Generic vs Brand Prescription Medicines in Australia

This guide explains the rules, not what to take. Substitution decisions belong with you, your prescriber, and your pharmacist.

Generic medicines defined

A generic prescription medicine is one that copies the formulation of an original brand once the patent expires. It contains the same active ingredient, at the same dose, in the same dose form (tablet, capsule, cream, inhaler), released over a bioequivalent time window in the body.

The packaging, the tablet colour, the inactive ingredients (fillers, binders, dyes), and the brand name can all differ. The therapeutic substance and the dose do not.

Generic does not mean lower quality. Every generic registered for supply in Australia must meet the same TGA quality, safety and efficacy requirements as the original brand, though the evidentiary pathway a generic sponsor follows to demonstrate this differs from the original brand's full registration pathway. The TGA inspects generic manufacturers on the same Good Manufacturing Practice (GMP) basis as innovator brands.

TGA bioequivalence requirements

Before a generic can be supplied in Australia, the sponsor must demonstrate bioequivalence to the original brand. Bioequivalence is a statistical comparison of specific pharmacokinetic measures, principally peak concentration and total exposure, not a claim that a tablet contains 80 to 125 per cent of the labelled active ingredient. Under TGA guidelines, those measures must sit within 80 to 125 per cent of the original brand's own measures, with 90 per cent confidence.

The TGA publishes its approach to bioequivalence at tga.gov.au.

A small number of medicine classes are flagged for extra caution on substitution because the difference between an effective dose and a problematic dose is narrow. These are called narrow therapeutic index medicines. For those, your prescriber may write "brand name only, do not substitute" on the script, and the pharmacist will dispense exactly that. The TGA and the Pharmacy Board both recognise this as a legitimate clinical decision; your prescriber and pharmacist can tell you if a medicine you take falls into this category.

Why generics cost less

The original brand carries the cost of developing the medicine: the research, the clinical trials, the regulatory approvals, the marketing. While the patent is in force, the original manufacturer is the only legal supplier and can set a price that recovers those costs.

Once the patent expires, other manufacturers can apply for TGA approval to supply the same active ingredient. They did not pay for the original research, so they can sell at a lower price. With multiple suppliers competing, the price falls further.

The PBS uses this competition to drive the subsidised price down. Through price disclosure, PBS prices for off-patent medicines are revised every six months based on what the market actually charges. Over time, the PBS price drops below the standard general co-payment of $25, at which point the medicine becomes a below co-payment medicine and you pay the actual price, not the full $25.

The brand premium (the un-subsidised gap)

When a generic is available at the lower PBS price and you choose to stay on the original brand, the difference between the two is called the brand premium. The PBS subsidises the cost up to the generic price. Anything above that, you pay out of pocket.

A few specifics:

• The brand premium can be anywhere from a couple of dollars to $20 or more per script, depending on the medicine.
• The brand premium does not count toward your PBS Safety Net threshold. Once you cross the threshold, you still pay the brand premium on top of the reduced or free co-payment.
• The original manufacturer sets the brand premium. Different pharmacies may charge the same premium on the same script, since it is set by the manufacturer rather than the pharmacy.

If cost matters to you, ask the pharmacist what the brand premium is before they dispense. They will tell you the dollar figure and offer the generic at the standard co-payment.

When you might still choose the brand

There are legitimate reasons to stay on the original brand. None of them are about quality. All of them are individual, and a pharmacist or prescriber is the right person to talk through which applies to you.

• Your prescriber has marked the script "brand name only". This is a clinical decision and the pharmacist will follow it, most often for a narrow therapeutic index medicine.
• You have a confirmed allergy or intolerance to an excipient in the generic. The active ingredient is the same; the inactive ingredients (lactose, gluten, certain dyes) can differ. If you react to a filler, that is a real medical reason to stay on a specific formulation.
• Continuity matters for a stable condition. If a chronic condition has been stable for years on one specific brand, your prescriber may decide that the predictability is worth the brand premium. That is a conversation between you, the prescriber, and the pharmacist.
• You find a particular dose form easier to use. Some patients find one tablet easier to swallow, one inhaler easier to actuate, or one packaging format easier to track. If that supports adherence, it matters.

Outside those reasons, the TGA position is that an approved generic and the original brand are clinically interchangeable.

How to ask your pharmacist about substitution

Pharmacists are trained to discuss substitution at the counter. You can ask plainly:

• "Is there a generic for this script?"
• "What is the price difference between the brand and the generic?"
• "Are there any reasons I should stay on the brand for this specific medicine?"
• "Has my prescriber marked the script 'do not substitute'?"

The pharmacist can show you both options on the dispensing screen, explain any brand premium, and dispense whichever you choose, unless the prescriber has marked the script "brand name only".

If you switch from a brand to a generic and notice anything unusual in the days that follow, different effect, different side effects, anything that does not match your usual experience, tell the prescriber and the pharmacist. The TGA's Adverse Event reporting line accepts reports from patients and from clinicians.