BACKGROUND: 5% topical minoxidil solution has been widely used to stimulate new 
hair growth and help stop hair loss in men with androgenetic alopecia (AGA). 
However, it is not convenient for patients to continue applying the solution 
twice daily on a regular basis. Tretinoin is known to increase the percutaneous 
absorption of minoxidil and, therefore, to enhance the response of AGA to 
minoxidil. For this reason, it was assumed that tretinoin would be helpful in 
alleviating the inconvenience associated with the recommended twice-daily 
application of minoxidil.
OBJECTIVE: To compare the efficacy and safety of therapy using a combined 
solution of 5% minoxidil and 0.01% tretinoin once daily with those of the 
conventional 5% topical minoxidil therapy applied twice daily in the treatment 
of AGA.
METHODS: A total of 31 male patients (aged 28-45 years, mean 39.7+/-4.5) with 
AGA (Hamilton-Norwood classification type III-V) were randomly assigned into two 
groups, one in which 5% minoxidil was applied to the scalp twice daily and the 
other in which the combined agent was applied once daily at night together with 
a vehicle placebo in the morning. The efficacy parameters were: (i) changes in 
total hair count, non-vellus hair count, anagen hair ratio, linear hair growth 
rate, and mean hair diameter assessed by macrophotographic image analysis; and 
(ii) the patient's and investigator's subjective assessments.
RESULTS: After therapy, increases in the macrophotographic variables of total 
hair count and non-vellus hair count were shown in both treatment groups. There 
were no statistically significant differences between the two treatment groups 
with respect to changes in macrophotographic variables or scores on subjective 
global assessments by patients and the investigator. The incidence of adverse 
effects such as pruritus or local irritation was similar in the 5% minoxidil 
group (4 of 14 subjects) and the combined agent group (5 of 15 subjects).
CONCLUSION: The efficacy and safety of combined 5% minoxidil and 0.01% tretinoin 
once-daily therapy appear to be equivalent to those of conventional 5% minoxidil 
twice-daily therapy for the treatment of AGA.