Drug interactions
Tolbutamide + Valproic acid
Severity: Moderate
Tolbutamide and Valproic acid: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Valproate can displace tolbutamide from plasma proteins and may inhibit its metabolism, increasing free tolbutamide concentrations. This can enhance the glucose-lowering effect. Hypoglycemia is possible, especially in patients with reduced hepatic or renal function.
What this interaction means in plain words
Tolbutamide and Valproic acid can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Tolbutamide belongs to Endocrine; Valproic acid belongs to Central Nervous System.
Why it happens
Valproate competes for albumin binding and may inhibit CYP2C9-mediated tolbutamide metabolism.
What to do
Monitor blood glucose when valproate is started or stopped. Reduce the tolbutamide dose if hypoglycemia develops.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Valproic acid
- Ertapenem + Valproic acid Contraindicated
- Imipenem / cilastatin / relebactam + Valproic acid Contraindicated
- Imipenem / cilastatin + Valproic acid Contraindicated
- Meropenem / vaborbactam + Valproic acid Contraindicated
- Meropenem + Valproic acid Contraindicated
- Calcium / magnesium / potassium / sodium oxybates + Valproic acid Major
Other interactions of Tolbutamide
- Glyburide-metformin + Tolbutamide Major
- Insulin degludec-liraglutide + Tolbutamide Major
- Aceclofenac + Tolbutamide Moderate
- Acemetacin + Tolbutamide Moderate
- Acetylsalicylic acid + Tolbutamide Moderate
- Albiglutide + Tolbutamide Moderate
Frequently asked questions
Can I take Tolbutamide with Valproic acid?
MediHelp rates the interaction as moderate. Tolbutamide and Valproic acid can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Valproate can displace tolbutamide from plasma proteins and may inhibit its metabolism, increasing free tolbutamide concentrations. This can enhance the glucose-lowering effect. Hypoglycemia is possible, especially in patients with reduced hepatic or renal function.
How serious is the interaction between Tolbutamide and Valproic acid?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood glucose when valproate is started or stopped. Reduce the tolbutamide dose if hypoglycemia develops.
What other medicines interact with Valproic acid?
MediHelp also lists interactions of Valproic acid with, for example, Ertapenem, Imipenem / cilastatin / relebactam, Imipenem / cilastatin. The full list is on the Valproic acid page.
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