More and more people are using essential oils to support their wellness goals. When used as intended and with common sense, the overall safety of essential oils is impressive and has been documented.
Still, it’s important to remember that the beautiful secondary metabolites that make up essential oils and enhance our wellness are not inert. In other words, these oils have some powerful biochemical actions and that’s why they can modulate health in a variety of ways!
I’ve been requested several times to write about essential oil-drug interactions. This is a huge subject and it is nearly impossible to come up with a definitive answer due to the various qualities of oils that are available, standardizations, and different schools of aromatherapy. Furthermore, I am not a biochemist. Still, I do love biochemistry and I am a pretty good researcher.
With the explosion of interest, I felt it was time to dive into the research. Also, in excitement and anticipation of my upcoming book release, I thought it was a great time to give you a gift!
So, here is a taster of the kind of information you’ll get from my upcoming book!
Before I get into specifics, here are some important general considerations regarding the use of essential oils and medications:
- They both influence the organs of elimination and excretion, therefore, it’s important to monitor your response and assess with your doctor the dosage throughout use. You may need to tweak things with the introduction of natural therapies.
- Everyone is different, with different detoxification capacities and abilities to metabolize drugs, supplements, and nutrients. Therefore, be aware of your body and listen to its response.
- Space out medications at least 2-3 hours from using essential oils. If on a “blood thinner”, only use oils if your physicians are monitoring “clotting time” (PT/PTT/INR).
- Oils do have limited metabolism in the liver and are then peed and breathed out. In geek terms, according to Therapeutic Benefits of Essential Oils, Nutrition, Well-Being and Health, most components of essential oils are taken in then metabolized by limited phase I, followed by glucuronidation and sulfation and then through the kidneys as polar compounds or exhaled through the lungs as CO2. (1) So, if you are finding you are peeing a lot on oils, you may want to decrease your dose a bit.
Now, the specifics…
The Grapefruit Oil Controversy: To Be or Not to Be (Bergamottin or DHB)
Grapefruit juice (GFJ) can be a major inhibitor of drugs due to the presence of furanocoumarins. Human studies suggest that bergamottin and 6,7-dihydroxybergamottin (DHB), are the primarily furanocoumarins responsible for drug interactions with grapefruit juice. (2)
According to the essential oil pharmacist, “While bergamattin and bergapten are found in grapefruit oil and other citrus oils, the likelihood of them causing clinically important drug interactions is much lower than with DHB or flavonoids.” (3)
I think it’s important to point out that citrus essential oils, though pressed from the peel, have volatile constituents that predominate and tend to balance the non-volatile constituents. For example, in simple terms, Mr. Wiki states, “A clear liquid (sometimes there is a deposit consisting of waxes) in color from green to greenish yellow, bergamot essential oil consists for the most part (average 95%) of a volatile fraction and for the remaining (5%) of a non-volatile fraction (or residual). Chemically it is a highly complex mixture of many classes of organic substances, particularly for the volatile fraction terpenes, esters, alcohols and aldehydes, and for the non-volatile fraction, oxygenated heterocyclic compounds as coumarins and furanocoumarins.”
For me, if there is a potential interaction with some of the constituents present in the oil, I’d suggest using a different citrus oil if one is on blood pressure medications or other medications that can interact with the liver enzymatic pathway that furanocoumarins modulate, though the levels are very, very low. Your doctor can help reference which medications these are.
**Update On Citrus Oils and Dishing Out the Juicy Info
Stephanie, a reader of the blog, pointed out to me that lime, bergamot, and orange (Seville) also contain furanocoumarins. (I love my smart readers!) Below is the result of my resources (and her’s) to clarify. Ratings are based on a combination of the level of evidence (quality of the trial), severity of occurrence, and probability based on extensive research reviews:
There are some studies that show an effect with these JUICES. Grapefruit juice and grapefruit have the additional evidence of inhibiting intestinal P-glycoprotein, which further rises the drug levels in some people, earning its reputation for more cautious imbibing in medication users. (Again, please note these are the nonvolatile fractions, as stated above.) Still, here goes..
Lime: This interaction is listed as “moderate” (cautious) on Natural Standard Database for lime. Still, for those with compromised CYP3A4 SNP may want to be weary of lime with felodopine, as this was a study in human response.
Orange: Orange is also listed as “moderate” in Natural Standard Database. It appears it may not inhibit the intestinal P-glycoprotein as grapefruit does.
Bergamot: Interestingly, bergamot is rated as “moderate” for CYP3A4 drugs, but “major” for Versed (the juice).
This study examined the furanocoumarins in various citrus oil peels and pulps. Interestingly, the study states more of the compounds that show interactions in grapefruit are in the pulp, an exception, “bergamottin, a bergapten-geranylated derivative, which is regularly found more concentrated in the pulp of pummelos (Deep Red, Chandler) and their hybrid grapefruits (Duncan, Marsh) and sour oranges (Maroc, Bouquettier de Nice, Granito).”
It will be interesting to see if more studies are done if all types of furanocoumarins have the same interactions as with bergamottin and 6,7-dihydroxybergamottin (DHB) in human trials, as the evidence is limited so far…but enough to mention safety. Obviously, grapefruit and bergamot, (with honorable eyebrow raisers lime and orange) are the main players with actual evidence
Bottom line: Those on drugs that inhibit this pathway should monitor for effects over the short and long-term and inform their docs. For most citrus oils, besides grapefruit and those listed above, the evidence is not very high. Furthermore, the EO Pharmacist also ensures us that the levels of these compounds are lower than the juice extractions.
