net threshold. If the patient has already reached the safety net threshold, they will be charged the normal patient contribution instead of the reduced safety net amount. Brand Premium and generic medicines In an effort to limit the cost of PBS, in July 2007 the Australian Government introduced brand premiums on medications where cheaper generic brands were available. The Brand Premium is usually the price difference between the innovator brand and the generic brand. The patient pays the Brand Premium in addition to the normal patient contribution if they decline to purchase the generic brand. The Brand Premium paid does not count toward either safety net threshold and must still be paid even after the threshold is reached. Pharmacists are allowed to substitute generic brands for prescribed brands if the brands are flagged "a" in the Schedule of Pharmaceutical Benefits, and if consent is obtained from the patient and prescriber. The prescriber's consent is always assumed to be granted unless "brand substitution not permitted" is indicated on the prescription. The National Health Act 1953 (Cth) divided the PBS formulary into an F1 category (for patented, single brand medicines) and an F2 category (for generic medicines) with reduced reference pricing between them. Academic opinion is divided about the value of these changes and the extent to which they arose from industry lobbying drawing strength from Annex 2C of the AUSFTA. Therapeutic Group Premium On 1 February 1998, another effort to limit the cost of the PBS involved the introduction of Therapeutic Group Premiums (TGPs) on medications that are priced significantly above the cheapest medication in a defined therapeutic sub-group where the drugs are considered to be of similar safety and efficacy. The TGP is the price difference between the premium brand and the benchmark (base) price for drugs in the class. The patient must pay this TGP in addition to the normal patient co-payment contribution if they have been prescribed such a medication. The TGP paid does not count toward the Safety Net threshold. However, a prescriber may obtain an exemption from the TGP if: adverse effects occurring with all of the base-priced drugs; or drug interactions occurring with all of the base-priced drugs; or drug interactions expected to occur with all of the base-priced drugs; or transfer to a base-priced drug would cause patient confusion resulting in problems with compliance. Such an exemption requires an approved PBS Authority prescription from