Hi,
I spent my senior year abroad in Australia myself (University of Queensland to focus on coral reef biology), and I wouldnt give up the experience for the world. Seriously, if you can get into a program it will be wonderful, it was truly one of the best years of my life. That being said you might be able to check ahead of time with your potential PharmD. schools and show them the courses at the Australian schools you are looking at. In my case I was doing it through the UC EAP program so a lot of the course had been pre-screened.
In addition Im finding as I work with my application this year and check off pre-reqs, many schools will work with you if you have all the course description and syllabi (I have narrative evaluations which helps). I didnt use my Australian courses for the science pre-reqs, but am working with some courses from ~11 years ago that have since changed numbering and names, and the admissions groups have been really helpful in figuring out which ones cover specific requirements.
If you can get into a program though, Id say go.. it also demonstrates a sense of being well-rounded as well as adventurous, and I found the UC study abroad program at least, to be quite competitive to get into which looks good.
-d