Identification and Communication Approaches to Drug and Dietary Supplement Interactions

SupplementsVitamin and Supplements Guide for Pharmacists
Volume 1
Issue 1

Pharmacists are ideally positioned to educate patients on which supplements to take with their medications.

Dietary supplement use is common among adults in the United States. According to the results of the 2019 Council for Responsible Nutrition Consumer Survey on Dietary Supplements, 77% of Americans reported consuming dietary supplements.1 Data on prescription drug use from the National Center for Health Statistics (2013-2016) indicated that about 48% of Americans have used at least 1 prescription medication in the past 30 days, and research has shown that approximately one-third of American adults have reported taking dietary supplements while using prescription medications.2,3 Although drug interactions exist among many prescription medications and dietary supplements, certain nutrients may be beneficial for patients, particularly while taking certain medications, and as frontline providers, pharmacists are ideally positioned to educate patients on which supplements to take with their medications.1,4

The following patient cases provide examples of potential dietary supplement and medication interactions along with counseling approaches and suggested supplements that could be used in such scenarios.

Case Study #1

An Adult Woman Picks Up Birth Control Medication and Would Like to Purchase a St John’s Wort Supplement

A 35-year-old woman arrived at the pharmacy window to pick up her birth control medication (norethindrone acetate + ethinyl estradiol + ferrous fumarate). She also brought a bottle of St John’s wort to the window to add to her purchase. After prompting from the pharmacist, the patient stated she was taking the St John’s wort for mild depression and stress support.

What concerns might exist regarding her current birth control medication and this supplement?


The pharmacy technician who helped the woman with her medication pickup knew to notify the pharmacist of any other medications or supplements the patient was taking. The pharmacist then confirmed with the patient that she was not taking any other dietary supplements. He then completed an updated drug utilization review (DUR) with the new information provided.

The pharmacist was then able to counsel the patient on the potential for drug—supplement interactions. He explained that St John’s wort can interact with the birth control medication the patient is currently prescribed, decreasing the birth control medication’s effectiveness by increasing its breakdown. The patient stated that she previously received a diagnosis of mild depression but had not followed up with her regular primary care doctor after the initial diagnosis and had not used any medications or other therapy.

The pharmacist then recommended that she not initiate the St John’s wort until speaking with her primary care provider or psychiatrist because of the potential interaction.5 The pharmacist advised the patient that alternative prescription options, as well as other therapies, could treat depression while not decreasing the effectiveness of her birth control. He offered to provide recommendations to her health care provider if it was determined that a medication option was warranted. The pharmacist also recommended several supplements to ensure that she receives the nutritive support she may need while taking birth control therapy.6

After the pharmacist provided the information, the patient appreciated that he took the time to alert her to the potential interaction and offered to speak with her health care provider about alternative options, if necessary. The patient was receptive to following up with her primary care provider. The pharmacist contacted the patient by phone a few days after their discussion; she had seen her primary care provider, and they had determined she would try counseling to help her cope with her mild depression and stress, without initiating prescription medication at this time. Because of the recommendations made by her pharmacist and the subsequent discussion with her prescriber, she also initiated supplements to reach the total recommended daily value of folic acid, magnesium, and vitamin B6, as these nutrients may be depleted after chronic use of birth control.7,8

Case Study #2

An Elderly Patient Prescribed Digoxin Inquires About Hawthorn Supplements

A 75-year-old man approached the pharmacy drop-off window with a prescription for digoxin and requested to speak with the pharmacist about a hawthorn supplement he also brought to the counter.

What concerns might exist regarding digoxin and this supplement?


The patient explained to the pharmacist that his wife had read an article online saying that hawthorn could be helpful for patients with heart failure like himself. Because the pharmacist was not familiar with the hawthorn supplement, she consulted an online medication profile and drug interaction checker. She also reviewed the patient’s comprehensive medication list in his patient profile in the pharmacy fulfilment system (table) and confirmed with the patient that the list was current.

The online medication profile and drug interaction checker confirmed that hawthorn may enhance the activity of digoxin, which is a medication with an already-narrow therapeutic index. The pharmacist explained to the patient that hawthorn use could potentially cause digoxin to reach toxic levels in his body, and so hawthorn would be emphatically not recommended. Further, the pharmacist told him that his chronic digoxin therapy could possibly deplete his nutritional stores of calcium, magnesium, and potassium. She suggested supplement dosing to be sure he got the total daily recommended values.7,8

The patient was surprised by this information. He was unaware that supplements could interact with his prescription medications, and he thanked the pharmacist for alerting him. The pharmacist advised the patient to always inform health care providers of any herbal or other supplements he takes, or might be interested in taking, to help prevent future drug interactions.


Pharmacists can meaningfully impact the prevention of drug— supplement interactions and the complications that interactions may cause. As frontline health care providers, pharmacists are ideally positioned to provide guidance and education when situations like the ones described above occur. They can remind patients and/or their caregivers about the importance of alerting their health care providers to any supplements they take. Proper education of the entire pharmacy staff to check for missing information or missing medications in a patient profile can help to provide comprehensive care and ensure the best patient outcomes. This can be achieved through systematic approaches—for instance, during all medication pickups, inquiring about allergies and about medications and herbal supplements that may not be on file. Documenting this information will make the patient’s profile more complete and will make future DURs more efficient.

JAY HIGHLAND, PHARMD, is a patient care pharmacist and residency coordinator at Jewel-Osco Pharmacy in Chicago, Illinois.


  • Dietary supplement use reaches all time high. Council on Responsible Nutrition website. Published September 30, 2019. Accessed March 26, 2020.
  • Therapeutic drug use. CDC website. Reviewed January 19, 2017. Accessed March 1, 2020.
  • Farina EK, Austin KG, Lieberman HR. Concomitant dietary supplement and prescription medication use is prevalent among US adults with doctor-informed medical conditions. J Acad Nutr Diet. 2014;114(11):1784-1790.e2. doi: 10.1016/j.jand.2014.01.016.
  • Meletis CD, Zabriskie N. Common nutrient depletions caused by pharmaceuticals. Alt Comp Ther. 2007;13(1):10-17. doi: 10.1089/act.2006.13102.
  • Horn JR, Hansten PD. Oral contraceptives and St. John’s wort. Pharmacy Times® website. Published February 2, 2018. Accessed March 2, 2020.
  • Prescott JD, Drake VJ, Stevens JF. Medications and micronutrients: identifying clinically relevant interactions and addressing nutritional needs. J Pharm Technol. 2018;34(5):216-230. doi: 10.1177/8755122518780742.
  • Weitzel KW, Goode J-VR. Constipation. In: Krinsky DL, Ferreri SP, Hemstreet B, et al. Handbook of Nonprescription Drugs: An Interactive Approach to Self-Care. 19th ed. New York, NY: Humana Press; 2017:chapter 15. doi: 10.21019/9781582122656.ch15.
  • Food labeling: revision of the Nutrition and Supplement Facts Labels: guidance for industry — small entity compliance guide. FDA website. media/134505/download. Updated February 3, 2020. Accessed March 23, 2020.

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