4 replies to this topic

[electricbuddha]

Should retin-a be used only on areas of the face that are prone to wrinkles, such as laugh lines or around the eye? Or is it better to use it on one's entire face?

[niner]

My understanding is that retin-A is best used only on the face, but I'm not sure why this should be so. I'll add a question to the above: Can or should Retin-A be used on other parts of the body besides the face? Why or why not?

[mustardseed41]

Should retin-a be used only on areas of the face that are prone to wrinkles, such as laugh lines or around the eye? Or is it better to use it on one's entire face?

Use it on your entire face. You often hear to avoid the eye area but that is foolish to me. That area is most prone to aging. I use it on my lips, neck and hands as well.

Edited by mustardseed41, 11 December 2008 - 11:45 PM.

[kismet]

My understanding is that retin-A is best used only on the face, but I'm not sure why this should be so. I'll add a question to the above: Can or should Retin-A be used on other parts of the body besides the face? Why or why not?

You can use it everywhere you want, but you should not apply to more than a certain surface area to avoid systemic effects.
As far as I understand you could apply retinoids to a much bigger surface than just your face, you'd just need to keep your vitamin A levels in check.
Total body surface area is about 18-20k cm² , so 2300cm² is 12-13% of the area. According to the rule of nines the head will be about 9% of total body area, the face being <4.5cm². So way to go before you'd experience systemic effects.

I don't know what the optimal level of vitamin A is and if going all the way up to the UL of 10'000 IE is still perfectly safe for life extensionists, but assumig it is there is a lot of leeway. Another issue might arise if retinoids convert to more active or not well characterised vitamin A metabolites in vivo, then it could make sense to apply only to the face if you want to be perfectly safe. I don't know if they do, we need to wait for Fredrik to get an answer.

The objective of the study was to assess the extent of systemic exposure of retinoic acid metabolites after excessive application of 0.1% isotretinoin cream in patients with photodamaged skin. This was a single-center, open-label, noncomparative, multiple-dose study of isotretinoin cream. Eighteen female patients with photodamaged skin received a 10 g topical application of isotretinoin cream once daily to a surface area of approximately 2,300 cm2 for 42 days. The patients were not allowed to have high vitamin A-containing foods, vitamin A supplements, or concomitant medications during the entire study period. Plasma levels of four retinoic acids (isotretinoin, tretinoin, 4-oxo-isotretinoin, and 4-oxo-tretinoin) were evaluated after 42 days of isotretinoin application and compared with baseline (pretreatment) levels. The mean area under the curve (AUC) in plasma increased by 48% (+/-SE 9.2) and 77% (+/-13) from the 24-hour pretreatment baseline level for isotretinoin and 4-oxo-isotretinoin, respectively, after treatment with excessive amounts of isotretinoin cream, suggesting systemic absorption of isotretinoin cream. This increase in systemic exposure of retinoic acids was less than that reported earlier after the U.S. recommended daily allowance of 5,000 i.u. of vitamin A supplementation (isotretinoin 141 +/- 19% and 4-oxo-isotretinoin 171 +/- 27%). 

Personally I use retinoids on my face (including chin), scars and striae. Going by this study I could additionally include my palms for instance and might do so in the future if it is perfectly safe...

Edited by kismet, 12 December 2008 - 12:45 AM.

[Fredrik]

Another issue might arise if retinoids convert to more active or not well characterised vitamin A metabolites in vivo, then it could make sense to apply only to the face if you want to be perfectly safe. I don't know if they do, we need to wait for Fredrik to get an answer.

You gave an excellent answer kismet, I would have referred to the same study. I´m sorry to say I don´t have any additional information (I think FDA have pounds of unpublished documentation though. Freedom act!) other than that tazarotene should not be used over more than 20% of the body. This was recommended when it got approved as a psoriasis drug. I would use the same cut off of 20% for tretinoin just to be safe.

I answered a somewhat similar question here with reference to how much retinoids raise levels of retinol, in the blood plasma:

http://www.imminst.o...&...st&p=277427

and kismet posted about negligible systemic absorption of topical isotretinoin in the same post.

Edited by Fredrik, 12 December 2008 - 08:50 AM.