Tretinoin(tret' i noe in) | Retin A |
| Category | Collagen booster |
| Parameter |
Effect |
Result on hair growth |
| DHT |  | UNKNOWN |
| 5a-reductases | | UNKNOWN |
| PGD2 | | UNKNOWN |
| PGE2 | | UNKNOWN |
| PGF2 | | UNKNOWN |
| CRTH2 | | UNKNOWN |
Information
| Description |
Tretinoin is a derivative of vitamin A and used on the scalp topically or mixed with other topicals such as Minoxidil. Tretinoin irritates the skin and causes the cells of the skin to grow and divide and die more rapidly, increasing the turnover of cells.
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| Typical Results |
When used in conjuction with Minoxidil it provides better results than Minoxidil alone.
|
| Typical Dosages |
Pea size amount daily
|
| Significant Side Effects |
Scalp irritation
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| Pharmacology Pharmacodynamics |
Tretinoin is an endogenous retinoid metabolite of Vitamin A that binds to intracellular receptors in the cytosol and nucleus, but cutaneous levels of tretinoin in excess of physiologic concentrations occur following application of a tretinoin-containing topical drug product. Although tretinoin activates three members of the retinoic acid (RAR) nuclear receptors (RARα, RARβ, and RARγ) which may act to modify gene expression, subsequent protein synthesis, and epithelial cell growth and differentiation, it has not been established whether the clinical effects of tretinoin are mediated through activation of retinoic acid receptors, other mechanisms such as irritation, or both.
The effect of tretinoin on skin with chronic photodamage has not been evaluated in animal studies. When hairless albino mice were treated topically with tretinoin shortly after a period of UVB irradiation, new collagen formation was demonstrated only in photodamaged skin. However, in human skin treated topically, adequate data have not been provided to demonstrate any increase in desmosine, hydroxyproline, or elastin mRNA. Application of 0.1% tretinoin cream to photodamaged human forearm skin was associated with an increase in antibody staining for procollagen I propeptide. No correlation was made between procollagen I propeptide staining with collagen I levels or with observed clinical effects. Thus, the relationships between the increased collagen in rodents, increased procollagen I propeptide in humans, and the clinical effects of tretinoin have not yet been clearly defined.
Tretinoin was shown to enhance UV-stimulated melanogenesis in pigmented mice. Generalized amyloid deposition in the basal layer of tretinoin-treated skin was noted in a two-year mouse study. In a different study, hyalinization at tretinoin-treated skin sites was noted at doses beginning at 0.25 mg/kg in CD-1 mice.
The transdermal absorption of tretinoin from various topical formulations ranged from 1% to 31% of applied dose, depending on whether it was applied to healthy skin or dermatitic skin. No percutaneous absorption study was conducted with RENOVA 0.02% in human volunteers. When percutaneous absorption of the oil-in-water emulsion formulation at 0.05% concentration was assessed in healthy male subjects with radiolabeled cream after a single application (n=7), as well as after repeated daily applications (n=7) for 28 days, the absorption of tretinoin was less than 2% and the extent of bioavailability was less after repeated application. No significant difference in endogenous concentrations of tretinoin was observed between single and repeated daily applications.
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Clinical Studies
| Clinical Studies | Abstract |
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Efficacy of 5% minoxidil versus combined 5% minoxidil and 0.01% tretinoin for male pattern hair loss: a randomized, double-blind, comparative clinical trial.
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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.
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Topical tretinoin for hair growth promotion.
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Topical all-trans-retinoic acid (tretinoin) alone and in combination with 0.5% minoxidil has been tested for the promotion of hair growth in 56 subjects with androgenetic alopecia. After 1 year, the combination of topical tretinoin with 0.5% minoxidil resulted in terminal hair regrowth in 66% of the subjects studied. Tretinoin was shown to stimulate some hair regrowth in approximately 58% of the subjects studied. One female subject with pronounced alopecia for more than 20 years had regrowth of hair using only tretinoin for a period of 18 months. Tretinoin has been shown to promote and regulate cell proliferation and differentiation in the epithelium and may promote vascular proliferation. These factors are important for hair growth promotion. These preliminary results indicate that more work should be done on the role of retinoids in hair growth. The synergistic effect of retinoids in combination with a low concentration of minoxidil should also be further investigated.
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