What the FDA labels say about taking them together
Amphetamine and methenamine
Amphetamine's FDA label of August 20, 2026 names methenamine in its drug interactions section; the methenamine labels PlainMeds reads (2) do not name amphetamine. The amphetamine label: “Methenamine therapy Urinary excretion of amphetamines is increased, and efficacy is reduced by acidifying agents used in methenamine therapy.”
Check it at the source: the amphetamine FDA label on DailyMed (effective August 20, 2026, Aurolife Pharma, LLC); the methenamine FDA label on DailyMed (effective August 7, 2026, ANI Pharmaceuticals, Inc.).
What does the amphetamine label say about methenamine?
Amphetamine label, drug interactionsMethenamine therapy Urinary excretion of amphetamines is increased, and efficacy is reduced by acidifying agents used in methenamine therapy.
Source: FDA drug label (Amphetamine Sulfate), Aurolife Pharma, LLC, effective August 20, 2026 (SPL set 20735c2e-6304-425f-a4e4-584f6f90d6a0), via openFDA; the full label on DailyMed
What does the methenamine label say about amphetamine?
Methenamine's label (effective August 7, 2026) and its 1 other brand-application label do not name amphetamine 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
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
| Amphetamine | Methenamine | |
|---|---|---|
| Labeled for | ADHD | Urinary tract infections |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.449 per tablet 10 mg tablet | $0.313 per tablet 1 g 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