Chlorpromazine side effects: anticholinergic, photosensitivity, hypotension

Chlorpromazine, marketed historically as Thorazine, was the first effective antipsychotic medication. Its 1954 approval is widely considered the start of modern psychopharmacology — the first time a medication could reliably reduce the positive symptoms of psychosis and allow patients to be discharged from long-term hospitalisation. Seventy years later, it is largely replaced for first-line use by atypicals, but it is still on the WHO Model List of Essential Medicines and is still prescribed in some clinical situations and many parts of the world. Its side-effect profile is one of the most thoroughly characterised in psychiatry.

Why the side effect profile is so broad

Unlike haloperidol, which targets dopamine D2 receptors fairly selectively, chlorpromazine binds many receptor classes:

• Histamine H1 — strong; produces heavy sedation and weight gain
• Muscarinic acetylcholine — strong; produces dry mouth, constipation, blurred vision, urinary retention
• Alpha-1 adrenergic — strong; produces orthostatic hypotension
• Dopamine D2 — moderate; produces antipsychotic effect and EPS, though less EPS per unit dose than haloperidol
• Serotonin 5-HT2A — modest

This broad binding pattern is why low-potency typicals like chlorpromazine and thioridazine are sedating but cause less acute EPS than high-potency typicals like haloperidol or fluphenazine — and why they cause more anticholinergic, cardiovascular, and metabolic side effects in exchange.

Anticholinergic effects

The anticholinergic side effect cluster is among the most clinically prominent on chlorpromazine:

• Dry mouth — almost universal; can affect dental health long-term. See our dry mouth guide.
• Constipation — common; can become severe. See our constipation guide.
• Blurred vision — particularly close-up; usually settles
• Urinary retention — particularly in older men with prostate enlargement
• Cognitive slowing or confusion — particularly in older adults

The cognitive impact in older adults is one of several reasons chlorpromazine and other strongly anticholinergic antipsychotics are generally avoided in elderly patients with dementia.

Sedation

Chlorpromazine is one of the most sedating antipsychotics — comparable to or greater than quetiapine or olanzapine. This is partly why it has historically been used in acute agitation and is sometimes called "chemical restraint" in older texts. For maintenance treatment, the sedation often improves over weeks but can persist.

Orthostatic hypotension

Chlorpromazine's strong alpha-1 blockade produces significant orthostatic hypotension, particularly during titration and in older patients. Falls are a real risk. Mitigation:

• Slow titration
• Standing up slowly
• Adequate hydration
• Avoidance of alcohol
• Caution with concurrent antihypertensives

Photosensitivity: the distinctive one

Chlorpromazine causes photosensitivity reactions in a substantial fraction of patients — sometimes severe sunburn after relatively brief sun exposure. The drug accumulates in skin and eyes and is photoactive. With long-term use, blue-grey skin pigmentation can develop in sun-exposed areas, sometimes only partially reversible after discontinuation.

Practical strategies:

• Daily broad-spectrum sunscreen (SPF 30+) on exposed skin
• Long sleeves, hats, and physical sun protection
• Avoidance of midday sun where possible
• Annual eye examinations — chlorpromazine can also cause corneal and lens deposits over time

Movement effects

Acute EPS rates with chlorpromazine are lower than with haloperidol because of its anticholinergic activity (anticholinergics are themselves used to treat EPS, so the drug is, in a sense, partly self-treating). But long-term tardive dyskinesia risk is similar to other typicals. Periodic AIMS screening is standard.

Metabolic effects

Chlorpromazine produces moderate weight gain — comparable to risperidone or paliperidone, less than olanzapine or clozapine. Effects on glucose and lipids are present and warrant standard monitoring.

Liver effects

Chlorpromazine has been associated with cholestatic hepatitis — a reversible liver inflammation that can present with jaundice, pruritus, and fatigue. It is uncommon but is one of the reasons baseline and periodic liver function tests are reasonable. Most cases resolve when the drug is stopped.

Cardiac effects

QT prolongation occurs with chlorpromazine, more than with most atypicals, less than with thioridazine. Caution in patients with cardiac disease or on other QT-prolonging medications. See QT prolongation.

Prolactin

Chlorpromazine elevates prolactin substantially, similar to other dopamine-blocking antipsychotics. See hyperprolactinemia.

Rare but serious

• Neuroleptic malignant syndrome — rare, life-threatening
• Cholestatic hepatitis — uncommon, usually reversible
• Agranulocytosis — rare, but reported; warrants attention to fever or signs of infection
• Pigmentary retinopathy — uncommon at therapeutic doses; more common with the related drug thioridazine

Approved uses today

Chlorpromazine remains FDA-labelled for several indications:

• Schizophrenia
• Acute mania of bipolar disorder
• Severe behavioural problems in children with combativeness or severe hyperexcitability
• Intractable hiccups
• Nausea and vomiting (historically; less commonly used for this now)
• Pre-anaesthetic and acute intermittent porphyria use

Boxed warning

• Increased mortality in elderly patients with dementia-related psychosis (class-wide)

When to call the prescriber

• Severe dry mouth, constipation, or urinary retention
• Persistent dizziness or fainting
• Significant sunburn or skin colour changes
• Vision changes
• Yellowing of the skin or eyes (possible cholestatic hepatitis)
• Fever or signs of infection (uncommon but possible blood effects)
• Restlessness, tremor, stiffness, or involuntary movements

Switching considerations

For patients on chlorpromazine who want a more modern alternative, common moves include:

• Olanzapine — also broad-spectrum and sedating, but with less anticholinergic and photosensitivity burden (though heavier metabolic effects)
• Quetiapine — sedating, fewer anticholinergic effects, less prolactin
• Risperidone — less sedating, more EPS/prolactin
• Aripiprazole — much less sedating, less anticholinergic, more activating

Why chlorpromazine endures

Despite its age and side-effect burden, chlorpromazine remains globally important. It is on the WHO Model List of Essential Medicines, available widely as a cheap generic, and effective for symptoms that have not responded to other agents. In high-income countries it is rarely first-line in 2026, but it is not obsolete — it is one of the foundational tools of psychiatric medicine, with seven decades of accumulated knowledge about how to use it safely.

This article is for educational purposes only and is not medical advice. Information is summarised from publicly available FDA labelling and peer-reviewed literature. Always consult your prescribing clinician before starting, stopping, or changing any medication. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.