Chlorpromazine, the first antipsychotic ever developed, carries a wide range of side effects that touch nearly every organ system. Because it blocks dopamine receptors broadly rather than selectively, and because it also acts on histamine, serotonin, and acetylcholine receptors, its side-effect profile is broader and often more burdensome than that of newer antipsychotics. Some effects, like sedation and dry mouth, are merely annoying; others, like involuntary movement disorders or a rare syndrome of extreme rigidity and fever, can be disabling or life-threatening.
How Dopamine Blockade Drives the Most Recognizable Side Effects
Chlorpromazine works primarily by blocking dopamine receptors in the brain. Research dating back to the early 1970s showed that chlorpromazine directly antagonizes dopamine’s effects on neurons in the putamen, a brain region involved in movement control.1Brain Research. Dopamine receptor blockade — A central action of chlorpromazine on striatal neurones That same blockade produces the drug’s therapeutic effect against psychotic symptoms, but it also explains why movement-related side effects are so common. When dopamine signaling in the brain’s motor circuits gets suppressed too aggressively, you get symptoms that look a lot like Parkinson’s disease.
This is the core trade-off with chlorpromazine and older antipsychotics in general. The dopamine pathways that go haywire in psychosis overlap with the pathways that control voluntary movement, hormone release, and reward. Blocking dopamine in one pathway to treat psychosis means you inevitably disrupt the others.
Drug-Induced Parkinsonism and Akathisia
The most common neurological side effects people notice early in treatment are stiffness, slowness, tremor, and a loss of facial expression, collectively called drug-induced parkinsonism. The textbook description is bilateral and symmetrical stiffness without a resting tremor, but in practice about half of people with drug-induced parkinsonism show asymmetric symptoms and do have a resting tremor, making it hard to distinguish from actual Parkinson’s disease.2PubMed Central. Drug-induced parkinsonism The key difference is timing: drug-induced parkinsonism develops after starting or increasing the medication, and it usually improves when the dose is lowered or the drug is stopped.
Akathisia is a separate and deeply unpleasant side effect: an inner restlessness that makes sitting still feel almost impossible. People describe it as an urge to pace, shift weight, or rock back and forth. Higher chlorpromazine doses raise the risk. One study found that doses in the range of 200 to 600 mg chlorpromazine equivalents made akathisia roughly 1.4 times more likely than doses below 200 mg, and women were about four times more likely to develop it than men.3PLoS ONE. Psychotropic medications induced parkinsonism and akathisia in people attending follow-up treatment at Jimma Medical Center, Psychiatry Clinic Akathisia matters beyond comfort: it is sometimes mistaken for worsening agitation and treated with a higher dose of the very drug causing it, which makes things worse.
Tardive Dyskinesia
While parkinsonism and akathisia tend to appear within weeks of starting treatment and are often reversible, tardive dyskinesia is a different beast. It involves involuntary repetitive movements, most often of the face: lip smacking, tongue protrusion, chewing motions, grimacing. It can also affect the trunk and limbs. Tardive dyskinesia typically develops after months or years of continuous antipsychotic use, and in many cases it persists even after the medication is stopped.
Risk factors for tardive dyskinesia include older age, female sex, longer duration of illness, higher cumulative antipsychotic doses, and a history of early parkinsonian side effects or akathisia during treatment.4Journal of the Neurological Sciences. Risk factors and prevention of tardive dyskinesia Diabetes, smoking, and alcohol or substance use also increase the risk. Advancing age appears to be the single most significant factor.5PubMed Central. Assesment of Risk Factors for Tardive Dyskinesia The use of older antipsychotics like chlorpromazine (classified as first-generation agents) carries higher tardive dyskinesia risk than newer second-generation drugs.6Journal of the Neurological Sciences. Risk factors and prevention of tardive dyskinesia
One of the more frustrating aspects of tardive dyskinesia is that early parkinsonian side effects and akathisia actually predict its later development. In other words, the very movement problems that chlorpromazine causes in the short term serve as warning signs for a potentially irreversible movement disorder down the road. This makes monitoring during the first months of treatment especially important.
Neuroleptic Malignant Syndrome
The most feared side effect of chlorpromazine and other antipsychotics is neuroleptic malignant syndrome, a rare but potentially fatal reaction. It is characterized by high fever, severe muscle rigidity sometimes described as “lead pipe” stiffness, altered consciousness, and instability in heart rate and blood pressure.7PubMed Central. Neuroleptic malignant syndrome: a review for neurohospitalists Muscle breakdown can become severe enough to damage the kidneys, and complications include difficulty breathing and swallowing.8General Pharmacology: The Vascular System. Pathogenesis and treatment of neuroleptic malignant syndrome
Neuroleptic malignant syndrome can occur with virtually any antipsychotic, but it was first identified with older drugs like chlorpromazine and haloperidol. It is unpredictable in the sense that it does not follow a clear dose-response pattern, and it can strike at any point during treatment, not just at the start. The syndrome requires emergency treatment: stopping the antipsychotic, aggressive cooling, and sometimes medications to relax the muscles and restore dopamine signaling. Without prompt recognition, it can be fatal.
