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Appendices 1-18 to: Report on the Health Effects of Selected Pesticide Coformulants

41  Toxicokinetics

41.1   Absorption, distribution and elimination

Four monkeys were exposed for 5 seconds to the aerosols of an antiperspirant spray containing C¹⁴-labelled isopropyl myristate (the dose was not stated). Labelled material was mainly found in the lungs. Very little systemic absorption (0.25 %) occurred. About 85 % of the absorbed dose was eliminated in 24 hours, mainly as exhaled carbon dioxide. (Finkelstein & Wulf 1974 – quoted from BIBRA 1988, CIR 1982 and IUCLID 2000).

Whole body auto-radiography of hairless mice showed no visible penetration into the skin or organs of isopropyl myristate, whereas microautoradiography of angora rabbits and guinea pigs showed local penetration following dermal application. Whole body auto-radiography also revealed that isopropyl myristate injected subcutaneously into mice was distributed into almost all organs. (Suzuki et al. 1978 – quoted from IUCLID 2000).

41.2   Mode of action

No information has been found.

41.3   Influence on skin permeability of other chemicals

Isopropyl myristate enhanced the in vitro penetration rate of the nitrosamine N-nitrosodiethanolamine through human abdominal skin at 200 times the rate for water and 344 times the rate for propylene glycol (Bronaugh et al. 1981 – quoted from BIBRA 1988 and IUCLID 2000). It also increased the rate of benzyl alcohol penetration (Barry et al. 1985 – quoted from BIBRA 1988). Betamethasone 17-benzoate penetration of intact human forearm skin was increased by isopropyl myristate (Pepler et al. 1971 – quoted from CIR 1982). In an in vivo study, dexamethasone penetrated the stripped forearm skin (but not the intact skin) of nine humans seven times better when in gelled isopropyl myristate as compared with petrolatum (Dempski et al. 1969 – quoted from BIBRA 1988 and CIR 1982).  

The dermal absorption of ethanol and butanol through hairless mouse skin in vitro was 35 or 3 times, respectively, greater when isopropyl myristate was used as a vehicle compared to water (Garcia et al. 1980 – quoted from BIBRA 1988 and IUCLID 2000).

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