Nipple discharge, the release of fluid from the breast, can be unexpected. While often associated with pregnancy or breastfeeding, it can occur for various reasons. In many instances, this symptom is benign, particularly as a side effect of certain medications.
Mechanisms of Medication-Induced Discharge
Medications can cause nipple discharge by disrupting hormonal balance, primarily by increasing prolactin levels. Prolactin, a hormone from the pituitary gland, stimulates milk production. Dopamine normally inhibits prolactin secretion.
When drugs interfere with dopamine’s effect or directly stimulate prolactin release, blood prolactin levels can rise, a condition known as hyperprolactinemia. This elevated prolactin can trigger nipple discharge. Some medications may also influence other hormonal pathways or directly affect breast tissue, but the dopamine-prolactin axis is a common pathway for drug-induced cases.
Key Medication Classes Associated with Discharge
Many medications can cause nipple discharge. Antipsychotics, especially older drugs like haloperidol and chlorpromazine, are known for this side effect due to their dopamine receptor blocking properties. Atypical antipsychotics, such as risperidone and paliperidone, also commonly elevate prolactin.
Antidepressants, including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants, can induce nipple discharge. These medications impact serotonin neurotransmission, which affects prolactin regulation. Certain blood pressure medications, such as methyldopa, reserpine, and verapamil, have been linked to discharge.
Opioids, including codeine, heroin, methadone, and morphine, can cause hyperprolactinemia by inhibiting dopaminergic neurons. While opioids may cause a transient increase in prolactin, their contribution to persistent discharge varies. Stomach medications, particularly metoclopramide, are common causes because they are strong dopamine receptor antagonists, directly increasing prolactin secretion.
Hormonal therapies, such as oral contraceptives and hormone replacement therapy, can contribute to nipple discharge. Illicit drugs like marijuana and cocaine can elevate prolactin levels and cause discharge.
Non-Medication Causes of Nipple Discharge
While medications are a significant cause, nipple discharge can arise from many other sources. Hormonal imbalances, such as a noncancerous pituitary tumor (prolactinoma) or an underactive thyroid (hypothyroidism), can lead to elevated prolactin and milky discharge. These conditions disrupt hormone regulation.
Benign breast conditions are common causes of discharge. These include intraductal papillomas (small, noncancerous growths within milk ducts) and mammary duct ectasia (where milk ducts widen and may become inflamed). Breast infections, such as mastitis or abscesses, can also result in nipple discharge, often appearing yellow or pus-like.
Nipple discharge is normal during pregnancy and breastfeeding. Trauma or irritation to the breast, such as from tight clothing or excessive nipple stimulation, can also induce discharge. In rare instances, nipple discharge can be a symptom of breast cancer, particularly if it is bloody, clear, or comes from only one breast spontaneously.
Guidance on Seeking Medical Care
Any new or persistent nipple discharge warrants evaluation by a healthcare professional. Even if a medication is suspected, medical assessment is important to rule out other conditions. When consulting a doctor, provide a comprehensive medical history, including all current medications, supplements, and any recent regimen changes.
Details about the discharge are valuable, such as its color, consistency, whether it comes from one or both breasts, and if it occurs spontaneously or only with stimulation. Mention any accompanying symptoms, like a breast lump, pain, redness, or nipple changes, as these characteristics guide the diagnostic process. A healthcare provider can perform a physical examination and recommend further tests, such as blood work or breast imaging, to identify the cause.