(If anyone has any more clarifications or insights, please share!)
The Peppermint Pathways
Due to peppermint’s ability to modulate motility of the digestive tract in vitro and in vivo, any medications that affect digestion can potentially interact with peppermint oil. Furthermore, drugs that decrease stomach pH, such as H2 blockers or proton pump inhibitors, could potentially cause enteric coated capsules of peppermint to dissolve earlier. (Enteric coating is used to prevent absorption in the stomach). Natural Standard Database also reports potential interactions with that liver enzyme, CYP450. However, this is more theoretical evidence and has not been demonstrated in humans. (4,5)
Peppermint and nifedipine interactions were studied in vitro using human liver cells. Peppermint oil and its constituents menthol, menthyl acetate moderately, reversibly inhibited an enzyme in the liver, CYP3A4. This may cause an increase amount in the body of this calcium channel blocker that is used for high blood pressure levels. However, the researchers noted, “this requires further investigation.” (6)
Essential oils Cautions for Pregnancy & Medications
The following information is from my 3rd ed.of the Essential Oil Desk Reference.
Safe oils: geranium, German chamomile, neroli, sandalwood, rosewood, gentle baby, lavender, myrrh , rose.
Avoid: basil, calamus, clary sage, fennel, hyssop, nutmeg, rosemary, sage, tansy, tarragon.
High blood pressure and epilepsy medications
Caution with basil, hyssop, fennel, peppermint, nutmeg, rosemary, sage, tansy, tarragon.
Avoid sage and rosemary with high blood pressure medications.
(Note, sometimes if you have a doc versed in both oils and medications, these can be monitored. For example, there are no “major” interactions with rosemary according to Natural Standard with rosemary. The University of Maryland; however, advises to avoid it. )
The following oils contain coumarins or other constituents that may interfere with blood thinners. However, if anyone is on blood thinners, any changes with any supplement or medication should be followed by their doctor due to levels needing to be in range…
Avoid angelica, birch, cinnamon, clove, fir (balsam), helichyrsm, Laurus nobilis, nutmeg, oregano, wintergreen, unless you are being monitored by your doctor on levels.
Potential interaction: In a rodent study, the essential oil (EO) of caraway, prepared as emulsion, was applied to male mice for 5 consecutive days. Paracetamol, in the dose of 200 mg/kg, was applied orally or injection 2 hours after the last EO dose. Following this, blood samples were taken at various time intervals. With oral dosage, there was less paracetamol in the rodent’s body. After injection, there was enhanced body exposure to the drug with the EO. (7)
Potential interaction: The effects of codeine, diazepam, midazolam, pentobarbital, imipramine and fluoxetine were tested in mice after 5days of pretreatment of aniseed EO and there were various modulatory effects between medications and anise EO. (8)
So, there it is. I hope you found it helpful!
If you want to really dive into using natural medicine safely and evidence-based, stay tuned for my upcoming book, BreakFree Medicine.
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Disclaimer: This information is applicable ONLY for therapeutic quality essential oils. This information DOES NOT apply to essential oils that have not been assessed for quality, purity, and standardization of constituents.
Warning: There is no quality control in the United States for essential oils and oils labeled as “100% pure” need only contain 5% of the actual oil! The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin and body.
This information is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness.
(1) Djilani, A & Dicko, A. The Therapeutic Benefits of Essential Oils, Nutrition, Well- Being and Health. Dr. Jaouad Bouayed ed. 2012; 160.
(2) Natural Standard Database. Grapefruit Juice. (Professional Database-Subscription Required).
(3) Lindsey Elmore. Grapefruit Oil and Medications. The Farmacist. February 8, 2015. http://www.thefarmacistalabama.com/blog/
(4) Dresser GK1, Wacher V, Wong S, Wong HT, Bailey DG. Evaluation of peppermint oil and ascorbyl palmitate as inhibitors of cytochrome P4503A4 activity in vitro and in vivo. Clin Pharmacol Ther. 2002 Sep;72(3):247-55.
(5) Natural Standard Database. Peppermint Oil. (Professional Database-Subscription Required).
(6) Goerg KJ, Spilker TH. Effect of peppermint oil and caraway oil on gastrointestinal motility in healthy volunteers: a pharmacodynamic study using simultaneous determination of gastric and gall-bladder emptying and orocaecal transit time. Aliment Pharmacol Ther. 2003; 17: 445–451.
(7) Samojlik I, Ðakovi?-Švajcer K, Božin B, Mikov M. Herb-drug interactions: the influence of essential oil of caraway (Carum carvi L.) on the pharmacokinetics of paracetamol. BMC Pharmacology & Toxicology. 2012;13(Suppl 1):A27. doi:10.1186/2050-6511-13-S1-A27.
(8) Samojlik I1, Mijatovi? V, Petkovi? S, Skrbi? B, Božin B.The influence of essential oil of aniseed (Pimpinella anisum, L.) on drug effects on the central nervous system.Fitoterapia. 2012 Dec;83(8):1466-73. doi: 10.1016/j.fitote.2012.08.012. Epub 2012 Aug 25.
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