Abstract
Background: Antipsychotic drugs are commonly used pharmacological agents, which have varied adverse reactions. There is a need to investigate the prevalence of these adverse reactions due to the implications for clinical practice and research. Studies on the prevalence of these adverse reactions are few, especially from Indian subcontinent.

Aim and Objectives: The objectives of this study were as follows: (i) To investigate the drug emergent adverse drug reactions (ADRs) in patients who are on antipsychotic drugs and (ii) to study the severity of ADRs due to antipsychotic agents and association between the adverse reaction and the suspected drug.

Materials and Methods: This is a prospective observational study, in which 99 patients out of 120 patients suffering with mental illness were enrolled. Base-line investigations such as CBP, ESR, serum creatinine, serum electrolytes, serum cholesterol, serum prolactin, and FBS (fasting blood sugar) were performed and the same were repeated at 1st month and 3rd month and checked for any abnormality. Any suspected ADRs were noted after 1 month and 3 months in patients after starting the treatment with antipsychotic drugs. The patients were assessed with semi-structured interview, the patient rated side effects scale (LUNSERS), and an adverse drug probability scale (Naranjo probability scale). The results were analyzed with SPSS software. The ADRs in patients were also compared between in-patients and out-patients.

Results: The atypical drugs particularly risperidone and olanzapine were commonly prescribed for the patients, than typical antipsychotic drugs such as haloperidol. Out of the 99 patients, risperidone was prescribed for 56.6% of patients, olanzapine was prescribed for 40.4% patients, amisulpride was prescribed for 1% of patient, and haloperidol for 2% of patients. About 79% of the patients under study developed ADRs within a month and 21% developed after a month. These drugs were given twice-daily dosage regimen for 89.9% of the patients than once daily dosage regimen, which is 10.1%. Forty-one were in-patients and 58 patients were out-patients. Among the in-patients, risperidone drug was given for 28 (68.3%) patients, olanzapine was given for 11 (26.8%) patients, amisulpride for 1 (2.4%) patient, and haloperidol for 1 (2.4%) patients. The most common ADRs in in-patients was EPS (90.24%) with a statistically significant P < 0.0001. In out-patients, risperidone was prescribed for 28 (48.3%) patients, olanzapine was given for 29 (50%) patients, and haloperidol for 1 (1.7%) patient. The most common ADR among out-patients was sedation (82.75%) with P = 0.0001, which is statistically significant. The ADRs were “significant” according to LUNSERS overall score and are “probable” according to Naranjo’s probability assessment scale.

Conclusion: The most common antipsychotic drugs used were risperidone and olanzapine. The common drug emergent adverse reactions were EPS and sedation when the drugs were prescribed twice-daily dosage regimen. The time taken for these ADRs to emerge is ≤1 month. The ADRs are significant according to LUNSERS and probable due to suspected drug according to Naranjo’s probability assessment scale. In comparison between in-patients and out-patients, EPS was found more among in-patients and sedation in out-patients. Depending on the intensity of the ADRs, the antipsychotics drug dosage was reduced or drug changed or another was added to combat the ADRs.

Key words: Antipsychotic agents; Adverse drug reactions; Extrapyramidal symptoms; LUNSERS; Naranjo probability scale