What the FDA labels say about taking them together
Methyldopa and vasopressin
Vasopressin's FDA label of February 21, 2025 names methyldopa in its drug interactions section; the methyldopa label PlainMeds reads does not name vasopressin. The vasopressin label: “Suspected of Causing SIADH Use with drugs suspected of causing SIADH may increase the pressor effect in addition to the antidiuretic effect of Vasostrict ®.”
Check it at the source: the methyldopa FDA label on DailyMed (effective March 26, 2025, Chartwell RX, LLC); the vasopressin FDA label on DailyMed (effective February 21, 2025, Baxter Healthcare Corporation).
What does the methyldopa label say about vasopressin?
Methyldopa's label (effective March 26, 2025) does not name vasopressin in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Methyldopa), Chartwell RX, LLC, effective March 26, 2025 (SPL set e1114a58-9ab5-486e-85ed-360365b06396), via openFDA; the full label on DailyMed
What does the vasopressin label say about methyldopa?
Vasopressin label, drug interactionsSuspected of Causing SIADH Use with drugs suspected of causing SIADH (e.g., SSRIs, tricyclic antidepressants, haloperidol, chlorpropamide, enalapril, methyldopa, pentamidine, vincristine, cyclophosphamide, ifosfamide, felbamate) may increase the pressor effect in addition to the antidiuretic effect of Vasopressin in Sodium Chloride Injection.
Source: FDA drug label (Vasostrict, NDA204485), Par Health USA, LLC, effective April 21, 2026 (SPL set b1147beb-743e-4c62-8927-91192447f8b8), via openFDA
Source: FDA drug label (Vasopressin, NDA212593), American Regent, Inc., effective October 31, 2024 (SPL set 0ab267f4-9ec9-44fd-8521-f975074667d9), via openFDA
Source: FDA drug label (Vasopressin in 0.9% Sodium Chloride), Baxter Healthcare Corporation, effective February 21, 2025 (SPL set b5b2c367-6b7e-40be-a296-c4632f3e783f), 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
| Methyldopa | Vasopressin | |
|---|---|---|
| Labeled for | n/a | n/a |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | n/a |
| 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