Drug–Drug Interactions With Over-The-Counter Medicines: Mind the Unprescribed

Abstract

Background:This review provides a summary of the currently available clinical data on drug–drug interactions (DDIs) involving over-the-counter (OTC) medicines. It aims to educate and increase awareness among health care providers and to support decisions in daily practice.Methods:An extensive literature search was performed using bibliographic databases available through PubMed.gov. An initial structured search was performed using the keywords “drug-drug-interaction AND (over-the-counter OR OTC),” without further restrictions except for the language. The initial results were screened for all described DDIs involving OTC drugs, and further information was gathered specifically on these drugs using dedicated database searches and references found in the bibliography from the initial hits.Results:From more than 1200 initial hits (1972–June 2021), 408 relevant publications were screened for DDIs involving OTC drugs, leading to 2 major findings: first, certain types of drug regimens are more prone to DDIs or have more serious DDI-related consequences, such as antiretroviral, anti-infective, and oral anticancer therapies. Second, although most DDIs involve OTC drugs as the perpetrators, some prescription drugs (statins or phosphodiesterase-5 inhibitors) that currently have OTC status can be identified as the victims in DDIs. The following groups were identified to be frequently involved in DDIs: nonsteroidal anti-inflammatory drugs, food supplements, antacids, proton-pump inhibitors, H2 antihistamines, laxatives, antidiarrheal drugs, and herbal drugs.Conclusions:The most significant finding was the lack of high-quality evidence for commonly acknowledged interactions. High-quality interaction studies involving different phenotypes in drug metabolism (cytochrome P450) and distribution (transporters) are urgently needed. This should include modern and critical drugs, such as oral anticancer medications and direct oral anticoagulants.

Unprescribed and unnoticed: Retrospective chart review of adverse events of interactions between antidepressants and over-the-counter drugs

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Screening for severe drug-drug interactions in patients with multiple sclerosis: A comparison of three drug interaction databases

“…In this Frontiers in Pharmacology frontiersin.org effort, the physicians should not only pay attention to the medications they prescribed, but should also place these in a critical context with the medications prescribed by physicians from other specialties. When checking for pDDIs, the use of OTC drugs should not be neglected (Scherf-Clavel, 2022) as, according to our previous study, about one in five pDDIs is related to OTC medicines in patients with MS (Bachmann et al, 2022). If a clinically relevant pDDI is identified, there are various options for dealing with it.…”

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“…Our results show that many patients take OTC drugs, and analgesics are the most common ones. These are highly potent drugs which are also commonly prescribed and can cause DRPs such as side effects and drug interactions [ 29 , 30 ]. OTC drugs will not be included in the National shared medication list in the beginning, but this should be considered in the future along with medications administered in the hospitals.…”