Fever Plant
Scientific Name: Evening Primrose
Other Names: OEP, Oenothera species, Sun Drop
What interactions should I watch for?
Prescription Drugs
In studies and case reports, GLA has been shown to increase the time blood needs to clot. Due to the high percentage of GLA in evening primrose oil, blood-thinning effects may be increased if evening primrose oil is taken at the same time as an antiplatelet or anticoagulant drug, possibly resulting in uncontrolled bleeding.
- Antiplatelets include clopidogrel and Ticlid
- Anticoagulants include heparin and warfarin
Reportedly, seizures have been attributed to taking evening primrose oil at the same time as some drugs for treating schizophrenia. Avoid using evening primrose oil while taking drugs such as:
- chlorpromazine
- fluphenazine
- prochlorperazine (Compazine)
- promethazine (Phenergan)
- thioridazine
- trifluoperazine
Although no cases have been reported in scientific literature, evening primrose oil possibly may interfere with the effects of medications to treat epilepsy. Avoiding oral evening primrose oil is recommended for individuals who take anti-epileptic drugs that include:
- barbiturates such as phenobarbital
- benzodiazepines such as diazepam
- carbamazepine (Tegretol)
- Cerebyx
- gabapentin (Neurontin)
- Keppra
- Lamictal
- phenytoin (Dilantin)
- Topamax
- valproic acid (Depakene)
Non-prescription Drugs
The GLA in evening primrose oil may lessen the ability of blood to clot after an injury. Aspirin can also delay clotting, so evening primrose oil should not be taken orally at the same time as aspirin.
Some non-prescription products such as dexchlorpheniramine (an antihistamine) and pseudoephedrine (a decongestant) possibly may make seizures more likely to recur. Although the risk is thought to be slight, taking evening primrose oil may also increase the possibility of seizures for individuals who have had seizures previously, so taking evening primrose oil at the same time as non-prescription antihistamines or decongestants is not recommended.
Herbal Products
Theoretically, if evening primrose oil is used with other herbs that affect blood clotting, bleeding may occur. Some of the most common herbal products that might inhibit blood clotting are:
- Danshen
- Devil's Claw
- Eleuthero
- Garlic
- Ginger (in high amounts)
- Gingko
- Horse Chestnut
- Panax Ginseng
- Papain
- Red Clover
- Saw Palmetto
Based on the results of older studies that have not been recreated, evening primrose oil possibly may "lower the seizure threshold", which means it may make seizures more likely to recur in individuals who have had previous seizures. When evening primrose oil is taken with other herbal products that may also induce seizures, the risk increases. Some other herbals that may lower the seizure threshold include:
- Borage
- Ginkgo
- Juniper
- Wormwood
Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how evening primrose interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.
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What interactions should I watch for?
