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Butyrophenones

For medical students2 min readUpdated 2026-10-10

Butyrophenones are a class of high-potency antipsychotics with profound neuroleptic activity. They effectively manage psychomotor agitation and surpass many classical agents in potency, though their clinical use requires careful monitoring due to a high risk of movement disorders.

PotencyAntipsychotic activity is 50–100 times higher than that of phenothiazines.

AbsorptionThe drugs demonstrate good absorption when administered orally through the gastrointestinal tract.

Side EffectsCharacterized by the development of prominent extrapyramidal symptoms.

HemodynamicsPractically do not lower blood pressure due to weak peripheral alpha-adrenoreceptor blockade.

Pharmacological Profile

Butyrophenones are distinguished by their marked antipsychotic activity. In terms of specific potency, they exceed classical phenothiazine derivatives by 50 to 100 times.

In addition to their primary neuroleptic effect, these agents possess important adjunctive properties:

Sedative effect — promotes calming of the nervous system.
Antiemetic effect — suppresses the vomiting reflex.

An important difference between butyrophenones and phenothiazines is their receptor profile. This group completely lacks anticholinergic (antimuscarinic) properties. Furthermore, they exert only a weak blockade of peripheral $\alpha$-adrenoreceptors. As a result, the drugs have virtually no impact on vascular tone and do not cause significant hypotension.

Drug Interactions

Butyrophenones interact actively with other agents affecting the central nervous system. Following rapid absorption from the gastrointestinal tract, they can significantly alter the effects of concurrent therapy.

Potentiation (Synergism): Drugs in this group significantly enhance the effects of other CNS depressants, including:

General anesthetics;
Sedatives and hypnotics;
Opioid analgesics;
Alcohol.

Antagonism: With respect to psychostimulants, butyrophenones act as antagonists, suppressing their stimulating effects on the psyche.

Key Agents of the Group

In clinical practice, two primary representatives are most frequently utilized, differing in duration of action and indications.

Haloperidol

A high-potency antipsychotic with a pronounced sedative component. Indications:

Management of acute psychomotor agitation.
Treatment of patients whose condition is resistant to other neuroleptics.
Conditions where chlorpromazine is indicated (similar therapeutic spectrum).

Haloperidol frequently causes motor side effects and is therefore strictly contraindicated in any CNS disorders already accompanied by extrapyramidal symptoms.

Droperidol

Characterized by a very strong, yet short-acting antipsychotic effect. Indications:

Emergency management of acute psychomotor agitation (administered as a 0.25% solution).
Neuroleptanalgesia — a specialized form of anesthesia combining droperidol with a potent opioid analgesic, fentanyl (available in a fixed-dose combination preparation).

Adverse Reactions

The primary and most hazardous adverse effect across the entire class of butyrophenones is the high incidence of extrapyramidal symptoms (EPS). This constellation of severe movement disorders requires vigilant patient monitoring during therapy and limits their use in individuals with pre-existing lesions of the relevant basal ganglia structures.

Frequently asked questions

What is the mechanism of the antipsychotic action of butyrophenones?

The antipsychotic mechanism involves the blockade of postsynaptic dopamine (D₂) receptors in the central nervous system. Additionally, most neuroleptics block presynaptic dopamine (D₃), serotonin (5-HT), norepinephrine (α₁), histamine (H₁), and muscarinic acetylcholine (M) receptors. However, the receptor profile of butyrophenones differs: they completely lack anticholinergic properties and show only weak peripheral α-adrenoreceptor blockade, which explains why they rarely lower blood pressure.

What are the contraindications for haloperidol?

The primary contraindication for haloperidol is central nervous system disease accompanied by extrapyramidal symptoms, as haloperidol frequently induces extrapyramidal disorders. Neuroleptics are also contraindicated for treating anticholinergic-induced psychosis.

What specific extrapyramidal disorders do butyrophenones cause?

Butyrophenones cause early (reversible) and late (irreversible) extrapyramidal disorders. These movement abnormalities include:

Drug-induced parkinsonism — manifesting as resting tremor, muscle rigidity, and hypokinesia (motor retardation).
Acute dystonia — spastic muscle contractions localized in the face, neck, and back.
Akathisia — marked motor restlessness and an inability to sit still.
Tardive dyskinesia — persistent involuntary hyperkinetic movements of the facial muscles (chewing, lip-smacking, blinking) and neck.

Why do butyrophenones rarely cause hypotension?

Unlike phenothiazines, they completely lack anticholinergic properties and only minimally block peripheral alpha-adrenoreceptors, thus avoiding significant drops in blood pressure.

Which drug combinations are dangerous with this class?

Alcohol, general anesthetics, hypnotics, and opioid analgesics, because butyrophenones sharply potentiate their central nervous system depression.

What is neuroleptanalgesia and which agent is used for it?

It is a method of combined anesthesia and sedation. It utilizes the short-acting antipsychotic droperidol coupled with the opioid analgesic fentanyl.

What is the primary contraindication for haloperidol?

Haloperidol is contraindicated in central nervous system disorders accompanied by extrapyramidal symptoms, as it frequently precipitates severe movement disorders.

Go deeper

Mechanism of extrapyramidal symptoms induced by neuroleptics
Comparison of chlorpromazine and haloperidol: safety profile
Principles and stages of neuroleptanalgesia
Management strategies for patients resistant to standard neuroleptics