BackgroundAcute coronary syndrome (ACS) is a leading cause of mortality and morbidity in Qatar and globally.AimThe primary objective of the study was to evaluate the effectiveness of a structured clinical pharmacist-delivered intervention on all-cause hospitalizations and cardiac-related readmissions in patients with ACS.MethodA prospective quasi-experimental study was conducted at Heart Hospital in Qatar. Discharged ACS patients were allocated to one of three study arms: (1) an intervention group (received a structured clinical pharmacist-delivered medication reconciliation and counselling at discharge, and two follow-up sessions at 4 weeks and 8 weeks post-discharge), (2) a usual care group (received the general usual care at discharge by clinical pharmacists) or, (3) a control group (discharged during weekends or after clinical pharmacists' working hours). Follow-up sessions for the intervention group were designed to re-educate and counsel patients about their medications, remind them about the importance of medication adherence, and answer any questions they may have. At the hospital, patients were allocated into one of the three groups based on intrinsic and natural allocation procedures. Recruitment of patients took place between March 2016 and December 2017. Data were analyzed based on intention-to-treat principles.ResultsThree hundred seventy-three patients were enrolled in the study (intervention = 111, usual care = 120, control = 142). Unadjusted results showed that the odds of 6-month all-cause hospitalizations were significantly higher among the usual care (OR 2.034; 95% CI: 1.103–3.748,p= 0.023) and the control arms (OR 2.704; 95% CI: 1.456–5.022,p= 0.002) when compared to the intervention arm. Similarly, patients in the usual care arm (OR 2.304; 95% CI: 1.122–4.730,p= 0.023) and the control arm (OR 3.678; 95% CI: 1.802–7.506,p≤ 0.001) had greater likelihood of cardiac-related readmissions at 6 months. After adjustment, these reductions were only significant for cardiac-related readmissions between control and intervention groups (OR 2.428; 95% CI: 1.116–5.282,p= 0.025).ConclusionThis study demonstrated the impact of a structured intervention by clinical pharmacists on cardiac-related readmissions at 6 months post-discharge in patients post-ACS. The impact of the intervention on all-cause hospitalization was not significant after adjustment for potential confounders. Large cost‐effective studies are required to determine the sustained impact of structured clinical pharmacist-provided interventions in ACS setting.Trial registrationClinical Trials: NCT02648243 Registration date: January 7, 2016.