Read this topic

Prolactin is a hormone released by the pituitary gland that, outside pregnancy and breastfeeding, is normally kept LOW by dopamine's inhibitory effect on the pituitary. Antipsychotics work by blocking dopamine receptors, and blocking dopamine in the pituitary removes that inhibition, so prolactin rises. Hyperprolactinaemia (an abnormally raised blood prolactin level) is therefore one of the most predictable, mechanism-explained side effects in the whole of psychopharmacology, and knowing WHICH drugs raise it, WHICH lower it, and how to manage it is a recurring exam theme.

Hyperprolactinaemia management is the structured approach to a raised prolactin level found in a patient on antipsychotic treatment: confirming the cause is the medication rather than another pathology, assessing whether it is causing symptoms, and adjusting treatment accordingly. It sits at the intersection of psychiatry and endocrinology (the medical specialty of hormones), because untreated hyperprolactinaemia has real long-term physical consequences, not just an abnormal blood test.

A common mistake is assuming every antipsychotic raises prolactin equally, or that a raised prolactin level is always due to the drug. Neither is true. Antipsychotics vary hugely in their prolactin effect depending on how strongly and how persistently they block the D2 dopamine receptor and how well they cross the blood-brain barrier, and any newly raised prolactin should still prompt basic screening for another cause, for example a prolactin-secreting pituitary tumour (a prolactinoma), before it is simply attributed to medication.

Imagine dopamine as a brake pedal that the pituitary gland normally keeps pressed down, holding prolactin release low. An antipsychotic that blocks dopamine receptors in the pituitary is like lifting that brake pedal: with the brake released, prolactin is free to rise. The strength of this effect tracks how tightly, and for how long, a drug binds the D2 receptor in that specific part of the brain, which is why different antipsychotics raise prolactin by very different amounts even though they share the same broad drug class.

Risperidone and amisulpride are the two antipsychotics most strongly associated with clinically significant hyperprolactinaemia, because both bind the D2 receptor tightly and, in risperidone's case, cross the blood-brain barrier poorly, concentrating their effect on the pituitary. The older first-generation antipsychotics (for example haloperidol and chlorpromazine) also reliably raise prolactin, as a class effect of strong dopamine blockade. Most other second-generation antipsychotics (olanzapine, quetiapine, clozapine) cause smaller or negligible prolactin rises in most patients, though individual variation exists. Aripiprazole is the deliberate exception: it is a partial dopamine agonist (a drug that activates the D2 receptor partially rather than blocking it fully), and this different mechanism means it typically LOWERS prolactin rather than raising it: switching a patient with symptomatic risperidone-induced hyperprolactinaemia to aripiprazole, or adding a small dose of aripiprazole alongside the existing antipsychotic, is a recognised strategy specifically because of this prolactin-lowering property.

Hyperprolactinaemia is not the same as neuroleptic malignant syndrome or other acute antipsychotic emergencies: it is a gradual, hormonal, usually non-emergency side effect rather than an acute medical crisis, and it does not require stopping the antipsychotic abruptly. It is also distinct from simple weight gain or metabolic syndrome, another antipsychotic side effect family with a different mechanism (histamine and serotonin receptor effects rather than dopamine blockade in the pituitary). And a raised prolactin found on a blood test is not automatically drug-induced hyperprolactinaemia: pregnancy, hypothyroidism (an underactive thyroid gland, which can itself raise prolactin), and a prolactinoma all need to be considered as look-alike causes of the same abnormal number.

Diagnosis starts with a blood prolactin level, ideally taken without recent stress or breast examination, both of which can transiently raise the result, and interpreted alongside the timing of antipsychotic dosing. Once a raised level is confirmed, basic screening for alternative causes (pregnancy testing, thyroid function tests for hypothyroidism, and a review of other prolactin-raising medications) helps establish that the antipsychotic really is the cause. Symptom assessment matters as much as the number: galactorrhoea (inappropriate milk production, in either sex), amenorrhoea or irregular periods, reduced libido, and erectile dysfunction all point toward a level that is clinically significant, not just statistically raised. A markedly elevated level, well above what medication alone typically causes, or one that fails to improve with the management steps below, should prompt pituitary imaging (an MRI) to exclude a prolactinoma before assuming the drug is fully responsible.

Once hyperprolactinaemia is confirmed as medication-induced and the patient is symptomatic, management follows a stepwise approach set out in the Maudsley Prescribing Guidelines: first, consider REDUCING the dose of the causative antipsychotic if clinically appropriate; if that is not enough or not appropriate, consider SWITCHING to a prolactin-sparing agent such as aripiprazole; adding aripiprazole to an existing antipsychotic is an alternative when switching is not desirable. Left untreated over the long term, chronic hyperprolactinaemia lowers oestrogen or testosterone enough to reduce bone mineral density, raising osteoporosis risk, which is why a persistently raised level is followed up rather than dismissed as a cosmetic or fertility-only issue.

Questions often present a patient on risperidone with amenorrhoea and galactorrhoea and expect recognition of drug-induced hyperprolactinaemia, with aripiprazole augmentation or switching as the correct next step, rather than simply stopping all antipsychotic treatment. A favourite trap lists aripiprazole among the "high-risk" drugs to test whether candidates remember it is the prolactin-LOWERING exception, not a prolactin-raising drug like risperidone or amisulpride.

Antipsychotics raise prolactin by blocking dopamine's normal inhibitory effect on the pituitary, with risperidone, amisulpride, and first-generation antipsychotics causing the largest rises and aripiprazole, a partial dopamine agonist, uniquely lowering it; diagnosis combines a blood level, symptom assessment, and excluding other causes such as a prolactinoma, and symptomatic cases are managed per Maudsley Prescribing Guidelines by dose reduction, switching, or aripiprazole augmentation.