The Australian Injectable Drug Handbook can be referenced in the same way as other health databases such as the Australian Medicines Handbook or AusDI.
There is a page in the APA referencing guide that gives examples (look for the' Specialist subject material' heading and click on the Health databases tab) - https://library.nd.edu.au/instruction/referencing/apa/other
For in-text citations, it will follow the format of ("name of drug", copyright date in database) e.g. ("Benzathine Penicillin", 2020)
For the reference list, use the following format:
Name of drug. (date). In Australian injectable drug handbook. Retrieved from https://www.aidh.hcn.com.au
e.g. Benzathine Penicillin. (2020). In Australian injectable drug handbook. Retrieved from https://www.aidh.hcn.com.au