Drug–Drug Interactions in COPD Therapy: A Community Pharmacy Study ^†

Background:

Chronic obstructive pulmonary disease (COPD) patients frequently receive multiple concomitant drugs, raising the risk of drug–drug interactions (DDIs). We analyzed 107 COPD prescriptions (ICD-10 code J44.0–J44.9), evaluating demographics and DDI severity to identify the most common major interactions and their corresponding patient profiles.

Methods:

We conducted a retrospective study of prescriptions (ICD-10 codes J44.0–J44.9) dispensed over three months at a community pharmacy. For each prescription, we recorded the patient’s age, sex, comorbid diagnoses, and drugs. DDI assessments performed using Drugs.com categorize them as major, moderate, minor, or none [1]. Patients were stratified into six age groups (40–49, 50–59, 60–69, 70–79, 80–89, and >90 years). All procedures adhered to ethical standards and followed the guidelines for research involving human data.

Results and discussion:

The dataset included 107 prescriptions with ICD-10 codes J44.0–J44.9, of which 78 (72.9%) were for males and 29 (27.1%) were for females. The mean age was 66.9 ± 12.0 years (range: 43–92), with a median of 67 years. The age-group breakdown was as follows: 40–49 years, 10.3% (n = 11); 50–59 years, 18.7% (n = 20); 60–69 years, 23.4% (n = 25); 70–79 years, 30.8% (n = 33); 80–89 years, 15.0% (n = 16); and >90 years, 1.9% (n = 2). In total, 58 (54.2%) prescriptions showed no interactions, 33 (30.8%) had moderate interactions, 16 (15.0%) featured major interactions, and none exhibited minor interactions. Major DDIs were more frequent in males (14 of 16; 87.5%) versus females (2 of 16; 12.5%) and clustered in older age brackets: 80–89 years accounted for 6 of 16 (37.5%), and 60–69 years accounted for 1 of 16 (6.3%), with the remaining split equally between 40–49 years and 80–89 years for the female cases. The most frequent major DDIs were exclusively observed in males over 60 years of age: carvedilol–theophylline (two occurrences in males: one aged 60–69 and one aged 80–89), nebivolol–theophylline (two prescriptions, both for males aged 80–89), and simvastatin–amlodipine (two occurrences in males aged 80–89). In patients with COPD, theophylline is an add-on therapy when bronchodilator therapy does not satisfactorily control the disease. Family doctors, not pulmonologists, usually prescribe theophylline; it appears in 27 prescriptions, but managing its adverse effects and interactions can be challenging due to its narrow therapeutic index and the predominant hepatic CYP1A2 metabolism [2,3]. Combining theophylline with non-selective beta-blockers or high doses of beta-1-selective beta-blockers can produce severe bronchospasm due to the opposite pharmacological effects. Although beta-1-cardioselective beta-blockers do not generally inhibit the bronchodilator effect of beta-2-adrenergic agonists, they can still cause acute bronchospasm in COPD patients despite their relative selectivity for beta-1 receptors in cardiac tissues [4,5,6].

Conclusions:

Over half of COPD prescriptions demonstrated no DDIs; however, 15% exhibited major interactions, predominantly involving combinations of cardioactive and theophylline-based agents in older male patients. These preliminary results facilitate COPD patient phenotyping and personalized treatment based on demographic and pharmacotherapy profiles [5,7,8].