urinary alkalizing effect of metolazone.
Source: FDA drug label (Metolazone), Unichem Pharmaceuticals (USA), Inc., effective December 11, 2025 (SPL set c6fe5426-a184-44b8-a555-621d72aa5b9f), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Methenamine | Metolazone | |
|---|---|---|
| Labeled for | Urinary tract infections | High blood pressure, Edema (fluid retention), Heart failure |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.313 per tablet 1 g tablet | $0.233 per tablet 2.5 mg tablet |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once