Weight Gain and Metabolic Problems
Chlorpromazine reliably causes weight gain. This is partly related to its strong antihistamine activity, which increases appetite, and partly to direct metabolic effects. Animal research has shown that chlorpromazine raises fasting glucose and insulin levels and interferes with the body’s ability to use adiponectin, a hormone that helps regulate blood sugar and fat metabolism.9PubMed. The elucidation of the mechanism of weight gain and glucose tolerance abnormalities induced by chlorpromazine The result is that chlorpromazine pushes the body toward insulin resistance, the precursor to type 2 diabetes. In people already at risk for metabolic syndrome, chlorpromazine can accelerate the process.
The metabolic effects are not just a cosmetic concern. Weight gain, elevated blood sugar, and abnormal lipid levels contribute to long-term cardiovascular risk, which is already elevated in people with serious mental illness for a variety of reasons. For someone on chlorpromazine long-term, regular monitoring of weight, blood sugar, and lipids is standard practice.
Prolactin Elevation and Its Consequences
Dopamine normally acts as a brake on prolactin secretion from the pituitary gland. When chlorpromazine blocks dopamine receptors in this pathway, prolactin levels rise, sometimes substantially. All older antipsychotics share this effect.10JAMA Psychiatry. Neuroleptic-induced Prolactin Level Elevation and Breast Cancer: An Emerging Clinical Issue Elevated prolactin can cause breast tenderness and milk production in both men and women, menstrual irregularities, sexual dysfunction, and over time may contribute to reduced bone density. Some newer antipsychotics, like quetiapine, do not produce a sustained rise in prolactin, which is one reason clinicians sometimes prefer them.11PubMed. A comparison of quetiapine and chlorpromazine in the treatment of schizophrenia
Eye and Skin Changes
Prolonged chlorpromazine use, particularly at higher doses over years, can cause deposits on the cornea and the front surface of the lens inside the eye. These deposits are thought to result from the drug accumulating in the fluid that bathes the eye’s internal structures, eventually aggregating with lens proteins.12Clinical Eye and Vision Care. Chlorpromazine: Case report and review of its ocular side-effects In some cases the opacities progress enough to impair vision.13PubMed. Kerato-lenticular ocular deposits and visual impairment with prolonged chlorpromazine use: A case series The changes are usually bilateral, affecting both eyes.
Skin changes often accompany the eye findings. Chlorpromazine can cause a distinctive blue-gray discoloration in sun-exposed areas of the skin. One reported case developed this pigmentation along with corneal and lens opacities after seven years of treatment.14PubMed. Chlorpromazine-induced skin pigmentation with corneal and lens opacities The pigmentation is related to the drug’s interaction with melanin and its metabolites depositing in the skin under ultraviolet light exposure. Chlorpromazine also causes photosensitivity, meaning sunburn occurs more easily. People taking the drug long-term are generally advised to use sunscreen and have regular eye exams.
Liver Injury
Chlorpromazine-related jaundice was recognized early in the drug’s history. By the late 1950s, more than 120 cases had already been reported in the medical literature.15JAMA Internal Medicine. Chlorpromazine Jaundice: Clinical Course, Hepatic-Function Tests, and Pathologic Findings—Summary of Twenty Cases The jaundice is typically cholestatic, meaning bile flow from the liver is obstructed rather than the liver cells themselves being destroyed. It usually appears within the first few weeks of treatment and is thought to be an allergic-type reaction rather than a straightforward dose-dependent toxic effect. Most cases resolve after the drug is stopped, but the reaction is important to catch early because it means the liver is under significant stress.
Blood Cell Abnormalities
Chlorpromazine can, rarely, cause agranulocytosis, a dangerous drop in white blood cells that leaves a person vulnerable to serious infections. This risk is often overlooked because clinicians associate agranulocytosis primarily with clozapine, which has mandatory blood monitoring programs. But chlorpromazine can cause it too, and because there is no routine monitoring requirement for chlorpromazine’s blood counts, cases sometimes go unrecognized until a patient develops a serious infection.16PubMed. Chlorpromazine-induced agranulocytosis: a case report A sudden unexplained fever or sore throat in someone taking chlorpromazine warrants a blood count check.
Seizure Risk
Chlorpromazine lowers the seizure threshold, meaning it makes seizures more likely in people who are already vulnerable, such as those with epilepsy or a history of head injury. Among antipsychotics, chlorpromazine is considered one of the more likely to provoke seizures, particularly at higher doses.17PubMed. Antipsychotics and seizures: higher risk with atypicals? This is relevant in overdose situations as well, where seizures are one of the possible complications.
