Can anyone tell me the dosage guidelines when applying topical BLT? When treating large areas, it is difficult to determine a safe toxicity level.

Hi Tom,
I've applied to the face and chest for 90 minutes with saran wrap occlusion prior to ablative laser. I would not do this on legs or on a larger surface area than I've described. I've had some patients get mild shakes (early toxicity )
with this but this has been rare.

My guidelines: using rule of 9's for surface area. no more than 18%, ie 2 areas, and i never occlude. I have never had problems and I use a 23%/7% lido - tetracaine topical..

Also Tom, I am only doing this for CO2 and not for other laser treatments.

As an anesthesiologist I am quite aware of local anesthetic toxicity regarding topicals. When they are compounded it becomes harder to obtain real study data regarding absorption vs surface area. If you look up emla cream it gives a very good guide to the recommended surface area and the absorption over time.J eff is correct in using the 18% rule and likely that's still a large surface area. Should it get on any mucous membrane then the absorption is even greater and faster.

The recommended time for triple cream is no longer than 40min. The signs of toxicity are as follows, development of tinnitus , numb lips, dizziness, should the levels really go high seizures and arrythmias. The later should not happen if you keep surface area in mind and wash off the tlc in about 40min. Occlusion dressing started when we needed to use emla on the dorsum of a childs hand for IV insertion. As in the case of a child to big to mask yet to young to cooperate for an IV. When large areas get wrapped the risk of toxicity rises significantly.
I also try to avoid the TLC creams and use either 20% lido sometimes 7%, its safer and it works for the time frame we need, an hour or less. The marcaine starts to work late and lasts a few hours tops, tetracaine probably doesnt even begin to work unitl 20 min ( an educated guess, but its longer than lido) and will last several hours possibly as long as marcaine. But both will do little for a quick laser procedure.
Hope this helps