Clinically important drug-drug interactions in primary care

Interactions between selected over-the-counter drugs and food: clinical relevance and prevention

The use of medicines is associated with both therapeutic and adverse effects and interactions. In particular, interactions between drugs and food are common, and can either enhance the action of drugs or diminish their effect. Health professionals have a responsibility to screen for and educate patients about food-drug interactions, as well as to assist in decreasing their occurrence. The aim of this study was to identify any interactions present between food and selected over-the-counter (OTC) drugs. Sixty-five publications out of a potential 1112 found in the search were included in the study and among them 28 concerned painkillers, 6 - antihistamines, 4 - nasal decongestants, 10 were for proton pump inhibitors and for iron and 8 for sildenafil. Interactions between food and OTC drugs do exist. These drugs should not be taken regardless of the meal. Providing relevant information to the patient will increase drug safety and efficacy.

Ambulatory Medication Safety in Primary Care: A Systematic Review

PURPOSE

To review the literature on medication safety in primary care in the electronic health record era.

METHODS

Included studies measured rates and outcomes of medication safety in patients whose prescriptions were written in primary care clinics with electronic prescribing. Four investigators independently reviewed titles and analyzed abstracts with dual-reviewer review for eligibility, characteristics, and risk of bias.

RESULTS

Of 1464 articles identified, 56 met the inclusion criteria. Forty-three studies were noninterventional and 13 included an intervention. The majority of the studies (30) used their own definition of error. The most common outcomes were potentially inappropriate prescribing/medications (PIPs), adverse drug events (ADEs), and potential prescribing omissions (PPOs). Most of the studies only included high-risk subpopulations (39), usually older adults taking > 4 medications. The rate of PIPs varied widely (0.19% to 98.2%). The rate of ADEs was lower (0.47% to 14.7%). There was poor correlation of PIP and PPO with documented ADEs leading to physical harm.

CONCLUSIONS

This literature is limited by its inconsistent and highly variable outcomes. The majority of medication safety studies in primary care were in high-risk populations and measured potential harms rather than actual harms. Applying algorithms to primary care medication lists significantly overestimates rate of actual harms.

Influence of Renal Impairment and Genetic Subtypes on Warfarin Control in Japanese Patients

The genotypes of vitamin K epoxide reductase complex 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9) can influence therapeutic warfarin doses. Conversely, nongenetic factors, especially renal function, are associated with warfarin maintenance doses; however, the optimal algorithm for considering genes and renal dysfunction has not been established. This single-center prospective cohort study aimed to evaluate the factors affecting warfarin maintenance doses and develop pharmacogenetics-guided algorithms, including the factors of renal impairment and others. To commence, 176 outpatients who were prescribed warfarin for thromboembolic stroke prophylaxis in the stroke center, were enrolled. Patient characteristics, blood test results, dietary vitamin K intake, and CYP2C9 and VKORC1 (-1639G>A) genotypes were recorded. CYP2C9 and VKORC1 (-1639G>A) genotyping revealed that 80% of the patients had CYP2C9 *1/*1 and VKORC1 mutant AA genotypes. Multiple linear regression analysis demonstrated that the optimal pharmacogenetics-based model comprised age, body surface area, estimated glomerular filtration rate (eGFR), genotypes, vitamin K intake, aspartate aminotransferase levels, and alcohol intake. eGFR exercised a significant impact on the maintenance doses, as an increase in eGFR of 10 mL/min/1.73 m² escalated the warfarin maintenance dose by 0.6 mg. Reduced eGFR was related to lower warfarin maintenance doses, independent of VKORC1 and CYP2C9 genotypes in Japanese patients.