Vitamin D - Premarin (Conjugated Estrogens) Interaction
Herbal: Vitamin D
Also Known As: Ergocalciferol, Cholecalciferol
Drug: Conjugated Estrogens
Brand names:
Premarin, Cenestin, Enjuvia, Premarin Vaginal Cream
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Jun 15, 2025
Interaction Details
Conjugated Estrogens is classified as belonging to the following category: Cytochrome P450 3A4 (Cyp3A4) Substrates
Vitamin D might induce CYP3A4 enzymes and reduce the bioavailability of CYP3A4 substrates.
There is some concern that vitamin D might induce CYP3A4. In vitro research suggests that vitamin D induces CYP3A4 transcription. Additionally, observational research has found that increased UV light exposure and serum vitamin D levels are associated with decreased serum levels of CYP3A4 substrates such as tacrolimus and sirolimus, while no association between UV light exposure or vitamin D levels and levels of mycophenolic acid, a non-CYP3A4 substrate, was found. A small, low-quality clinical study shows that taking vitamin D reduces levels of the CYP3A4 substrate atorvastatin and its active metabolites by up to 55%; however, the clinical effects of atorvastatin were not reduced. While researchers theorized that vitamin D might induce CYP3A4, this proposed mechanism was not specifically studied.
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
- Schwartz JB. Effects of vitamin D supplementation in atorvastatin-treated patients: A new drug interaction with an unexpected consequence. Clin Pharmacol Ther 2009;85:198-203.
- Wang Z, Schuetz EG, Xu Y, Thummel KE. Interplay between vitamin D and the drug metabolizing enzyme CYP3A4. J Steroid Biochem Mol Biol 2013;136:54-8.
Vitamin D Overview
Vitamin D is a fat-soluble vitamin that plays a crucial role in several bodily processes. It helps the body absorb calcium and phosphorus, which are necessary for healthy bones and teeth. It is also important for immune system function and may help to protect against certain diseases.
Vitamin D is found in a variety of foods, including fatty fish, egg yolks, and fortified foods such as milk and cereal. It is also produced by the body when the skin is exposed to sunlight.
Vitamin D supplements are available in a variety of forms, including tablets, capsules, and liquids. The recommended daily intake of vitamin D varies depending on age, sex, and other factors, and it is important to follow the dosage recommendations provided by a healthcare professional. There are several different forms of vitamin D available, with the two most popular being ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
Conjugated Estrogens Overview
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The estradiol cypionate and estradiol valerate forms of estrogen injection are used to treat hot flushes (hot flashes; sudden strong feelings of heat and sweating) and/or vaginal dryness, itching, and burning in women who are experiencing menopause (change of life; the end of monthly menstrual periods). However, women who need a medication only to treat vaginal dryness, itching, or burning should consider a different treatment. These forms of estrogen injection are also sometimes used to treat the symptoms of low estrogen in young women who do not produce enough estrogen naturally. The estradiol valerate form of estrogen injection is also sometimes used to relieve the symptoms of certain types of prostate (a male reproductive organ) cancer. The conjugated estrogens form of estrogen injection is used to treat abnormal vaginal bleeding that a doctor has decided is caused only by a problem with the amounts of certain hormones in the body. Estrogen injection is in a class of medications called hormones. It works by replacing estrogen that is normally produced by the body.
Vitamin D - More Interactions
Vitamin D interacts with 694 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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In addition to being a clinical pharmacist specializing in pharmacotherapy, Dr. Brian Staiger is a registered herbalist through the American Herbalist Guild. He has combined his passion for pharmacy practice with the study of medical ethnobotany to improve patient care. Feel free to reach out about any of your herbal or medication questions!
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