Prescription DHT Blockers: What Do Doctors Prescribe?
What prescription DHT blockers are available?
Strip this category back and there are only two drugs that actually lower DHT, and almost everything else filed under the same heading works a completely different way. That distinction decides what a prescription can and can't do for your hairline, and it decides what you're signing up for long term.
Only the 5-alpha reductase inhibitors finasteride and dutasteride lower DHT directly, cutting circulating levels by around 65 percent and more than 90 percent respectively, and both hold their benefit only for as long as you keep taking them.
Which medications are prescribed specifically to reduce DHT in pattern hair loss?
The list is shorter than most people expect once you sort these drugs by what they actually do. Two molecules cut DHT production, a second group leaves production alone and blocks the receptor instead, and a third group that gets shelved alongside them has no hormonal action at all. Knowing which tier your prescription sits in tells you what to expect from it.
Only finasteride and dutasteride reduce DHT production, while spironolactone, cyproterone acetate and bicalutamide block the androgen receptor instead and oral minoxidil has no hormonal action whatsoever.
How do the two main 5-alpha reductase inhibitors differ in what they actually block?
Both drugs go after the same enzyme, but there are two versions of it and that's the whole difference. Type II sits mainly in the follicle, the prostate and genital skin, while type I is spread through your sebaceous glands, liver and skin generally. One drug takes out half the problem cleanly, the other takes out both and lingers a lot longer while it does.
| Criteria | Finasteride | Dutasteride |
|---|---|---|
| Isoenzymes blocked | Type II only | Type I and type II |
| Serum DHT reduction | About 65 percent | Over 90 percent |
| Hair loss licence | Yes, in most markets | A handful of countries |
| Time to clear your system | A few days | Four to six months |
Finasteride blocks only the type II isoenzyme and clears within days, while dutasteride blocks both isoenzymes, cuts serum DHT by more than 90 percent and can stay detectable in serum for four to six months after the last dose.
What doses are typically prescribed and how are they taken?
One tablet a day, any time of day, with or without food. What trips people up is the strength sitting on the pharmacy shelf, because the common tablet is the prostate dose at five times what a follicle needs. The dose response curve for DHT is steep at the bottom and flat at the top, so pushing the milligrams up when results stall almost never buys you anything.
- Finasteride, hair loss dose: 1 mg daily, timing flexible, consistency matters more than the hour.
- Dutasteride, scalp use: 0.5 mg daily, sometimes two or three times a week.
- Off label dosing in women: 2.5 to 5 mg daily, alongside contraception or confirmed post menopause.
- Missed dose: skip it and never double up; one gap changes nothing.
The hair loss dose of finasteride is 1 mg daily, one fifth of the 5 mg prostate tablet, and raising the dose when results plateau adds little because the DHT dose response curve is already flat at that point.
Are prescription topical formulations a genuine alternative to taking a pill?
A topical isn't a different drug. It's the same molecule mixed by a pharmacy into a solution, gel or foam carrying somewhere between 0.0025 and 0.25 percent finasteride, often with minoxidil in the same vehicle. The evidence is better than sceptics expect and more qualified than the marketing suggests, and the one thing you can't assume is that it all stays on your scalp.
Topical finasteride is a compounded preparation of 0.0025 to 0.25 percent that produced hair counts approaching the 1 mg tablet while reducing serum DHT by about a third rather than half, so it lowers systemic exposure without removing it.
Who can be prescribed these medications and who must avoid them?
Eligibility starts with the diagnosis, not the prescription. A DHT blocker treats androgenetic alopecia and does nothing for telogen effluvium, alopecia areata, scarring alopecia or traction loss, so hair that arrived suddenly and diffusely needs investigating before anyone reaches for a pad. After that, the boundaries are firm and one of them is absolute.
- Pregnancy: absolute contraindication, and the precaution covers handling crushed or broken tablets.
- Women: off label everywhere, generally post menopause or on reliable contraception.
- Under eighteen: no trial support, avoided outside specialist settings.
- Prostate screening: treatment lowers PSA, so the interpreting clinician has to know you're taking it.
