Introduction:
Adverse drug reactions (ADRs) remain a major challenge in specialised hospital units, where patients often present with complex illnesses and receive multiple medicines. Early identification and structured reporting are essential for preventing avoidable harm and improving therapeutic outcomes. This study examined the patterns, severity, causality, preventability, and outcomes of ADRs reported from specialised care units in a tertiary teaching hospital.

Methods:
A prospective cohort study was undertaken over three months in the intensive care settings of two specialised blocks within a tertiary hospital. Inpatients of all age groups were monitored for suspected ADRs following medicine administration. Data were collected using standardised ADR reporting forms adopted from the national pharmacovigilance system. Each ADR was assessed for causality using the WHO-UMC scale, severity using the Hartwig–Siegel scale, seriousness based on PvPI criteria, and preventability using the modified Schumock–Thornton method.

Results:
A total of 97 ADRs were identified. Adults accounted for most cases, with a balanced distribution between males and females. Probable ADRs formed the largest proportion (86.6%). Most reactions were mild and definitely preventable. Antibiotics were the most common drug class implicated, and skin-related hypersensitivity reactions were predominant. Almost all patients recovered fully following appropriate clinical management, including drug withdrawal or supportive treatment.

Conclusions:
The findings highlight the need for strengthened ADR monitoring in specialised units, with a particular focus on antimicrobial use and hypersensitivity reactions. Enhanced clinical pharmacist involvement and structured reporting systems may improve medicine safety and patient outcomes.

Keywords: Adverse Drug Reactions, Intensive Care, Pharmacovigilance, Causality Assessment, Patient Safety