Given most drugs can be diluted into liquids then reconstituted via some process or other your success or otherwise will probably entirely depend on whether customs inspect and test it. Have no direct experience of importing/exporting liquids, I am presuming given they are impossible (or at the very least much harder) to conceal it will literally be the luck of the draw as to how nosy Mr customs person is. Packaging it as a health supplement or medicine is unlikely to deter/fool customs, if they have made the decision to open your package they will most likely go that little step further and test, for entry into AU anyway.