These drugs are absolutely contraindicated in anyone who is or may become pregnant because blocking 5-alpha reductase interferes with normal development of the male external genitalia, and that precaution extends to handling crushed or broken tablets.
What side effects are documented and how often do they occur?
You deserve the real numbers here rather than either the horror stories or the breezy reassurance. In the one year trials of finasteride at 1 mg, the sexual side effects people worry about most turned up in a small minority, and the placebo group reported them too, which tells you how much expectation shapes what gets noticed and blamed. A smaller contested group reports symptoms that persist long after stopping, and the evidence there is too weak to put a reliable frequency on it.
| Reported effect | Finasteride 1 mg | Placebo |
|---|---|---|
| Reduced libido | 1.8 percent | 1.3 percent |
| Erectile difficulty | 1.3 percent | 0.7 percent |
| Reduced ejaculate volume | 1.2 percent | 0.7 percent |
| Stopping for any drug related reason | About 1.5 percent | Close to the same |
In the one year finasteride trials reduced libido was reported by about 1.8 percent of men against 1.3 percent on placebo, and for the large majority the symptoms settle either during continued use or within weeks of stopping.
What does a prescribing consultation involve and what monitoring follows?
Most of a prescribing consultation is diagnosis rather than transaction. If you leave without a standardised photograph, the six month review turns into guesswork, because hair changes far too slowly for anyone's memory to judge it.
- Scalp examination: dermoscopy looks for the variation in hair shaft calibre that separates androgenetic miniaturisation from other causes.
- History and pattern grading: onset, rate of change, family pattern, medication, plus anything pointing at thyroid disease, iron deficiency or recent physiological stress.
- Bloods where indicated: ferritin, thyroid function and an androgen screen for diffuse patterns and for women, plus a baseline PSA for men of screening age.
- Baseline photographs: fixed lighting and angle, repeated at every review.
- Counselling and consent: what the drug does, what it won't do, the pregnancy precautions and the side effect profile.
- Review: three to six months for tolerance, twelve months for effect.
Standardised baseline photographs taken under fixed lighting and angle are the most useful thing done at a first consultation, because without them the three, six and twelve month reviews have nothing objective to measure against.
How much regrowth do these medications deliver and how quickly?
Expectations are where nearly all the disappointment in this field starts, so here's what the trials actually counted. The drug's main job is stopping the decline, and regrowth is the secondary bonus that around two thirds of men see to some degree. Timing runs on the hair cycle rather than on your patience.
At twelve months on 1 mg of finasteride men gained an average of about 90 hairs in a one inch vertex circle and around 85 percent avoided further visible loss, with nothing visible before the three month mark.
What do prescription DHT blockers cost over a year of treatment?
The medicine is one of the cheaper things in this field, and the commitment is the expensive part. Almost no insurer and no public health system funds treatment for pattern hair loss because it's classed as cosmetic, so you're paying out of pocket even where the identical drug is fully funded for prostate enlargement. Price the decades, not the month.
Generic finasteride commonly costs 10 to 30 a month and compounded topical preparations 40 to 80, and because pattern hair loss is classified as cosmetic almost no insurer or public health system funds any of it.
What happens to hair if the medication is stopped?
Stopping hands your scalp straight back to your genetics. DHT climbs toward baseline quickly after the last finasteride tablet and over several months for the longer acting drug, and the follicles pick up miniaturising at the rate your genes dictate. Drug holidays buy you nothing here, since there's no tolerance to avoid and no benefit that accumulates through a break.
- First weeks: serum DHT returns toward baseline, fast after finasteride and over months after dutasteride.
- Months 1 to 6: the hair held or regrown during treatment begins shedding.
- Around 12 months: density is back to what it would have been without treatment, and no worse than that.
- Afterwards: loss continues at your natural rate, which can feel like an acceleration because years of gradual change arrive compressed into one.
Hair held or regrown on a DHT blocker is shed over the six to twelve months after stopping, returning you to the density you would have had untreated rather than to anything worse.
