Schizophrenia is a debilitating mental illness that affects 21 million people worldwide and 1 % of the population in Pakistan. The use of Typical Antipsychotic Drugs (TAPDs) has declined due to the discovery of AAPDs in 1990s, since TAPDs are associated with extrapyramidal side effects, the major reason of non-compliance. Antipsychotic Drugs (APDs) including haloperidol, olanzapine, risperidone, quetiapine and aripiprazole have been widely prescribed to treat various psychiatric disorders, including schizophrenia and other affective disorders. However, abnormal glucose metabolism and weight gain have been reported with AAPDs that can lead to insulin-resistance and type 2 diabetes mellitus, but no consensus has been developed regarding mechanisms of these toxicities. There are contradictory reports on these alarming events employing different experimental models, methodologies and criteria. Various mechanisms have, however, been elucidated, reporting the interference of AAPDs with muscarinic receptors in pancreas which deteriorates insulin release from beta cells and histamine receptors in inducing weight gain which itself is a risk factor for diabetes, insulin resistance and other cardiovascular incidents. No studies exist that report the direct effect of these drugs on the architecture of the pancreas except two studies which have reported the effects of olanzapine and risperidone on the architecture of kidneys and liver in rats. Similarly, there are no reports on the impact of these drugs on Pakistani population. Different biochemical parameters are mandatory to be studied in the same group which are lacking in the internationally reported studies. We, therefore, designed this study to explore mechanisms of these toxicities, both in animals and humans. The study was completed in two phases, that is, the preclinical vi phase and the clinical phase. The purpose of the preclinical phase was to screen the most widely reported drugs (olanzapine and risperidone) for any changes in the architecture of the pancreas. In clinical phase of the study, APDs-naïve patients with first episode psychosis visiting outpatient department (OPD) of the Medical Teaching Institution, Khyber Teaching Hospital, Peshawar and a Psychiatric Clinic were recruited for study. In this phase, the patients with first episode psychosis were screened for whether these alarming events are associated with APDs, the disease itself or both. In the preclinical phase of the study, olanzapine was administered orally in an escalating dose manner for 14 weeks. Olanzapine was administered in a dose of 5 mg/kg/d for first 8 weeks, 10 mg/kg/d for next 4 weeks and 15 mg/kg/d for the last 2 weeks, as used and proposed by various studies. Risperidone was administered orally for three weeks in a dose of 2.5 mg/kg/d employing the reported methods. Controls were run in parallel receiving acidified saline (vehicle used in drug formulation) only. The animals had access to diet in an amount not more than 20g/12h. The animals were sacrificed, blood samples collected and tissues isolated for histological assessment. The blood samples were screened for serum levels of alanine transaminase (ALT), aspartate transaminase (AST), amylase and lipase. Body weight and Random blood Sugar was measured on weekly basis. Statistical analysis of the olanzapine treated group revealed significant elevation in the blood glucose level in the 8th week to 14th weeks of the experiment (P <0.05, P <0.01, P < 0.001) and significant rise in the level of amylase (P <0.05) and lipase (P < 0.001) at the end of the experiment. Serum ALT and AST remained unaffected (P > 0.05). Significant vii percent weight gain (P <0.05, P <0.01, P < 0.001) was noticed in controls as compared to drug treated group from 5th week to 14th weeks of the experiment depicting weight loss in the drug treated groups. Histological assessment of the pancreas of olanzapine treated group revealed nodular appearance, derangement of beta cells and fibrotic growth. Liver remained unaffected while the kidneys showed mild to moderate focal increase in glomerular cellularity and cellular proliferation. A few glomerular capsules with negligible basement membranes were also identified. Statistical analysis of risperidone group revealed significant elevation in the level of amylase (P<0.001) only. Histological assessment of risperidone treated group showed derangement of the beta cells of the pancreas, however, the parenchyma of liver and the architecture of the kidneys was not deteriorated. In clinical phase of the study, antipsychotic drugs-naïve non-diabetic patients (n=57) with first episode psychosis admitted to psychiatry unit or who visited OPD, Khyber Teaching Hospital, Peshawar, K.P, Pakistan or Psychiatry Clinic, Peshawar, were included in this study. Patients of either gender with no previous history of antipsychotics aging not less than 18 years were part of the study. The patients on olanzapine, quetiapine, risperidone, aripiprazole and haloperidol monotherapies were grouped as OLAN (n=8), QUET (n=8), RISP (n=8), ARIP (n=8) and HAL (n=8) respectively while patients receiving combination of olanzapine with escitalopram, a single dose of parenteral diazepam and a single dose of parenteral haloperidol were grouped as OLEDH (n=8). Six patients failed to report for follow-up and