OBJECTIVES: The aim of this study is to determine the rate and pattern of drug related problems (DRPs) associated with narrow therapeutic index drugs (NTIs).

METHODS: The patients who are receiving at least one NTI and admitted to the wards of General Medicine, Cardiology and Neurology were enrolled with consent and followed till their discharge. The list of NTIDs was prepared through literature review. The Helper and Strand’s classification of Drug Related Problems (DRPs) was adapted, and the eligible patients’ case sheets were reviewed for DRPs. Adverse Drug Reactions (ADRs) were assessed for causality using the WHO-UMC Probability scale, and severity by Hartwig’s. The data obtained were assessed categorically and represented as [n (%)].

RESULTS: Following interim analysis, a total of 117 DRPs were identified amongst 52 patients wherein, [38 (73.08%)] were males and [14 (26.92%)] were females. Most frequently recorded DRPs were drug-drug interactions [58 (49.57%)], followed by Sub-therapeutic dosing [27 (23.08%)], ADRs [13 (11%)], Untreated indication & Improper drug selection [8 (7%)]. The causality assessment for majority of identified ADRs were classified as probable [10 (77%)] and [12 (92.31%)] ADRs were classified as moderate in severity nature. Insulin and Carbamazepine were commonly implicated and [12 (92%)] ADRs resulted in extended hospitalization and [7 (53%)] were managed specifically and all were recovered with no sequel. Majority experienced pharmacokinetic interactions [27 (46.55%)], wherein 44% were associated with altered absorption and, 48% were altered metabolism. Amongst pharmacodynamic interactions 71% were synergistic. Acceptance rate of pharmacist intervention is 100%.

CONCLUSIONS: NTI drugs demand low margin of error and any DRP would result in extended stay in hospital. Early identification and remedial action of the DRPs will reduce the risk of drug induced morbidity and mortality.