Methyldopa and Vasopressin Interaction
Drug interaction information between Methyldopa and Vasopressin.
Methyldopa and Vasopressin have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Methyldopa and Vasopressin. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Methyldopa can cause the body to retain extra water, which boosts the blood pressure and water-saving effects of vasopressin.
FDA Label Information
7.4 Drugs Suspected 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 injection.
Methyldopa Also Interacts With
- Ferrous Sulfate moderate
- Carbidopa/Levodopa moderate
- Tranylcypromine moderate
- Lithium minor
- Colestipol minor
Vasopressin Also Interacts With
- Nirmatrelvir/Ritonavir major
- Itraconazole moderate
- Lithium minor
- Enalapril minor
- Haloperidol minor
Frequently Asked Questions
What SPL severity band is on file for Methyldopa + Vasopressin?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Vasopressin has 9 labeled pairs on file vs Methyldopa's 7. In the minor band specifically: Methyldopa has 4 (also Lithium, Colestipol, Enalapril); Vasopressin has 7 (also Lithium, Enalapril, Haloperidol, Clozapine).
What mechanism field is on file for Methyldopa and Vasopressin?
Methyldopa can cause the body to retain extra water, which boosts the blood pressure and water-saving effects of vasopressin.
Vasopressin carries more major-labeled pairs than Methyldopa
SPL source-record counts only. This page's band is minor · classes on file: Methyldopa (Central Alpha-2 Agonist); Vasopressin (Vasopressin Receptor Agonist).
Vasopressin has 1 major-labeled pair vs Methyldopa's 0. This page itself is in the minor band, not the major band.
0 major · 3 moderate · 4 minor · 7 total
- Other minor peers for Methyldopa
- Lithium
- Colestipol
- Enalapril
1 major · 1 moderate · 7 minor · 9 total
- Other minor peers for Vasopressin
- Lithium
- Enalapril
- Haloperidol
- Clozapine
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.