Side effects are the biggest concern for men considering hair loss medication. Online forums can amplify fears, so it is important to look at what large-scale clinical trials and MHRA post-marketing data actually show about the risks.
Finasteride Side Effects
The most discussed side effects of finasteride 1 mg are sexual in nature. In the pivotal clinical trials submitted to the MHRA, the following rates were reported versus placebo:
- Decreased libido: 1.8% (finasteride) vs 1.3% (placebo)
- Erectile dysfunction: 1.3% vs 0.7%
- Ejaculation disorder: 1.2% vs 0.7%
These differences are statistically modest. Importantly, most men who experienced sexual side effects found that they resolved upon discontinuation, and in many cases resolved even with continued use.
A study in the Journal of Sexual Medicine (2007) found a significant nocebo effect — men informed about potential sexual side effects before starting finasteride were more likely to report them than those who were not informed.
Minoxidil Side Effects
Because minoxidil is applied topically, its side effects are predominantly local:
- Scalp irritation, dryness, and flaking — the most common complaint, often caused by the propylene glycol in the liquid formulation
- Initial shedding — temporary increased hair fall in the first 2 to 8 weeks, which is a normal part of the treatment process
- Unwanted facial hair growth — can occur if the solution migrates to the face during sleep
- Dizziness or light-headedness — rare with topical use, but possible given minoxidil's blood-pressure-lowering origins
Switching from the liquid to the foam formulation often resolves scalp irritation issues.
Post-Finasteride Syndrome
Some men report persistent sexual or psychological symptoms after stopping finasteride, referred to as post-finasteride syndrome (PFS). The MHRA acknowledges reports of persistent effects in the patient information leaflet. However, PFS remains an area of active research, with no consistent biological mechanism established to date. Men who experience persistent symptoms should consult their GP.
When to Seek Medical Advice
If you experience any side effects that concern you, speak to your prescriber or pharmacist. Most side effects from hair loss treatments are mild and reversible. Your prescriber can help you weigh the benefits of continued treatment against any side effects you are experiencing. Never stop a prescribed medication without first consulting a healthcare professional.