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Phenol-Croton Oil Peels
Introduction
The history of phenol–croton oil peels dates back to the 1920s, when they were introduced into the United States by “lay peelers” coming from Europe. The formulas involved boiling crystals to obtain liquid phenol, to which were added drops of the caustic acid croton oil, among other ingredients. How these original formulas came to be is unknown, but what is clear is that the treatments were quite effective. Eventually these peels came to the attention of the medical community, and in 1961, plastic surgeon Thomas Baker from Miami published a formula that was straightforward and easily reproduced. The formula contained liquid phenol, three drops of croton oil, water, and the surgical soap Septisol, which acted as a surfactant to allow the aqueous and oily parts to mix. The belief at the time was that the phenol was the peeling agent and the purpose of the croton oil was unclear.
In 1962, Dr. Baker altered the volumes of the ingredients but left the three drops of croton oil unchanged. This simple change raised the concentration of the croton oil to 2.1% and became the standard formula, unchanged for decades. This peel was highly effective in treating deep wrinkles, but this was always at the cost of creating significant hypopigmentation and an unnatural alabaster look. Due to the need to constantly wear makeup, this peel was reserved for older, significantly wrinkled individuals with light eyes.
The peel was considered difficult to perform, and phenol had the reputation of having an “all-or-none” quality that was out of the practitioner’s control. A weaker concentration of phenol was thought to be problematic, because it would peel deeper, and phenol also had the reputation of being cardiotoxic. These beliefs became ingrained in the fields of dermatology and plastic surgery and went unchallenged for decades. Despite the remarkable results, the risks were too intimidating, and “phenol peels” did not see widespread acceptance.
The next significant step in the evolution of the peels was brought about by plastic surgeon Gregory Hetter in Las Vegas. Hetter experimented with the ingredients of the Baker peel and convincingly proved that croton oil and not phenol was the peeling agent. Moreover, the Baker formula contained a high concentration of croton oil at 2.1%, responsible for the results and the feared complications. With this information, the croton oil concentration could be manipulated to be clinically effective while avoiding hypopigmentation. An important difference is that the peel could be performed superficial or deep, increasing the versatility.
The ability to alter the croton oil concentration has great utility and completely changes the nature of the peel. By using weaker croton oil concentrations the application technique becomes one of the important factors in determining the depth reached. The entire process is slowed down, and now the surgeon can observe the skin changes and have the opportunity to stop at whatever depth seems appropriate. The all-or-none phenomenon seen with the Baker peel was simply that the croton oil concentration was so high that it immediately resulted in a peel deep enough to cause hypopigmentation. The peel can now be customized, and by choosing the appropriate concentration and how the solution is applied, the practitioner is in precise control.
It is now feasible to peel to the desired clinical result without reaching a depth that causes hypopigmentation. A critical difference is that now the practitioner can choose different concentrations on different areas of the face depending on need and relative skin thickness. The Baker formula was all one high concentration, and many practitioners were reluctant to treat the eyelids because of fear of scarring. With the modern formulas, a weak concentration such as 0.1% can now safely and effectively treat the eyelid skin.
During my career as a plastic surgeon, the term “comprehensive facial rejuvenation” is frequently mentioned as an idealized goal. An excellent facelift that leaves prominent lip lines and an etched periorbital area is an aesthetic failure. Now at last there is an excellent tool available for facial resurfacing; the goal is to understand the process, simplify the delivery, and explore the potential.
Patient Selection
As a plastic surgeon, I have historically promoted surgery, but now that I have a viable option, I have learned that many patients place greater importance on the overall appearance of their skin and may be satisfied by a peel alone. Lighter peels that can be done on younger patients to target pigmentation and segmental peels, particularly around the eyes, are a useful adjunct to treatment plans. The main contraindication is a patient who is expected to be uncooperative in the postoperative care and may not refrain from picking. A relative contraindication is a patient whose skin is severely sun damaged and judged to be fragile. Staged lighter peels may be an option in these situations.
Preoperative Planning
Preparation of the skin before the peel is done to prevent hyperpigmentation and put the skin in a hyperproliferative state. The treatment begins 4 to 6 weeks before peeling, with tretinoin 0.05% or 0.1% and hydroquinone 4% twice daily (see Chapter 3 ). An exfoliating agent such as glycolic acid or phytic acid may be used to remove desquamated cells. The preparation is stopped 4 to 5 days before the peel to allow the epidermis to normalize. There is controversy whether this skin preparation is absolutely necessary, but my recommendation is to use it, especially in darker-skinned individuals.
Preparation of the Solution
The preparation of the acid solutions is a critical step that should be performed by the operator. The ingredients are the same as the Baker peel and consist of water, phenol, croton oil, and Septisol/Novisol.
Liquid phenol is 88% or 89%, and its corrosive effect allows passage into the dermis.
