Pyridostigmine, diethyltoluamide, permethrin, and stress: a double-blind, randomized, placebo-controlled trial to assess safety

A systematic review of performance-enhancing pharmacologicals and biotechnologies in the Army

INTRODUCTION

In 2015, the Australian Army commissioned a systematic review to assess the evidence on effectiveness and safety of pharmacological and biotechnological products for cognitive enhancement specifically in Army personnel.

METHODS

Searches for studies examining biotechnological and pharmacological products in Army populations were conducted in December 2015. Cochrane CENTRAL, MEDLINE, EMBASE, CINAHL and PsycINFO were searched without date or language restrictions. WHO's International Clinical Trials Registry Platform and ClinicalTrials.gov were searched to identify ongoing trials. Studies meeting inclusion criteria were evaluated for risk of bias using Cochrane's Risk of Bias tool. Due to heterogeneity of findings, meta-analysis could not be conducted. Findings were synthesised narratively and by vote-counting method.

RESULTS

Sixteen pharmacological enhancement products were evaluated in 22 randomised controlled trials (RCTs), involving 1284 personnel. Only three of the studies were published since 2010. The interventions evaluated were varied, including supplements (eg, carbohydrate), stimulants (eg, caffeine) and hormones (eg, melatonin). Generally, caffeine provided an improvement in performance compared with placebo on 5/7 reported cognitive outcomes, followed by levothyroxine (four cognitive outcomes) and prazosin (three cognitive outcomes). Performance results were mixed (finding an improvement and no effect in comparison to placebo) for caffeine and melatonin on two outcomes. No evidence was found pertaining to biotechnological products. Studies rarely reported safety outcomes (eg, adverse events and addiction).

CONCLUSION

Findings from this review need to be interpreted with considerable caution. Future studies should include outcomes such as acute and long-term adverse events, and should evaluate cognitive performance using cognitive tests that are specific to the Army population.

In vitro kinetic interactions of DEET, pyridostigmine and organophosphorus pesticides with human cholinesterases

The simultaneous use of the repellent DEET, pyridostigmine, and organophosphorus pesticides has been assumed as a potential cause for the Gulf War Illness and combinations have been tested in different animal models. However, human in vitro data on interactions of DEET with other compounds are scarce and provoked the present in vitro study scrutinizing the interactions of DEET, pyridostigmine and pesticides with human acetylcholinesterase (hAChE) and butyrylcholinesterase (hBChE). DEET showed to be a weak and reversible inhibitor of hAChE and hBChE. The IC(50) of DEET was calculated to be 21.7mM DEET for hAChE and 3.2mM DEET for hBChE. The determination of the inhibition kinetics of pyridostigmine, malaoxon and chlorpyrifos oxon with hAChE in the presence of 5mM DEET resulted in a moderate reduction of the inhibition rate constant k(i). The decarbamoylation velocity of pyridostigmine-inhibited hAChE was not affected by DEET. In conclusion, the in vitro investigation of interactions between human cholinesterases, DEET, pyridostigmine, malaoxon and chlorpyrifos oxon showed a weak inhibition of hAChE and hBChE by DEET. The inhibitory potency of the tested cholinesterase inhibitors was not enhanced by DEET and it did not affect the regeneration velocity of pyridostigmine-inhibited AChE. Hence, this in vitro study does not give any evidence of a synergistic effect of the tested compounds on human cholinesterases.