§352.73. Determination of SPF value. — Inbound Citations

(6) Begin solar simulator exposure to test site areas as described in § 352.73.

(b) A series of UV radiation exposures expressed as Joules per square meter (adjusted to the erythema action spectrum calculated according to § 352.73(a)) is administered to the subsite areas on each subject with an accurately calibrated solar simulator. A series of five exposures shall be administered to the untreated, unprotected skin to determine the subject's inherent MED. The doses selected shall be a geometric series represented by (1.25 n), wherein each exposure time interval is 25 percent greater than the previous time to maintain the same relative uncertainty (expressed as a constant percentage), independent of the subject's sensitivity to UV radiation, regardless of whether the subject has a high or low MED. Usually, the MED of a person's unprotected skin is determined the day prior to testing a product. This MED(US) shall be used in the determination of the series of UV radiation exposures to be administered to the protected site in subsequent testing. The MED(US) should be determined again on the same day as the standard and test sunscreens and this MED(US) should be used in calculating the SPF.

(d) Use data from at least 20 test subjects with n representing the number of subjects used. First, for each subject, compute the SPF value as stated in § 352.73(b) and (c). Second, compute the mean SPF value, x , and the standard deviation, s, for these subjects. Third, obtain the upper 5-percent point from the t distribution table with n-1 degrees of freedom. Denote this value by t. Fourth, compute ts/ √n. Denote this quantity by A (i.e., A = ts/ √n). Fifth, calculate the SPF value to be used in labeling as follows: the label SPF equals the largest whole number less than x . - A. Sixth and last, the drug product is classified into a PCD as follows: if 30 + A <x , the PCD is High; if 12 + A <x <30 + A, the PCD is Moderate; if 2 + A <x <12 + A, the PCD is Minimal; if x <2 + A, the product shall not be labeled as a sunscreen drug product and shall not display an SPF value.

(d) Use data from at least 20 test subjects with n representing the number of subjects used. First, for each subject, compute the SPF value as stated in § 352.73(b) and (c). Second, compute the mean SPF value, x , and the standard deviation, s, for these subjects. Third, obtain the upper 5-percent point from the t distribution table with n-1 degrees of freedom. Denote this value by t. Fourth, compute ts/ √n. Denote this quantity by A (i.e., A = ts/ √n). Fifth, calculate the SPF value to be used in labeling as follows: the label SPF equals the largest whole number less than x . - A. Sixth and last, the drug product is classified into a PCD as follows: if 30 + A <x , the PCD is High; if 12 + A <x <30 + A, the PCD is Moderate; if 2 + A <x <12 + A, the PCD is Minimal; if x <2 + A, the product shall not be labeled as a sunscreen drug product and shall not display an SPF value.