Unintended lactation, medically termed galactorrhea, is a milky nipple discharge not associated with pregnancy or breastfeeding. While other causes exist, drug-induced hyperprolactinemia, or elevated prolactin levels due to medication, is a frequent culprit. This occurs when drugs interfere with the body's prolactin regulation, primarily by disrupting the dopamine pathway. Dopamine from the hypothalamus normally inhibits prolactin release from the pituitary gland. Medications that block dopamine receptors can lift this inhibition, leading to increased prolactin and galactorrhea. This can manifest in both women, potentially affecting menstrual cycles and fertility, and men, possibly causing erectile dysfunction and gynecomastia (breast enlargement).
Key Medications Known to Induce Galactorrhea
Various drug classes are associated with hyperprolactinemia, with some posing a higher risk.
Antipsychotic Medications
Both first- and second-generation antipsychotics are used for conditions like schizophrenia and bipolar disorder and are known to block dopamine D2 receptors. Among second-generation drugs, risperidone and paliperidone are particularly associated with significantly elevated prolactin levels.
Antidepressants
Some antidepressants can cause mild prolactin increases. Rarely selective serotonin reuptake inhibitors (SSRIs) such as sertraline and fluoxetine have been linked to elevated prolactin and galactorrhea.
Gastrointestinal and Anti-nausea Drugs
These medications often block dopamine receptors to improve gut motility and reduce vomiting. Metoclopramide (Reglan) is a well-known cause of galactorrhea and carries a warning regarding potential hyperprolactinemia with long-term use. Domperidone is another dopamine antagonist used for similar purposes.
Antihypertensives
Certain blood pressure medications can interfere with dopamine. Methyldopa is known to increase prolactin by affecting the central nervous system. Verapamil, a calcium-channel blocker, has also been associated with hyperprolactinemia.
Opioids
Opioids like morphine and heroin can decrease hypothalamic dopamine and raise prolactin.
How Different Drug Classes Affect Prolactin
| Drug Class | Examples | Mechanism of Action | Typical Prolactin Level Increase |
|---|---|---|---|
| Antipsychotics | Risperidone, Haloperidol | Blocks dopamine D2 receptors, inhibiting prolactin suppression. | High; can exceed 100 ng/mL. |
| Anti-Nausea Drugs | Metoclopramide, Domperidone | Blocks dopamine D2 receptors in the pituitary. | High; metoclopramide can cause levels >100 ng/mL. |
| Antidepressants | SSRIs (Sertraline), TCAs (Amitriptyline) | Less understood; can involve serotonin-mediated inhibition of dopamine neurons. | Mild; often within or slightly above normal range. |
| Antihypertensives | Methyldopa, Verapamil | Decreases central dopamine or inhibits its release. | Variable; typically mild to moderate. |
Recognizing and Managing Drug-Induced Galactorrhea
Milky nipple discharge warrants consultation with a healthcare provider to rule out other conditions like a prolactinoma. Diagnosis typically involves reviewing medical history and medications, a physical examination, measuring prolactin levels via blood tests, and potentially an MRI of the pituitary gland.
Management usually involves identifying and stopping the problematic medication under medical supervision. Doctors may switch the patient to a 'prolactin-sparing' alternative; for instance, aripiprazole is an antipsychotic with dopamine agonist properties that can lower prolactin. In some cases, aripiprazole might be added to an existing antipsychotic regimen to manage the side effect. Galactorrhea is generally reversible, with symptoms resolving weeks to months after stopping the offending drug.
Conclusion
Unintended lactation due to medication is a manageable side effect. A correct diagnosis by a healthcare professional is crucial to identify the causative drug and adjust treatment. Management often involves discontinuing or switching the medication to address the underlying hyperprolactinemia. Open communication with a doctor is essential for a safe and effective treatment plan. For further information, the Endocrine Society offers comprehensive resources on hyperprolactinemia.
