What medications cause lactation as a side effect?

October 10, 2025 •

4 min read

According to the National Center for Biotechnology Information (NCBI), drug-induced hyperprolactinemia, or abnormally high prolactin levels, is the most common cause of consistently elevated prolactin levels. The unexpected milk production, or galactorrhea, is a potential side effect of certain medications that interfere with the body's hormonal regulation.

Quick Summary

Several medications can trigger galactorrhea by increasing prolactin levels, primarily by blocking dopamine receptors. These include antipsychotics, gastrointestinal drugs, certain antidepressants, and some antihypertensives. Management typically involves dose adjustment or medication changes under medical supervision. The underlying mechanism involves a disruption of hormonal balance.

Key Points

Dopamine Inhibition: The majority of medications causing galactorrhea do so by blocking dopamine's natural inhibitory effect on prolactin secretion from the pituitary gland.
Antipsychotics are Major Culprits: First-generation antipsychotics and some second-generation ones, like risperidone and paliperidone, have a high potential for causing elevated prolactin levels.
GI Medications can also be a Cause: Drugs used for nausea and gastric motility, such as metoclopramide and domperidone, can cause this side effect by blocking dopamine receptors.
Medical Consultation is Crucial: If you experience lactation unexpectedly, it is important to consult a healthcare provider to confirm the cause and rule out other conditions like pituitary tumors.
Treatment Often Involves Medication Changes: Managing drug-induced galactorrhea usually involves adjusting the dose, switching to an alternative drug, or prescribing a dopamine agonist to lower prolactin.
Men Can Experience This Too: Both men and women can experience drug-induced galactorrhea, with men sometimes also experiencing gynecomastia (breast enlargement).

The Link Between Medications and Hyperprolactinemia

Lactation, or milk production, is regulated by the hormone prolactin, which is secreted by the pituitary gland. In a non-pregnant, non-lactating state, the secretion of prolactin is continuously inhibited by dopamine, a neurotransmitter produced in the hypothalamus. When a medication blocks the action of dopamine, this inhibitory effect is lifted, causing prolactin levels to rise. This condition is known as hyperprolactinemia and is the primary driver of drug-induced galactorrhea.

Classes of Medications that Cause Lactation

Several classes of drugs are known to cause hyperprolactinemia and subsequent galactorrhea. These include:

Antipsychotic medications: Both typical (first-generation) and certain atypical (second-generation) antipsychotics are frequent causes of hyperprolactinemia. They primarily act by blocking dopamine D2 receptors. Risperidone and its active metabolite, paliperidone, are notorious for causing a significant and sustained increase in prolactin levels. Other examples include haloperidol, phenothiazines (e.g., chlorpromazine), and amisulpride.
Gastrointestinal (GI) agents: Drugs used to treat nausea, vomiting, and acid reflux often work by blocking dopamine receptors in the GI tract, but this effect can also increase prolactin systemically. Metoclopramide and domperidone are well-known examples. Metoclopramide, in particular, can cause significant prolactin elevation and has been used off-label as a galactagogue (a substance that promotes lactation).
Antidepressants: While the risk is generally lower than with antipsychotics, certain antidepressants can also cause hyperprolactinemia. Selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) have been implicated. The mechanism is believed to involve the indirect effect of serotonin on the dopaminergic system.
Antihypertensive medications: Some blood pressure medications have been shown to increase prolactin. Methyldopa, for instance, is a competitive inhibitor of dopamine synthesis, leading to less dopamine and more prolactin. Other examples include reserpine and the calcium channel blocker verapamil.
Opioids: Chronic opioid use has been linked to hyperprolactinemia and potential galactorrhea. The mechanism is complex but involves the suppression of hypothalamic-pituitary axes, leading to hormonal imbalances.
H2 receptor antagonists: Certain medications for stomach acid reduction, like cimetidine, can block H2 receptors, which may indirectly stimulate prolactin secretion.
Hormonal therapies: Estrogen-containing birth control pills or hormone replacement therapy can sometimes cause galactorrhea due to their effects on prolactin release.

A Deeper Look into the Mechanism

The tuberoinfundibular dopamine pathway is a crucial neuroendocrine system that connects the hypothalamus to the pituitary gland. Dopamine released in this pathway acts directly on D2 receptors on prolactin-producing cells in the pituitary, effectively preventing prolactin release. Drugs that block these D2 receptors disrupt this normal inhibitory function, leading to unchecked prolactin production and secretion into the bloodstream. The extent of the prolactin increase and the subsequent risk of galactorrhea can depend on the drug's potency and its ability to cross the blood-brain barrier.

