Conivaptan and Clindamycin: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 1, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Conivaptan
Clindamycin
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Here's what's going on. Conivaptan (Vaprisol) is a strong blocker of a liver enzyme called CYP3A. Your body uses that same enzyme to break down clindamycin. When conivaptan blocks it, clindamycin can build up higher than usual, which may raise your chance of side effects like stomach upset or diarrhea.
The good news is that this concern is mostly theoretical, and conivaptan is usually given only for a short time in the hospital. Your care team knows how to handle this by spacing out the medicines or watching you more closely. Please don't stop or change either drug on your own, just talk with your pharmacist or doctor.
Mechanism: Conivaptan is a strong CYP3A inhibitor. Clindamycin is partly metabolized by CYP3A4, so inhibition may reduce its clearance and increase systemic exposure (AUC/Cmax).
- Direction: Increased clindamycin exposure (neither drug is a prodrug requiring CYP3A activation).
- Magnitude: Not quantified for clindamycin; conivaptan raised AUC of midazolam, simvastatin, and amlodipine.
- Evidence: Theoretical; onset unspecified.
- Management: Avoid concomitant use. Do not initiate a CYP3A substrate until at least 1 week after completing conivaptan. If co-administered, monitor for concentration-related adverse effects (GI toxicity).
What happens
Increased CYP3A substrate exposure
Interaction Deep Dive
Coadministration of conivaptan, a potent CYP3A inhibitor, with agents that are cleared mainly through CYP3A-mediated metabolism should be avoided, since doing so can raise exposure to the CYP3A substrate. Increases in the AUC of the CYP3A substrates midazolam, simvastatin, and amLODIPine have been observed with conivaptan. A CYP3A substrate should not be started earlier than 1 week following the end of conivaptan treatment1.
Why it happens (mechanism)
Inhibition of CYP3A-mediated substrate metabolism by conivaptan
How to manage this interaction
What your care team may do:
- Prefer to avoid using these two together when possible.
- Wait at least 1 week after finishing conivaptan before starting clindamycin, since conivaptan is usually a short hospital course.
- Watch you more closely for clindamycin-related side effects, such as nausea or diarrhea, if both are needed.
What you should do: Keep taking both exactly as prescribed unless told otherwise. Let your pharmacist or doctor know you are on both so they can time the medicines or monitor you. Report any new or worsening stomach upset or diarrhea.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
3 reports — tap to read
a) When administered as 40 mg/day intravenously, the potent CYP3A inhibitor conivaptan raised the AUC of midazolam, a CYP3A substrate, by roughly 100% following a 1 mg IV dose and by 200% following a 2 mg oral dose 1.
b) Intravenous conivaptan at 30 mg/day produced a threefold increase in the AUC of simvastatin, a CYP3A substrate 1.
c) Conivaptan given as 40 mg orally twice daily led to a doubling of both the AUC and the half-life of amLODIPine, a CYP3A substrate 1.
Common questions
Can I take Conivaptan and Clindamycin together?
Conivaptan can raise clindamycin levels by blocking the CYP3A enzyme, so teams usually avoid combining them and wait about a week after conivaptan before starting clindamycin. Keep taking both as prescribed and check with your pharmacist or doctor. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Conivaptan and Clindamycin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Conivaptan and Clindamycin interaction managed?
What your care team may do: Prefer to avoid using these two together when possible. Wait at least 1 week after finishing conivaptan before starting clindamycin, since conivaptan is usually a short hospital course. Watch you more closely for clindamycin-related side effects, such as nausea or diarrhea, if both are needed. What you should do: Keep taking both exactly as prescribed unless told otherw… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Conivaptan or Clindamycin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: VAPRISOL(R) intravenous injection, conivaptan HCl intravenous injection. Cumberland Pharmaceuticals Inc. (per manufacturer), Nashville, TN, 2014.
Keep reading about Conivaptan
Keep reading about Clindamycin
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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