Extrapyramidal side effects
Benperidol can cause extrapyramidal side effects due to its dopamine receptor blocking effects. These include:
- Dystonia – sustained muscle spasms and abnormal movements, especially of face, neck and back. Can appear shortly after starting or changing dosage.
- Akathisia – uncomfortable sensations of inner restlessness that causes an inability to sit still. Feeling of irritability and urge to move.
- Parkinsonism – tremors, rigid muscles, impaired speech, mask-like face. Can occur at high doses or long term treatment.
- Tardive dyskinesia – slow, repetitive, uncontrollable movements, especially of tongue, face and mouth. Usually appears after long term use or high dosages. May be irreversible. Sedation and drowsiness
Benperidol activates histamine H1 receptors which can cause sedation, drowsiness and impaired alertness. This risk is higher at the start of treatment or when doses are increased. Patients should be advised against driving or operating heavy machinery.
Orthostatic hypotension
Due to its alpha-adrenergic blocking effects, benperidol may cause a drop in blood pressure upon standing from sitting or lying down. Can lead to dizziness, lightheadedness and falls. Patient should change positions slowly. Blood pressure monitoring may be required.
Anticholinergic effects
By blocking muscarinic receptors, benperidol produces anticholinergic effects like:
- Dry mouth, blurred vision, constipation – due to reduced parasympathetic stimulation.
- Urinary retention – especially in men with prostatic hyperplasia. Close monitoring required.
- Memory impairment and confusion – higher risk in elderly patients. Lower doses and close monitoring advised.
QT prolongation
Benperidol can prolong the QT interval on ECG, increasing risk of ventricular arrhythmias. Patients with cardiac conditions may be at higher risk. Close monitoring required and ECG may be needed, especially with IV administration or overdose.
Other effects
Additional adverse effects include hypertension or hypotension, tachycardia, weight gain, and hyperprolactinemia which can cause menstrual changes, breast engorgement, and gynecomastia.
In summary, benperidol can produce a number of troublesome side effects due its wide range of pharmacological actions. Careful dosing, titration, and monitoring are necessary to limit side effects. In many cases, lower doses or switching to alternative antipsychotics may be required if side effects are severe or persistent.