three were dropped due to non-compliance. The patients were followed for an average time period of 30 to 45 days. viii Statistical analysis revealed significant elevation in the level of cholesterol in aripiprazole treated group (ARIP, n=8, P<0.001) when compared to their pretreatment levels (n=8). The level of alanine and aspartate transaminases was also significantly raised in haloperidol treated group (HAL, n=8, P<0.001) in comparison to their pretreatment level. The level of amylase was significantly elevated in combination group (OLEDH, n=8, P<0.01), olanzapine (OLAN, n=8, P<0.01) and aripiprazole (ARIP, n=8,P<0.05) treated groups while that of lipase was significantly elevated in combination group (OLEDH, n=8,P<0.05) and risperidone (RISP, n=8, P<0.01) treated group. The level of insulin, random blood glucose and c-peptide remained unchanged (P>0.05) in all of the treated groups. Similarly, % body weight, % beta function and Insulin Resistance (IR) were also not changed significantly (P>0.05). In order to preclude the involvement of predisposing factors supposed to be associated with disturbance of insulin and glucose levels, it was observed that 21.05 % of the total patients’ population presented abnormally elevated insulin values before exposure to APDs when compared with reference values, which helped in the conclusion that there are certain other factors other than APDs which might be the culprits in rendering the insulin levels elevated. Similarly, 22.81 % (13/57 patients), 8.77 % (5/57 patients), 21.05 % (12/57) of the total patients’ population were found abusers of cannabis/charas, tobacco and/or oral snuff (Naswar) respectively. Thus 38.46 % (5/13 patients) among the cannabis/charas abusers, 40 % (2/5 patients) with habit of smoking tobacco and 33.33 % (4/12 patients) with the habit of using snuff (Naswar, a semisolid mass of tobacco leaves kept in the buccal cavity) were presented with abnormally elevated insulin levels. Dramatically, 10 patients were found whose level decreased from abnormal to normal ix after the commencement of APD treatment, but the same number of patients was found whose insulin level elevated from normal to abnormal with the APD treatment. On the other hand, 40.74 % (11/27 patients) of the non-abusers showed elevated insulin levels. Only 3.51 % (2/8 patients), 7.02 % (4/8 patients), 3.51 % (2 patients), 0 % (0/8 patients), 7.02 % (4/8 patients) and 0 % (0/8 patients) of the combination (OLEDH), quetiapine (QUET), olanzapine (OLAN), risperidone (RISP), aripiprazole (ARIP) and haloperidol (HAL) groups respectively showed elevated insulin levels after exposure to their respective treatments. Similarly, 14.03 % of the total patients’ population (non-diabetic) showed elevated random blood sugar (RBS) before any exposure to antipsychotics. Among the drug dependents, 38.46 % (5/13 patients) of cannabis/charas abusers, 40 % (2/5 patients) with habit of smoking tobacco and 41.67 % (5/12 patients) with the habit of using snuff (Naswar) were presented with abnormally elevated RBS levels before exposure to APD(s). Interestingly, the level of RBS decreased from abnormal to normal in 10.53 %, while elevated from normal to abnormal in 8.77% of the total patients’ population after treatment with respective APD(s). Out of the non-abusers (27/57), 22.22% (6/27 patients) were found with elevated blood sugar before commencement of their respective treatments. Only, 12.5 % (1/8 patients) of the combination, QUET and RISP groups, 25 % (2/8 patients) of the OLAN and ARIP groups and 0% (0/8 patients) of the HAL group were shown with elevated RBS levels after their respective treatments. In conclusion, it was shown that olanzapine and risperidone bring damage to the pancreatic architecture in animals. The same drugs either changed lipase or amylase in rats that could be an alarming sign of pancreatic damage. Olanzapine was proved mild to x moderately toxic to kidneys, while risperidone remained safe. Both of the drugs were safe for liver in rats as well. In humans, the level of cholesterol was elevated with aripiprazole. Haloperidol caused elevation of both ALT and AST, which is the sign of hepatotoxicity. No muscle damage was seen since the level of CPK remained unaffected. We found that the toxicities associated with olanzapine and risperidone might be lessened/delayed if the diet provided is intervened, since our dietary intervention (restricted amount, 20g/12h) has delayed the already reported toxicities for weeks. Based on our study and the published reports, it is suggested to monitor body weight, blood glucose, liver function, renal function, lipid profile and amylase and/or lipase level(s) in patients undergoing therapy with APDs. The patients may be provided restricted diet to possibly prevent or delay the APDs-associated unwanted concerns. It is also concluded that it is not only APDs but certain other factors including psychosis, opium, cannabis, cigarette and snuff (naswar) might have involvement in causing metabolic abnormalities, the conclusion based on the fact that some patients (non-diabetic) were observed with elevated insulin and/or blood glucose levels which was rendered normalized after the use of an APD, while other patients were noticed whose level of insulin and blood glucose showed elevation with APDs treatment." xml:lang="en_US