Pregnancy and Breastfeeding
Chlorpromazine crosses the placenta, and babies exposed to it before birth can show movement abnormalities resembling the extrapyramidal side effects seen in adults. These effects may persist for weeks after delivery.18Australian Prescriber. Antipsychotic drugs in pregnancy and breastfeeding Other suspected withdrawal symptoms in newborns exposed in the womb include paralytic ileus (where the gut stops moving), fever, episodes of turning blue, and transient heart rhythm abnormalities.19Australian Prescriber. Antipsychotic drugs in pregnancy and breastfeeding Respiratory distress has also been reported.20PubMed Central. The potential risks of commonly prescribed antipsychotics: during pregnancy and lactation
These risks do not necessarily mean chlorpromazine can never be used during pregnancy. Untreated psychosis carries its own serious dangers for both the mother and the baby. But the decision requires careful weighing of risks, and if an antipsychotic is needed during pregnancy, clinicians often prefer agents with more safety data in that context.
The Emotional Toll of Treatment
Beyond the physical side effects, chlorpromazine and similar older antipsychotics can produce a subjective state called neuroleptic dysphoria, a persistent flattening of mood and motivation that goes beyond simple sedation. People describe feeling emotionally blunted, disconnected, or unable to experience pleasure. This is not a minor complaint. Persistent dysphoria is a major driver of treatment non-adherence, and it has been linked to substance abuse, poorer clinical outcomes, increased suicidality, and reduced quality of life.21PubMed. Neuroleptic dysphoria: towards a new synthesis
This side effect is one reason why the shift toward newer antipsychotics happened even before the movement disorder risks were well quantified. When patients consistently report that a medication makes them feel less like themselves, adherence drops, and an antipsychotic that a person won’t take is an antipsychotic that doesn’t work.
How Chlorpromazine Compares to Newer Antipsychotics
A Cochrane systematic review comparing chlorpromazine to second-generation (atypical) antipsychotics found that people receiving chlorpromazine experienced significantly more extrapyramidal symptoms. Across multiple trials, the risk of movement side effects was roughly eight times higher with chlorpromazine than with the newer drugs it was compared against.22PubMed Central. Chlorpromazine versus atypical antipsychotic drugs for schizophrenia The quality of the underlying evidence was rated as low, which is common in older psychiatric drug trials, but the magnitude of the difference was large enough that the direction of the finding is not in serious doubt.
Newer antipsychotics are not free of side effects. Many cause even more weight gain than chlorpromazine, and some carry their own movement disorder risks, just lower ones. But the gap in extrapyramidal symptoms is real and substantial, and it is a major reason chlorpromazine has been displaced as a first-line treatment in most high-income countries. In settings where drug availability and cost are significant constraints, chlorpromazine remains widely used because it is inexpensive and reliably effective against acute psychosis.
What Happens in Overdose
Chlorpromazine overdose produces deep sedation, and a substantial fraction of cases become severe. In a case series of chlorpromazine overdose presentations, about a quarter of patients had a very depressed level of consciousness, roughly a quarter required intensive care admission, and about 15 percent needed a breathing tube. Delirium occurred in about 8 percent, low blood pressure in about 4 percent, and seizures were uncommon but did occur. One death was recorded in the series.23Taylor & Francis Online (Clinical Toxicology). Chlorpromazine overdose: a case series The cardiovascular effects of overdose, including abnormal heart rhythms and QT prolongation, are among the most dangerous features. Treatment is primarily supportive: securing the airway, managing low blood pressure with fluids, and monitoring the heart rhythm closely.
The sedation from chlorpromazine overdose can develop rapidly, which means a person who has taken too much may lose the ability to protect their own airway before arriving at a hospital. Anyone who suspects a chlorpromazine overdose should seek emergency care immediately rather than waiting to see how the person feels.
Sedation, Dry Mouth, Constipation, and Other Everyday Complaints
The side effects that receive the most clinical attention are the dangerous ones, but the day-to-day side effects of chlorpromazine are what patients most often complain about. Sedation is often the most prominent, especially early in treatment. Chlorpromazine blocks histamine receptors aggressively, which produces drowsiness that can be incapacitating at higher doses. Many people adjust to the sedation over days to weeks, but some do not.
Anticholinergic effects round out the everyday burden. Dry mouth, constipation, urinary retention, and blurred vision are common. Orthostatic hypotension, a sudden drop in blood pressure upon standing that causes dizziness or fainting, is also frequent, particularly in older adults. These effects are rarely dangerous on their own, but they add up. A person who is sedated, constipated, dizzy when standing, and unable to enjoy much of anything emotionally has a strong incentive to stop taking the medication, which brings us back to the adherence problem that runs through every discussion of antipsychotic side effects.
For all these reasons, chlorpromazine’s place in modern psychiatry is a complicated one. It remains on the World Health Organization’s List of Essential Medicines because it works, it is cheap, and it is available almost everywhere. But its side-effect profile means that where alternatives are accessible, clinicians tend to reach for them first, reserving chlorpromazine for situations where cost, availability, or a specific clinical need tips the balance back in its favor.