Letters t o the Editor


Minimizing Pain Due to Local Anesthesia To the Editor: Minimizing pain due to injection of local anesthetics is foremost in the minds of most dermatologic surgeons. The study by Stewart et al., along with editorial comment by Skouge, in the October 1989 issue furthers our attempt to address this aggravating problem. An alternative to modifying lidocaine solutions by adding a buffering agent is to follow the technique that I described for anesthetizing the scalp for hair transplant surgery: ”Three factors contribute to the pain of local anesthesia: (1)needle size, (2) rapidity of injection, and (3) the pH of the anesthetic. The local anesthesia is accomplished in two steps: plain lidocaine followed by lidocaine with epinephrine. The donor site is anesthetized with lidocaine 2% without epinephrine after each injection is sprayed with ethyl chloride. A 30-gauge needle is used, and the anesthetic is injected very slowly. Lidocaine without epinephrine has a pH of between 6.6 and 6.8.20 This solution can be injected slowly without producing much discomfort. After the area is anesthetized, a second injection of the area is done with lidocaine 2% with epinephrine 1:100,000 to obtain the benefit of vasoconstriction. Because this solution is quite acidic (pH 4.6), injection into a nonanesthetized site would be quite painful. Approximately 10-15 minutes is required for full vasoconstriction before grafts are taken.”’ This method of injecting local anesthetics has served my practice well. It relieves me of having to track the degradation factors in buffered or modified solutions of lidocaine. W. R O Y KNOWLES, M.D. Hoirstoii, Texns

REFERENCE 1 . Knowles WR. Hair transplantation: A review. Dermatol Clin Vol 5 , July 1987.

Stability Study of Trichloroacetic Acid To the Editor: The stability study of trichloroacetic acid solutions (TCA) in a recent issue of the Iournal (15:974-975, 1989) will lay to rest some misconceptions, such as the commonly held view that such preparations should be prepared fresh for maximum potency, or the unsubstantiated statement in Merck Index stating that ”storage of trichloroacetic acid in water at concentrations below 30% are not recommended.” Unfortunately, there were several concepts that were not studied or were studied improperly. Because of this, the reader could reasonably arrive at unproven, erroneous conclusions. The study suggested that TCA stability was best in amber bottles. Trichloroacetic acid is not listed as light sensitive by the United States Pharmacopoeia, the Merck Index, or the manufacturer’s material data safety sheet. Yet, the authors chose to use only light-resistant (amber) bottles in their study. Whereas the results clearly indicated that lightresistant glass bottles retained stability of several dilutions of TCA, it did not demonstrate any instability in clear bottles, nor is there any reference cited to support such a recommendation. Further, the study purported to compare stability of TCA in glass as opposed to ”plastic.” Unfortunately, one of the few plastic materials that is not resistant to TCA, polycarbonate (of which prescription-type liquid containers are composed), was chosen for the comparison. Of course, the containers dissolved. The obvious conclusion is that ordinary ARQ


plastic prescription containers must not be used to contain TCA. The most logical approach at this point would have been to use a TCA-resistant plastic, if one of the purposes of the study was to compare stability in glass versus plastic. Because there are specific advantages of plastic versus glass, it seems inappropriate to dismiss the possibility of using plastic. A TCA-resistant plastic has the obvious advantage of being unbreakable. This is not only advantageous in the office, but if any transport is required, a broken glass bottle can result in significant damage before discovery. Glass bottles generally have a wax-covered paper seal/lining for the cap. This paper is susceptible to the action of TCA, and can result in an imperfect seal, with subsequent subliminal loss of the TCA and/or absorption or evaporation of water. Plastic containers, where all parts of the bottle, cap, and seal are TCA-resistant, are available. There is also an advantage to having the TCA in a clear container (glass or plastic). Any discoloration suggestive of contamination or deterioration is immediately apparent in clear containers, whereas it may be masked in amber containers. JAMES F. DOLEZAL, R.PH., M.D. Council Bluffs, lowa

Drs. Rumsfield and Spinowitz Reply To the Editor: We would like to thank Dr. James Dolezal for his interest in our article (15:974-975, 1989). The objectives of our study were to determine the stability, shelf-life, and proper storage of stock bottles of trichloroacetic acid solution (TCA) under the most common conditions. Many dermatologists purchase extemporaneously prepared stains and other stock solutions from their local pharmacies. Stability of solutions in this situation was of most interest for study since solutions purchased from proprietary sources would by federal Good Manufacturing Practices already be tested for stability and expiration dating. Our selection of bottles and storage conditions was based on what materials and conditions are available to the majority of pharmacies and dermatologists. Most pharmacies stock amber glass versus clear glass bottles to provide for a wider range of stability and to limit inventory. Usage of clear glass bottles was initially considered in this study but was excluded due to budgetary and time constraints. The plastic bottles selected for the study were also obtained from a major pharmacy distributor, Brockway Plastics, Ohio. These bottles


exemplify bottles commonly found in pharmacies and are made of low-density polyethylene tetrathalate (not of polycarbonate, which Dr. Dolezal incorrectly concluded). We felt that reporting our findings of the TCA solution dissolving such commonly available plastic containers was important to both dermatologists and pharmacists not familiar with such compounding pitfalls. The exact type of plastic used in our study was not initially reported and we regret any confusion this may have caused. In response to other comments and conclusions from Dr. Dolezal about our study, due to a limited budget, every possible situation could not be investigated. It would be improper to make conclusions based on parameters that we did not, or were not, able to specifically study. The purpose of this study was to provide guidelines for the practitioner who uses extemporaneously compounded TCA solutions. Dermatologists should be aware of the fact that ethical proprietary manufacturers of such stock solutions should be regulated by federal Good Manufacturing Practice to ensure that products are tested for stability and expiration in the containers in which they are to be marketed and shipped. Therefore, the results of our study should not be extrapolated to products that are commercially available from ethical sources. JEAN RUMSFIELD, PHARM. D. Chicago, Zllinois ALAN L. SPINOWITZ, M.D. East Meadow. New York

CO, Laser Treatment of Erythroplasia of Queyrat To the Editor: Erythroplasia of Queyrat is traditionally a difficult therapeutic problem for which major disfiguring and functionally distorting surgery used to be performed. Any conservative method of treatment must be welcome, and success with the laser is a valuable contribution to management of these patients, as described in a recent article in the JournaZ (15:747-750, 1989). However, it is not widely available, and is rather more expensive than some of the alternative therapies that have been shown to be effective. We would like to remind clinicians that a very cheap and simple method of treatment is available. Cryosurgery is readily used to treat Bowen’s disease on other areas of the body leaving good cosmetic scarring without contracture of the skin.’ Two freeze-thaw cycles of 30 seconds using a liquid nitrogen spray are sufficient to clear Bowen’s disease in any site including the vulva,2 perineum,’ and penis (erythroplasia of Q ~ e y r a t ) . ~ J Dermatol Sirrg Oncol 16:5 May 1990

Stability study of trichloroacetic acid.

Letters t o the Editor DEPARTMENT Minimizing Pain Due to Local Anesthesia To the Editor: Minimizing pain due to injection of local anesthetics is fo...
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