Ritonavir and Dihydroergotamine Nasal Spray: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ritonavir
Dihydroergotamine Nasal Spray
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.
What happens
Increased ergot derivatives exposure and an increased risk of ergotism (nausea, vomiting, vasospastic ischemia)
Interaction Deep Dive
The concomitant administration of ritonavir and ergot derivatives is contraindicated as it may result in increased plasma concentration of ergot derivatives. It also has the potential for serious and/or life-threatening reactions such as acute ergot toxicity characterized by peripheral vasospasm and ischemia of the extremities and other tissues21.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by ritonavir
Literature reports
1 report — tap to read
a) A 34-year-old HIV positive female presented to the emergency room with dizziness, loss of vision, headache, vomiting, diarrhea, and feeling of cold in her left foot after receiving ergotamine tartrate and ritonavir. Her current drug regimen included ritonavir, lamiVUDine and stavudine, which she had been taking for the past 3 years to treat HIV infection. She had taken three ergotamine tartrate tablets during the 4 days preceding the onset of signs and symptoms. Physical exam revealed an arterial blood pressure of 160/60 mm Hg, a heart rate of 80 beats/min, the absence of peripheral pulses in all 4 extremities, and acral cyanosis. The patient went in and out of consciousness throughout her stay in the emergency room. She was admitted to the intensive care unit and 24 hours later had a decrease in level of consciousness, as well as arterial hypotension, and orotracheal intubation was necessary. Systemic arteriography demonstrated signs of stenosis and vasospasm in medium and large vessels that diffusely affected the mesenteric, renal, femoral, humeral, and internal carotid arteries, with cerebral hypoperfusion. There was no response to intra-arterial infusion of niMODipine. Treatment with a perfusate containing DOBUTamine, corticosteroids, and heparin was initiated, but there was no response to treatment. Alprostadil was added to the perfusate for 7 days, but there was no response to treatment. The patient's neurological state deteriorated and she remained in coma vigil. Multiple subcortical infarcts were revealed on a cranial CT scan. Arteriography performed one month after the onset of symptoms revealed vasospasm to have disappeared from all previously involved arteries. Two years after the diagnosis was made there was no change in the patient's neurological state (coma vigil) 2.
Common questions
Can I take Ritonavir and Dihydroergotamine Nasal Spray together?
Increased ergot derivatives exposure and an increased risk of ergotism (nausea, vomiting, vasospastic ischemia) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ritonavir and Dihydroergotamine Nasal Spray interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Ritonavir or Dihydroergotamine Nasal Spray 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 (2)
Keep reading about Ritonavir
Keep reading about Dihydroergotamine Nasal Spray
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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