Croton oil is extracted from the seeds of Croton Tiglium , a tree indigenous to Asia. Full-strength croton oil is highly caustic and will result in a full-thickness burn if applied to the skin. However, when correctly diluted and appropriately applied, croton oil will yield remarkable aesthetic improvement.
Septisol is a surgical soap that has been historically used as a surfactant to allow miscibility of the aqueous and oil components. Septisol contains triclosan as a preservative, and this has become problematic as of late. Safety issues regarding triclosan have been raised resulting in a ban of Septisol in Europe and more recently by the Food and Drug Administration (FDA) in the United States. The triclosan is inconsequential to the peel, but the reality is that Septisol is no longer available.
Pure soaps may work, but recent work by Young Pharmaceuticals (Wethersfield, CT) has resulted in a viable alternative for Septisol and further understanding into the role of the surfactant. The necessity of replacing Septisol may have brought about an unexpected improvement.
Analysis of Septisol as a surfactant shows that it is an anionic detergent and results in a cruder, larger particle emulsion. The action of this emulsion is that the ingredients separate within seconds and a gradient forms. As the solution is applied, there may be different concentrations presented across the gauze leading to uneven action. The solutions need to be constantly shaken to try to mix the ingredients as best as possible.
The product that has been developed (Novisol) is a nonionic detergent that yields an emulsion of smaller particle size leading to a much more stable suspension. Once shaken, the ingredients mix evenly and stay in suspension during the entire course of the peel. As the solution is applied, the concentration is unchanged across the gauze and ultimately it is an improved product.
The ingredients are arranged in glass bowls in the order they will be added, and this routine should be repeated every time to prevent confusion. Once prepared, the acids can be stored in opaque bottles with leak-proof caps for extended periods of time.
The original Baker formulas were based on drops of croton oil. Droppers have the disadvantage of variability in the volume of drops and limiting the possible concentrations by the inability to split a drop. Hetter simplified the process of creating a standard phenol–croton oil solution using larger volumes, which would then be further diluted with the other ingredients ( Table 7.1 ). The standard solution, or “stock solution,” is prepared by mixing 24 mL of 88% phenol and 1 mL of croton oil. Eighty-nine percent phenol can be used without appreciable difference. Using larger volumes allows easy measurement with standard syringes and avoids the awkwardness of drops.
TABLE 7.1
Formulas With 35% Phenol Concentration
| 0.2% | 0.4% | 0.8% | 1.2% | |
|---|---|---|---|---|
| Water | 5.5 mL | 5.5 mL | 5.5 mL | 5.5 mL |
| Surfactant (i.e., Novisol) | 0.5 mL | 0.5 mL | 0.5 mL | 0.5 mL |
| USP phenol 88% | 3.5 mL | 3.0 mL | 2.0 mL | 1.0 mL |
| Stock solution (containing phenol and croton oil) | 0.5 mL | 1.0 mL | 2.0 mL | 3.0 mL |
| Total volume | 10 mL | 10 mL | 10 mL | 10 mL |
| Stock Solution: 24 mL USP 88% Phenol + 1 mL croton oil (0.04 mL croton oil/1 mL stock solution or 4% croton oil) Dilute formulas with 35% phenol concentration:
Phenol Solution for Preliminary Anesthesia
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Standard tables further delineate the specific volumes of each ingredient needed to arrive at a specific croton oil concentration. The phenol concentration in these formulas as devised by Hetter is approximately 35% in contrast with the Baker formula that was 50%.
In the croton oil concentration of 0.2%, 0.4%, 0.8%, and 1.2% listed in Table 7.1 , the volumes of water and surfactant remain constant at 5.5 mL and 0.5 mL, respectively. The values that change are the relative volumes of phenol and stock solution (which contains phenol and croton oil). The sum of the volumes of phenol and stock solution is 4 mL in each of the formulas.
To better understand the basis of these formulas, it is valuable to examine them more closely. The stock solution consists of 24 mL of phenol and 1 mL of croton oil. Each 1 mL of stock solution has 0.04 mL of croton oil, or a 4% croton oil solution. For example, the formula for 0.8% croton oil is made up of 5.5 mL of water, 0.5 mL of surfactant, 2.0 mL of phenol, and 2.0 mL stock solution. The 2.0 mL of stock solution contains 0.08 mL of croton oil (2 x 0.04 mL). As the total volume of the solution is 10 mL, the final concentration of croton oil is 0.08 mL of croton oil in 10 mL total volume, or 0.8%. By comparing the volume of stock solution in any of the formulas with the known content of croton oil in the stock solution, the final concentration of croton oil can easily be determined. It is important to note that the concentration of croton oil in the stock solution is extremely high at 4% and should never be applied to the skin without further dilution.
To make weaker concentrations, 0.4% or 0.2% are first mixed and these are further diluted using the formulas in Table 7.1 . The final volume is 4 mL and the phenol concentration is kept at 35%. Whatever starting concentration is used with this dilution formula will be diluted by one fourth, or 1ml X% solution + 1.2 mL phenol + 1.8 mL water will yield 0.025% solution.
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