Prevalence and type of drug-drug interactions involving ART in patients attending a specialist HIV outpatient clinic in Kampala, Uganda

Objectives

Scale-up of HIV services in sub-Saharan Africa has rapidly increased, necessitating evaluation of medication safety in these settings. Drug–drug interactions (DDIs) involving antiretrovirals (ARVs) in sub-Saharan Africa are poorly characterized. We evaluated the prevalence and type of ARV DDIs in Ugandan outpatients and identified the patients most at risk.

Methods

A total of 2000 consecutive patients receiving ARVs at the Infectious Diseases Institute, Kampala were studied. The most recent prescription for each patient was screened for clinically significant DDIs using www.hiv-druginteractions.org. Univariable and multivariable logistic regression were used to identify risk factors for DDIs. A screening tool was developed using significant risk factors and tested in a further 500 patients.

Results

Clinically significant DDIs were observed in 374 (18.7%) patients, with a total of 514 DDIs observed. Only 0.2% of DDIs involved a contraindicated combination. Comedications commonly associated with DDIs were antibiotics (4.8% of 2000 patients), anthelmintics (2.2%) and antifungals (3.5%). Patient age, gender, CD4 count and weight did not affect risk of DDIs. In multivariable analysis, the patient factors that independently increased risk of DDIs were two or more comedications (P < 0.0001), a PI-containing ARV regimen (P < 0.0001), use of an anti-infective (P < 0.0001) and WHO clinical stage 3–4 (P = 0.04). A scoring system based on having at least two of these risk factors identified between 75% and 90% of DDIs in a validation cohort.

Conclusions

Significant ARV DDIs occur at similar rates in resource-limited settings and developed countries; however, the comedications frequently causing DDIs differ. Development of tools that are relevant to particular settings should be a priority to assist with prevention and management of DDIs.

The clinical utility of HIV outpatient pharmacist prescreening to reduce medication error and assess adherence

Antiretroviral therapy (ART) is complex and has high propensity for medication error and drug-drug interactions (DDIs). We evaluated the clinical utility of pharmacist prescreening for DDIs, adherence to ART and medicines reconciliation prior to HIV outpatient appointments. A pharmacist took detailed medication histories and ART adherence assessments, then screened medication for DDIs. A template detailing current medication, potential DDIs and adherence was filed in the clinical notes and physicians were asked for structured feedback. Potential DDIs were observed in 58% of 200 patients, with 22 (9%) potential DDIs occurring with medication that was not previously recorded in the patients’ notes. Of 103 physician responses, 61.2% reported that the pharmacist consultation told them something they did not know, and pharmacist consultants led to change in management in 13.6% of cases. Pharmacist consultations were more likely to add benefit in patients taking two or more concomitant medications in addition to ART ( P = 0.0012).

Global patient safety and antiretroviral drug-drug interactions in the resource-limited setting

Scale-up of HIV treatment services may have contributed to an increase in functional health facilities available in resource-limited settings and an increase in patient use of facilities and retention in care. As more patients are reached with medicines, monitoring patient safety is increasingly important. Limited data from resource-limited settings suggest that medication error and antiretroviral drug-drug interactions may pose a significant risk to patient safety. Commonly cited causes of medication error in the developed world include the speed and complexity of the medication use cycle combined with inadequate systems and processes. In resource-limited settings, specific factors may contribute, such as inadequate human resources and high disease burden. Management of drug-drug interactions may be complicated by limited access to alternative medicines or laboratory monitoring. Improving patient safety by addressing the issue of antiretroviral drug-drug interactions has the potential not just to improve healthcare for individuals, but also to strengthen health systems and improve vital communication among healthcare providers and with regulatory agencies.