What causes male breast itching after using Finasteride (finasteride)?

From the Guidelines

If you're experiencing breast itching after using finasteride, you should consult your healthcare provider as this could be a side effect of the medication, with gynecomastia occurring in 4.1% of men taking finasteride, as reported in the PCPT study 1. Finasteride, commonly prescribed at 1mg daily for hair loss or 5mg for prostate conditions, can occasionally cause breast-related side effects including tenderness, enlargement (gynecomastia), and itching in some men. These effects occur because finasteride reduces dihydrotestosterone (DHT) while potentially causing a relative increase in estrogen levels, which can stimulate breast tissue. Some key points to consider about finasteride's side effects include:

• Gynecomastia: Finasteride has been associated with an increased risk of gynecomastia, with a relative risk of 2.13 compared to placebo, as seen in the study 1.
• Decreased libido: Finasteride has also been linked to decreased libido, with 48.5% of men experiencing this side effect in the study 1.
• Other side effects: Other side effects of finasteride include impotence, decreased ejaculate volume, and increased urinary frequency, although these are less common. Don't stop taking finasteride abruptly, but schedule an appointment with your doctor who may recommend adjusting your dosage, switching medications, or ordering tests to rule out other causes. While waiting for your appointment, avoid scratching the area and consider using a mild, fragrance-free moisturizer for temporary relief. Most breast-related side effects resolve after discontinuation of the medication, but proper medical evaluation is important to ensure there are no other underlying issues. It's also important to note that the treatment duration for finasteride can vary, but the PCPT study suggests that a 7-year treatment duration may be necessary for the best outcome in terms of preventing prostate cancer 1.

From the FDA Drug Label

• hypersensitivity reactions, such as pruritus, urticaria, and angioedema (including swelling of the lips, tongue, throat, and face) The FDA drug label mentions pruritus (itching) as a hypersensitivity reaction that has been reported in postmarketing experience with finasteride tablets 2.

• Male breast itching can be considered a related symptom to pruritus. However, the label does not provide direct information on the incidence or prevalence of male breast itching specifically. Therefore, a conservative clinical decision would be to monitor for any signs of hypersensitivity reactions, including itching, and consult a healthcare professional if symptoms persist or worsen.

From the Research

Male Breast Itching after Using Finasteride

• Male breast itching is not directly mentioned in the provided studies as a side effect of finasteride.
• However, gynecomastia, which is the enlargement of breast tissue in men, is reported as a rare side effect of finasteride in one of the studies 3.
• Gynecomastia can cause breast tenderness, swelling, and itching, but it is not explicitly stated in the studies whether finasteride causes breast itching.
• The studies primarily focus on the efficacy and safety of finasteride in treating benign prostatic hyperplasia (BPH) and its comparison with other medications such as dutasteride 4, 5, 6.
• Finasteride is also known to cause other side effects such as ejaculation disorder, impotence, and lowered libido, but breast itching is not mentioned as a common side effect 4, 7.