Assessment of Dermal Absorption of Aluminum from a Representative Antiperspirant Formulation Using a (26)Al Microtracer Approach

A clinical pharmacokinetic study was performed in 12 healthy women to evaluate systemic exposure to aluminum following topical application of a representative antiperspirant formulation under real‐life use conditions. A simple roll‐on formulation containing an extremely rare isotope of aluminum ((26)Al) chlorohydrate (ACH) was prepared to commercial specifications. A (26)Al radio‐microtracer was used to distinguish dosed aluminum from natural background, using accelerated mass spectroscopy. The (26)Al citrate was administered intravenously (i.v.) to estimate fraction absorbed (F(abs)) following topical delivery. In blood samples after i.v. administration, (26)Al was readily detected (mean area under the curve (AUC) = 1,273 ± 466 hours×fg/mL). Conversely, all blood samples following topical application were below the lower limit of quantitation (LLOQ; 0.12 fg/mL), except two samples (0.13 and 0.14 fg/mL); a maximal AUC was based on LLOQs. The aluminum was above the LLOQ (61 ag/mL) in 31% of urine samples. From the urinary excretion data, a conservative estimated range for dermal F(abs) of 0.002–0.06% was calculated, with a mean estimate of 0.0094%.