It might not be a good idea to import a drug to Australia without prescription, from the stories I have heard about Australian customs.
If its personsl use and not selling it the worst that will happen is they confiscate your order and send you a letter saying its naughty. Ive had a couple of these letters after ordering supplements from iherb i didnt know were restricted here in Australia . One was melatonin but the law has changed since than.
Antibiotics, antivirals and a few other basic meds have never been a problem, even after being opened by customs. The importation laws on prescription medication is no more than a 3 month supply for personal use or a relative, and is not a restricted drug such as narcotics etc. The rest of the law is open to different interpretation. But i think the customs officials have bigger fish to fry then someone who has ordered 90 valtrex tabs to be honest. More than likely feel sorry for you because they think u have genital herpes u cant get treated for.
Its a different story if you try to bring in large quantities to sell.
Thats my experience anyway.