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Evening primrose oil (Oenothera biennis L.)
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Evening primrose oil/Drug Interactions:- AnestheticsAnesthetics: Based on case reports of seizures (13; 14), it has been hypothesized that evening primrose oil (EPO) may increase risk of seizure when used concomitantly with general anesthetics.
- Antiarthritic agentsAntiarthritic agents: Primrose oil may have additive effects when taken concomitantly with antiarthritic agents (35; 36); however, the antiarthritic effects of primrose have not been clearly established.
- Anticoagulants and antiplateletsAnticoagulants and antiplatelets: Theoretically, primrose oil may have additive effects when taken with anticoagulants or antiplatelets, as in vivo research showed that dietary intake of the polyunsaturated omega-6 essential fatty acids (EFAs), linolenic, and gamma-linolenic acids (GLA) increased bleeding time in rats (8).
- Anticonvulsant agentsAnticonvulsant agents: Based on case reports of seizures, it has been hypothesized that evening primrose oil may lower seizure threshold (theoretical).
- Antidepressant agents, monoamine oxidase inhibitors (MAOIs)Antidepressant agents, monoamine oxidase inhibitors (MAOIs): Theoretically, evening primrose may interact with antidepressants.
- Antidepressants, selective serotonin reuptake inhibitors (SSRIs)Antidepressants, selective serotonin reuptake inhibitors (SSRIs): Theoretically, evening primrose may interact with antidepressants.
- AntihypertensivesAntihypertensives: In several rat studies by Engler et al., gamma-linolenic acid, an active constituent of EPO, has been found to decrease central venous blood pressure in both normotensive and hypertensive animals (26; 27; 34; 28). This is potentially due to angiotensin 2 receptor inhibition (29; 30). Preliminary human evidence is equivocal, with some data suggesting a blood pressure-lowering effect in humans (31), and other data showing no effect on blood pressure (6).
- Antineoplastic agentsAntineoplastic agents: Theoretically, primrose oil may have additive effects when taken with antineoplastic agents (37; 38); however, the potential anti-cancer effects of primrose oil are not clearly established.
- Antiobesity agentsAntiobesity agents: Theoretically, primrose oil may have additive effects when taken with antiobesity agents because it has been suggested, but not scientifically proven, to be a weight loss aid (39);(31).
- AntipsychoticsAntipsychotics: There are multiple case reports of seizures occurring in patients taking both EPO and phenothiazine neuroleptics, such as chlorpromazine (Thorazine®), thioridazine (Mellaril®), trifluoperazine (Stelazine®), or fluphenazine (Prolixin®) (13; 14).
- Antiviral agentsAntiviral agents: Theoretically, primrose may have additive effects when taken concomitantly with antivirals (40).
- CNS stimulantsCNS stimulants: Based on case reports of seizures (13; 14), it has been hypothesized that EPO may lower seizure threshold (theoretical).
- Cytochrome P450 2D6 inhibitorsCytochrome P450 2D6 inhibitors: Theoretically, EPO may interact with cytochrome P450 2D6 inhibitors.
- Cytochrome P450 metabolized agentsCytochrome P450 metabolized agents: Theoretically, EPO may interact with cytochrome P450 metabolized agents.
- Gastrointestinal agents, miscellaneousGastrointestinal agents, miscellaneous: Theoretically, EPO may interact with gastrointestinal agents.
- Neurologic agentsNeurologic agents: Theoretically, EPO may interact with neurologic agents, including anticonvulsants (13; 14), antidepressants, phenothiazine neuroleptics, and CNS stimulants.
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Evening primrose oil/Herb/Supplement Interactions:- AnestheticsAnesthetics: Based on case reports of seizures (13; 14), it has been hypothesized that evening primrose oil (EPO) may increase risk of seizure when used concomitantly with general anesthetics.
- Antiarthritic herbs and supplementsAntiarthritic herbs and supplements: Primrose oil may have additive effects when taken concomitantly with antiarthritic agents (35; 36); however, the antiarthritic effects of primrose have not been clearly established.
- Anticoagulants and antiplateletsAnticoagulants and antiplatelets: Theoretically, primrose oil may have additive effects when taken with anticoagulants or antiplatelets, as in vivo research showed that dietary intake of the polyunsaturated omega-6 essential fatty acids (EFAs), linolenic, and gamma-linolenic acids (GLA) increased bleeding time in rats (8).
