In vivo absorption of aluminium-containing vaccine adjuvants using ²⁶Al

Aluminium hydroxide (AH) and aluminium phosphate (AP) adjuvants, labelled with ²⁶Al, were injected intramuscularly (i.m.) in New Zealand White rabbits. Blood and urine samples were collected for 28 days and analysed for ²⁶Al using accelerator mass spectrometry to determine the absorption and elimination of AH and AP adjuvants. ²⁶Al was present in the first blood sample (1 h) for both adjuvants. The area under the blood level curve for 28 days indicates that three times more aluminium was absorbed from AP adjuvant than AH adjuvant. The distribution profile of aluminium to tissues was the same for both adjuvants (kidney > spleen > liver > heart > lymph node > brain). This study has demonstrated that in vivo mechanisms are available to eliminate aluminium-containing adjuvants after i.m. administration. In addition, the pharmacokinetic profiles of AH and AP adjuvants are different.