Psychotropic Medicines and Metabolic Monitoring

Psychotropic medicines are central to the management of many mental health conditions. However, their use is associated with clinically significant metabolic adverse effects, including weight gain, dyslipidaemia, impaired glucose tolerance and type 2 diabetes, hypertension, and ultimately increased cardiovascular risk. These adverse effects are commonly associated with antipsychotics, although some antidepressants and mood stabilisers may also contribute.

Monitoring of metabolic adverse effects is not always optimal, which may contribute to the substantial morbidity and premature mortality in people living with severe mental illness.

Why metabolic monitoring matters

People with severe mental illness already experience poorer physical health outcomes than the general population.

An Australian report found that people living with mental illness are:

• Twice as likely to have cardiovascular disease;
• Twice as likely to have respiratory disease;
• Twice as likely to have metabolic syndrome;
• Twice as likely to have diabetes;
• Twice as likely to have osteoporosis;
• 65% more likely to smoke; and
• Six times more likely to have dental problems.

This population also accounts for around one third of all avoidable deaths. People living with severe mental illness are particularly at risk and are estimated to die between 14 and 23 years earlier than the general population.

Cardiovascular disease is a leading cause of premature death in this population. People with serious mental illness are more likely to have risk factors, such as smoking and poor diet. However, psychotropic medicines can further exacerbate this risk through multiple mechanisms, including:

• Weight gain (via increased appetite, reduced satiety, sedation-related inactivity);
• Reduced insulin sensitivity;
• Dyslipidaemia; and
• Hypertension.

Some studies have found that around 40% of people with chronic schizophrenia meet the criteria for metabolic syndrome.

Antipsychotics and relative metabolic risk

While all antipsychotics may contribute to metabolic abnormalities, the risk differs significantly between agents. Clozapine and olanzapine are considered high risk, while chlorpromazine is considered medium to high risk. It may be appropriate to avoid these agents in patients who are overweight, at high risk of cardiovascular disease, or have a family history of diabetes.

Antipsychotics associated with a medium risk include quetiapine, risperidone, and paliperidone. Asenapine, aripiprazole, brexpiprazole, cariprazine, haloperidol, lurasidone, and ziprasidone are considered low risk, although metabolic adverse effects can still occur.

Significant weight gain can occur within 6-8 weeks of initiating an antipsychotic, and early weight gain may be a predictor of long-term weight gain. Weight gain may be the most visible sign of metabolic disturbances and is often the most concerning for patients. However, it is important that weight is not the only focus of monitoring.

Dyslipidaemia and impaired glucose tolerance can develop even with minimal weight change, particularly in people with pre‑existing risk factors. Therefore, normal weight does not necessarily equal low cardiometabolic risk. Routine laboratory monitoring is essential, even when weight appears stable.

The potential for metabolic effects to develop early highlights the importance of baseline assessment and early follow-up.

Baseline assessment

Baseline data should be documented so that early changes can be identified. The Therapeutic Guidelines recommend assessment of the following parameters prior to initiating a psychotropic:

• Blood pressure and heart rate
• Weight, waist circumference and body mass index (BMI)
• Blood glucose and glycated haemoglobin (HbA1c) concentration
• Lipid concentrations, including triglycerides
• Level of physical activity
• Movement (involuntary or voluntary)
• Full blood count
• Blood prolactin concentration
• Electrocardiogram (as many antipsychotics can prolong the QT-interval).

Waist circumference is particularly important, as it may identify central adiposity even when weight or BMI fall within a healthy range.

Ongoing monitoring

Metabolic abnormalities often develop soon after antipsychotic initiation or dose escalation and guidelines emphasise the importance of early follow‑up. The Therapeutic Guidelines recommend monitoring of weight, waist circumference and BMI at 1 month, 2 months, 3 months, and 6 months after starting treatment, and every 6 months thereafter. Fasting blood glucose and HbA1c should be measured at 3 months and 6 months after initiating therapy and every 6 months thereafter. It is also recommended to measure fasting lipids every 6 months.

Clozapine requires especially close metabolic and physical health surveillance in addition to mandatory haematological monitoring.

Metabolic risk persists throughout treatment and may accumulate over time. Therefore, monitoring must continue long term. Transitions of care, such as discharge from inpatient units or changes between prescribers, are high‑risk points where monitoring responsibility can be lost.

Addressing abnormal results

Abnormal findings should trigger timely intervention, which may include lifestyle support or adjustment of psychotropic therapy.

Weight gain is often considered clinically significant when it increases by 7% or more from baseline. Lifestyle interventions are the first-line options and should be tailored to the patient. Studies suggest that a weight loss of at least 5% of body weight is associated with reduced cardiovascular risk and mortality.

A review of all other concurrent medications should be undertaken to identify any other drugs that may be contributing to the metabolic abnormalities. For example, hyperglycaemia is a common adverse effect of glucocorticoids, and weight gain can occur with the antiepileptics valproate and carbamazepine.

In some cases, switching to an antipsychotic with a lower metabolic risk profile may be considered. However, this must be carefully weighed against the risk of psychiatric destabilisation.

Where lifestyle interventions are not effective and adjusting antipsychotic therapy is either ineffective or inappropriate, metformin may be considered to treat antipsychotic-associated weight gain. Studies in patients with schizophrenia or schizoaffective disorder found a mean weight loss of 3.27kg (95% CI: −4.66 to −1.89, p < 0.001) and a reduction in BMI of −1.13 kg/m² (95% CI: −1.61 to −0.66). Additional benefits may include improved insulin sensitivity, reduced hepatic glucose production, and improved peripheral glucose uptake.

Pharmacological treatment may also be required for established dyslipidaemia, hypertension, or diabetes, in line with standard clinical guidelines.

Summary

Metabolic monitoring is a core safety requirement for patients receiving psychotropic medicines, particularly antipsychotics. Baseline assessment, early follow‑up, and long‑term monitoring is required to ensure the safe use of these medicines.