Management and Treatment Strategies

If a patient experiences galactorrhea as a side effect, a healthcare provider should be consulted to confirm the cause and determine the best course of action. This is crucial because galactorrhea can also be caused by other underlying conditions, such as a benign pituitary tumor (prolactinoma).

Medication Adjustment: The most straightforward approach is to adjust the dose or switch to an alternative medication that does not cause hyperprolactinemia. For example, in the case of antipsychotics, switching to a prolactin-sparing agent like aripiprazole may be an option.
Dopamine Agonists: In some cases, a doctor might prescribe a dopamine agonist like cabergoline or bromocriptine. These drugs mimic dopamine and help suppress prolactin production. Cabergoline is often preferred due to its higher efficacy and tolerability.
Hormone Replacement: If hyperprolactinemia has led to low estrogen levels and associated symptoms, hormone replacement therapy might be considered.
Addressing Underlying Conditions: For cases where galactorrhea persists or is not medication-related, further investigation is necessary to rule out or treat other underlying medical conditions.

Comparison of Drug Classes and Their Prolactin-Elevating Potential


Drug Class	Mechanism of Action	Common Examples	Prolactin-Elevating Potential	Associated Symptoms
Antipsychotics (Typical)	Strong dopamine D2 receptor blockade	Haloperidol, Chlorpromazine	High	Galactorrhea, amenorrhea, sexual dysfunction
Antipsychotics (Atypical)	Mixed D2 and serotonin receptor blockade	Risperidone, Paliperidone	High (Risperidone) to Low (Quetiapine)	Galactorrhea, menstrual changes
GI Motility Agents	Dopamine D2 receptor blockade	Metoclopramide, Domperidone	High	Galactorrhea, gynecomastia
Antidepressants	Indirectly affecting dopamine via serotonin/norepinephrine	SSRIs, TCAs	Low to Moderate	Galactorrhea (less common, often case reports)
Antihypertensives	Inhibits dopamine synthesis or release	Methyldopa, Reserpine	Moderate to High	Galactorrhea
Opioids	Complex effects on hypothalamic-pituitary axis	Morphine, Methadone	Variable (chronic use higher)	Hyperprolactinemia

Conclusion

Galactorrhea can be a surprising and distressing side effect of many medications, though it is often a benign condition caused by drug-induced hyperprolactinemia. The key mechanism involves the disruption of the normal dopamine-prolactin balance. Common culprits include antipsychotics, certain gastrointestinal drugs, and some antidepressants and antihypertensives. For patients experiencing this, discussing the issue with a healthcare provider is essential. It's often possible to manage the condition by adjusting the medication or switching to an alternative. For more information on hyperprolactinemia, you can consult resources like the Mayo Clinic website.

Frequently Asked Questions

Drug-induced galactorrhea is the abnormal production of milk, not related to childbirth or breastfeeding, that occurs as a side effect of certain medications. It is typically caused by elevated levels of the hormone prolactin, a condition known as hyperprolactinemia.

Antipsychotics, particularly older generations and specific atypical types like risperidone, are most commonly associated with this side effect due to their potent dopamine-blocking effects. Gastrointestinal motility agents like metoclopramide are also high-risk culprits.

Yes, some antidepressants, including SSRIs and TCAs, have been reported to cause galactorrhea, although less frequently than antipsychotics. The mechanism is believed to be related to the effect of serotonin on the dopamine system that regulates prolactin.

The main mechanism is the blockage of dopamine D2 receptors. Dopamine normally inhibits prolactin production, so blocking its receptors removes this inhibitory control, leading to increased prolactin secretion.

Besides galactorrhea, other symptoms can include menstrual irregularities (oligomenorrhea or amenorrhea), sexual dysfunction, and, in the long term, potential bone loss due to hypoestrogenism.

You should not stop taking your medication abruptly. Instead, speak with your healthcare provider immediately. They can evaluate your symptoms, confirm the cause, and discuss adjusting the dosage or switching to an alternative medication if necessary.

Yes, men can experience galactorrhea as a side effect of medication. For instance, risperidone has been reported to cause lactation and gynecomastia (breast enlargement) in adolescent and adult males.