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When applied topically, Rogaine ( minoxidil ) has been shown to stimulate hair growth in males and females
with alopecia androgenetica; however, the exact mechanism of action of Rogaine in the treatment of alopecia
androgenetica is not known. The regrowth can be observed after approximately 4 or more months of use and is
variable among patients. Upon discontinuation of treatment with Rogaine, new hair growth stops and restoration
of pretreatment appearance may occur within 3-4 months.
Topical application of Rogaine showed no systemic effects related to absorption of minoxidil when tested in
controlled clinical trials in both normotensive and untreated hypertensive patients.
Minoxidil administered orally for the treatment of hypertension has a direct peripheral vasodilator effect
which reduces elevated systolic and diastolic blood pressure by decreasing peripheral vascular resistance. Reduction
of peripheral arteriolar resistance and the associated fall in blood pressure induces sympathetic, vagal inhibitory,
and renal homeostatic mechanisms, including an increase in renin secretion, which lead to increased heart rate
and cardiac output, and salt and water retention. Minoxidil does not interfere with vasomotor reflexes and therefore
does not produce orthostatic hypotension. In experimental animals, the drug does not enter the central nervous
system ( CNS ) in significant amounts.
Following topical application, minoxidil is poorly absorbed from normal intact skin, with an average of approximately
1.7% of the total applied dose ultimately reaching the systemic circulation. In contrast, minoxidil is almost
completely absorbed from the gastrointestinal tract following oral administration of minoxidil tablets. Following
cessation of topical dosing of Rogaine approximately 95% of systemically absorbed minoxidil is eliminated within
4 days. The effects of concomitant dermal diseases on absorption are unknown.
The metabolic biotransformation of minoxidil absorbed following topical application has not been fully determined.
The active form of the drug appears to be a sulfated metabolite, minoxidil sulfate. Orally administered minoxidil
is metabolized predominantly by conjugation with glucuronic acid at the N-oxide position in the pyrimidine ring
but also by conversion to more polar products. Minoxidil does not bind to plasma proteins and its renal clearance
corresponds to the glomerular filtration rate. Minoxidil does not cross the blood brain barrier. Minoxidil and
its metabolites are hemodialyzable, and are excreted principally in the urine.
In 2326 adults with early male pattern baldness who applied 1mL of 2% topical solution on the scalp twice daily
for 12 months, cosmetically acceptable hair growth was observed in only a small % of individuals. Dense hair
growth occurred in only 8% of individuals. Moderate hair growth was observed in a further 30% of subjects.
Two studies in healthy males aged 18-50 years with androgenetic alopecia showed statistically significant differences
favoring 5% over 2% topical solution with regard to non-vellus hair counts. Compared to mean baseline counts
of 103-106/cm2, at the end of 32 weeks treatment mean increases in non-vellus hair counts were 39/cm2 in subjects
who received 5% topical solution ( N=163 ), 30/cm2 in subjects who received 2% topical solution ( N=79 ), and
5/cm2 in subjects who received placebo ( N=79 ). In the other study, compared to mean baseline counts of 144-152
/cm2, at the end of 48 weeks treatment mean increases in non-vellus hair counts were 19/cm2 in subjects who
received 5% topical solution ( N=137 ), 13/cm2 in subjects who received 2% topical solution ( N=139 ), and 4/cm2
in subjects who received placebo ( N=70 ).
Two studies in healthy females aged 18 to 50 years with adrogenetic alopecia showed statistically significant
differences favoring 5% over placebo, but not over 2% topical solution with regard to non-vellus hair counts.
Compared to mean baseline counts of 178-185 /cm2, at the end of 36 weeks treatment mean increases in non-vellus
hair counts were 18/cm2 in subjects who received 5% topical solution ( N=64 ), 15/cm2 in subjects who received
2% topical solution ( N=74 ) and 3/cm2 in subjects who received placebo ( N=40 ). In the other study, compared
to mean baseline counts of 138-150/cm2, at the end of 48 weeks treatment mean increases in non-vellus hair counts
were 25/cm2 in subjects who received 5% topical solution ( N=97 ), 21/cm2 in subjects who received 2% topical
solution ( N=106 ), and 9/cm2 in subjects who received placebo ( N=50 ).
Examination of efficacy data based on hair weight measurements demonstrated an overall clinical benefit of
5% topical solution and 2% topical solution in stimulating hair growth. Additionally, this study strongly demonstrated
the stabilization of hair loss over the 2 year treatment period.
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