Assessment of Dermal Absorption of Aluminum from a Representative Antiperspirant Formulation Using a 26Al 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 (Al-26) chlorohydrate (ACH) was prepared to commercial specifications. A Al-26 radio-microtracer was used to distinguish dosed aluminum from natural background, using accelerated mass spectroscopy. The Al-26 citrate was administered intravenously (i.v.) to estimate fraction absorbed (F-abs) following topical delivery. In blood samples after i.v. administration, Al-26 was readily detected (mean area under the curve (AUC) = 1,273 +/- 466 hoursxfg/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%.