A new evaluation method for +Gz tolerance with loratadine by using a near-infrared spectroscopy.
Aeromedical Laboratory, Japan Air Self-Defense Force, Tachikawa, Tokyo, Japan. ymiyamo@rivo.mediatti.net.
ABSTRACT: BACKGROUND: Loratadine (Claritin(R)), an over the counter antihistamine in U.S. and UK, is acceptable for use without adverse side effects by aircrew with mild or moderate allergic or other situations requiring an antihistamine. Although +Gz (head to foot direction) tolerance testing for aircrew with loratadine has not been documented in the published literature, it is commonly accepted that loratadine dose not effect +Gz tolerance. The purpose of this study was to offer and validate a new evaluation method for +Gz tolerance testing with loratadine by using a near-infrared spectroscopy (NIRS). METHODS: A double-blind, placebo-controlled, randomized, crossover protocol was used to administer 10 mg of loratadine or placebo in nine healthy subjects. The subjects didn't wear anti-G suit. The +Gz exposure profiles consisted of, in series, a gradual onset ran (0.1 G.sec-1) to the subject's visual end-point (peripheral light loss) or loss of consciousness (GLOC), and rapid onset run (1.0 G.sec-1) to the subject's same end-point. In this study, G-level tolerance was defined as the +Gz level at visual end-point and/or at GLOC. As a subject's G-duration tolerance, we measured the total time (seconds) during rapid onset run. Otherwise, to confirm the effect of loratadine on +Gz tolerance, we measured the cerebral NIRS variables (hemoglobin concentration changes and tissue oxygenation index) as a new quantitative method for +Gz tolerance during a centrifuge experiments. RESULTS: No significant differences were observed in +Gz tolerance (+Gz level, duration time and NIRS variables) between subjects taking loratadine and placebo. CONCLUSION: Our results demonstrate that loratadine has no detectable effect on +Gz tolerance by using a new method with cerebral NIRS variables and the traditional method with +Gz level and duration time. This study represents the first use of a quantitative parameter such as cerebral NIRS variables to assess the effects of a drug on acceleration tolerance.
PMID: 18226263 [PubMed - in process]
PMCID: PMC2265702