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Drug-drug interactions with Over-the-Counter drugs

Global DDI Solution

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Population aging is accompanied by a higher prevalence of comorbidities. For those comorbidities, different drugs are used, which leads to polypharmacy. With the use of many drugs, the risk of Drug-Drug interactions (DDIs) increases, which can cause treatment failure or undesired adverse effects.

For certain patient groups (e.g. HIV or cancer patients) use of over-the-counter (OTC) drugs and other substances (e.g. vitamins/mineral supplements, anabolic steroids, recreational drugs) is increasingly common. These OTC drugs can also be perpetrators or victims of DDIs. Pharmacokinetic studies of OTC drugs combined with other drugs are limited. In addition, the use of OTC drugs is not always known to health professionals, which makes it difficult to collect and publish DDI cases with OTC drugs.

Mainly, pharmacokinetic studies for registration of prescribed drugs are added to the product information of the drug. Case reports and studies from practice are minimally included in these documents.

This study looked at reported cases of real-world DDIs on between HIV medication and co-medication, including OTC drugs. This website is an open-access platform for healthcare professionals for concise descriptions of real-world clinical cases, specifically involving antiretrovirals and their associated clinical harms.

Between March 2019 and May 2023, a total of 139 cases were reported, of which 27 cases with OTC. 11 cases with mineral supplements (calcium and magnesium) were reported, 8 cases with herbals, 4 cases with weight loss drugs, 3 cases with anabolic steroids and 1 case with recreational drug (MDMA). Of these cases, 21 cases had unwanted outcomes (78%). 17 cases of cases with unwanted outcomes had a loss of ARV efficacy, defined as detectable plasma HIV-RNA previously virologically suppressed individuals. In these cases, 10 cases of mineral supplements were involved, primarily calcium and magnesium.

It is often underestimated how much impact mineral supplements can have on prescribed medication. Therefore, it is important to educate patients about potential interactions with OTC drugs, as many individuals may not perceive minerals, herbal supplements, recreational drugs, or other OTC drugs as traditional medications and they may not be aware of possible DDIs.

19.4% of the cases involved OTC drugs which means that in addition to ARVs, this may also be a common problem with other drugs, such as cancer medications, antibiotics and antifungal agents. Therefore, it is important to document real-world cases to bridge knowledge gaps and increase the quality of care. 20. For the databases of the DDI Manager, real-world outcomes of DDIs are examined, including articles and case reports. This allows a complete picture of potential DDIs per drug.

See for more information the article: Outcomes of Drug Interactions Between Antiretrovirals and Co-Medications, Including Over-the-Counter Drugs: A Real-World Study