Are there any concerns or considerations?

Limited evidence for dose-response

• No adverse effects have been reported when quinine is used in low doses (0.02 g of quinine in a 25 ml solution) prior or during exercise, and a single dose of quinine solution as described above is considered safe for use. It is unclear if concentrations higher than 2mM of quinine would trigger a higher sensory-driven response for even greater performance benefits – or, in contrast to this, induce detrimental effects.
• Currently, there is insufficient evidence to consider individual responsiveness to quinine ingestion in the sporting setting. However, ingestion of strong-tasting nutrients alongside or prior to quinine ingestion could interfere with its performance effects if it counteracts the bitter taste or sensory response triggered.

Careful handling required

• Quinine powder (Quinine Hydrochloride Dihydrate, S1125, Sigma-Aldrich Pty Ltd, Australia) is considered a hazardous chemical and requires careful handling when preparing the solution.
• Although not classed as a dangerous chemical, inappropriate handling or accidental inhaling of quinine powder can cause acute oral toxicity, impaired respiration and skin sensitisation.

Evidence for benefits still lacks certainty

Benefits might be specific to certain scenarios and short-term duration of effort. Further research is needed before more information can be provided around specific protocols, including targeted sprint events, potential uses in training and different modes of ingestion (e.g. gels or solid forms) that might be more practical to achieve in competition scenarios.