Evening Primrose - Paxlovid (Nirmatrelvir, Ritonavir) Interaction
Herbal: Evening Primrose
Also Known As: Oenothera biennis, Oenothera muricata, Oenothera rubricaulis, Evening star, Suncups, Sundrop
Drug: Nirmatrelvir, Ritonavir
Brand names:
Paxlovid
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
May 25, 2025
Interaction Details
Nirmatrelvir, Ritonavir is classified as belonging to the following category: Lopinavir/Ritonavir (Kaletra)
Theoretically, evening primrose oil might increase the levels and effects of lopinavir.
In a case report, an HIV patient who took evening primrose oil (Efamol) along with lopinavir/ritonavir experienced an increase in serum levels of lopinavir to 15.2 mg/L. Six weeks after discontinuing evening primrose oil, levels of lopinavir returned to the normal range of 5-10 mg/L. When re-challenged with evening primrose oil for a week, the patient's lopinavir levels increased from 6.69 to 8.11 mg/L. It is suspected that evening primrose oil increases levels of lopinavir by inhibiting cytochrome P450 3A4 (CYP3A4), which metabolizes lopinavir. However, this effect has not been reported in other research.
Interaction Rating
Likelihood of Occurrence
PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
References
- Jalloh MA, Gregory PJ, Hein D, et al. Dietary supplement interactions with antiretrovirals: a systematic review. Int J STD AIDS. 2017 Jan;28(1):4-15.
Evening Primrose Overview
Evening primrose (Oenothera biennis) is a plant native to North and Central America and a member of the Onagraceae family. It is an annual plant that has bright yellow flowers that bloom in the evening (hence the name). The plant produces seeds that are rich in a fatty acid called gamma-linolenic acid (GLA).
Evening primrose oil is a dietary supplement that is derived from the seeds of the evening primrose plant. It is rich in GLA (gamma-linolenic acid), an omega-6 fatty acid, and is sometimes taken to improve the health of the skin, reduce inflammation, and reduce the symptoms of premenstrual syndrome (PMS). It has also been used historically for alcohol use disorder.
Dietary supplements containing evening primrose oil generally are standardized by their gamma-linolenic acid (GLA) and linoleic acid (LA) content.
Evening Primrose - More Interactions
Evening Primrose interacts with 229 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
| Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
| Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
| Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
| Unknown | No interactions have been reported or no interaction data is currently available. |
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Parts of this content are provided by the Therapeutic Research Center, LLC.
DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.
© 2021 Therapeutic Research Center, LLC
Drug descriptions are provided by MedlinePlus.
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