- AnticonvulsantsAnticonvulsants: Based on case reports of seizures, it has been hypothesized that EPO may lower seizure threshold (theoretical).
- Antidepressant agents, monoamine oxidase inhibitors (MAOIs)Antidepressant agents, monoamine oxidase inhibitors (MAOIs)
: Theoretically, evening primrose may interact with antidepressants.
- Antidepressants, selective serotonin reuptake inhibitors (SSRIs)Antidepressants, selective serotonin reuptake inhibitors (SSRIs)
: Theoretically, evening primrose may interact with antidepressants.
- AntineoplasticsAntineoplastics: Theoretically, primrose oil may have additive effects when taken with antineoplastic agents (37; 38); however, the potential anti-cancer effects of primrose oil are not clearly established.
- Antiobesity herbs and supplementsAntiobesity herbs and supplements: Theoretically, primrose oil may have additive effects when taken with antiobesity agents because it has been suggested, but not scientifically proven, to be a weight loss aid (39);(31).
- Antipsychotic agentsAntipsychotic agents: There are multiple case reports of seizures occurring in patients taking both evening primrose oil and phenothiazine neuroleptics, such as chlorpromazine (Thorazine®), thioridazine (Mellaril®), trifluoperazine (Stelazine®), or fluphenazine (Prolixin®) (13; 14).
- AntiviralsAntivirals: Theoretically, primrose may have additive effects when taken concomitantly with antivirals (40).
- Cytochrome P450 2D6 inhibitorsCytochrome P450 2D6 inhibitors: Theoretically, EPO may interact with cytochrome P450 2D6 inhibitors.
- Cytochrome P450 metabolized herbs and supplementsCytochrome P450 metabolized herbs and supplements: Theoretically, evening primrose oil may interact with cytochrome P450 metabolized herbs and supplements.
- Gastrointestinal herbs and supplementsGastrointestinal herbs and supplements: Theoretically, EPO may interact with gastrointestinal herbs and supplements.
- HypotensivesHypotensives: In several rat studies by Engler et al., gamma-linolenic acid, an active constituent of evening primrose oil, has been found to decrease central venous blood pressure in both normotensive and hypertensive animals (26; 27; 34; 28). This is potentially due to angiotensin 2 receptor inhibition (29; 30). Preliminary human evidence is equivocal, with some data suggesting a blood pressure-lowering effect in humans (31), and other data showing no effect on blood pressure (6).
- Neurologic herbs and supplementsNeurologic herbs and supplements: Theoretically, EPO may interact with neurologic agents, including anticonvulsants (13; 14), antidepressants, and CNS stimulants.
- StimulantsStimulants: Based on case reports of seizures (13; 14), it has been hypothesized that EPO may lower seizure threshold (theoretical).
- ThymeThyme: Theoretically, EPO may have synergistic effects when taken concomitantly with thyme, because a fixed combination of thyme fluid extract and primrose root tincture (Bronchicum® Tropfen) has been used in trials (18; 33).
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Evening primrose oil/Food Interactions:- Insufficient available evidence.
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Evening primrose oil/Lab Interactions:- Blood pressureBlood pressure: In several rat studies by Engler et al., gamma-linolenic acid, an active constituent of evening primrose oil (EPO), has been found to decrease central venous blood pressure in both normotensive and hypertensive animals (26; 27; 34; 28). This is potentially due to angiotensin 2 receptor inhibition (29; 30). Preliminary human evidence is equivocal, with some data suggesting a blood pressure-lowering effect in humans (31), and other data showing no effect on blood pressure (6).
- Coagulation panelCoagulation panel: Theoretically, primrose oil may have additive effects when taken with anticoagulants or antiplatelets, as in vivo research showed that dietary intake of the polyunsaturated omega-6 essential fatty acids (EFAs), linolenic, and gamma-linolenic acids (GLA) increased bleeding time in rats (8).
- Lipid panelLipid panel: A recent study of healthy volunteers given EPO found small changes in serum fatty acid levels, with only GLA demonstrating an absorption-elimination pattern (41).
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Copyright © 2011 Natural Standard (www.naturalstandard.com)
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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.
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