A generic drug is identical, or bioequivalent to a brand name drug in dosage form, safety, strength, route of administration, quality, performance characteristics and intended use.  Although generic drugs are chemically identical to their branded counterparts, they are typically sold at substantial discounts from the branded price.
 

How does this affect me?

When a doctor is writing a prescription, or a consumer is buying an over-the-counter medicine, they may have a choice between a branded medicine and the generic version of that medicine. Generic medicines are sometimes cheaper than brand-name medicines, but the active ingredient (the ingredient that produces the therapeutic effect of the medicine) is the same in both.

Medicines also contain inactive ingredients, which are used to formulate the active ingredient into a tablet, liquid, cream or other preparation. These inactive ingredients are called excipients, and different manufacturers do not always use the same ones when formulating their product. This is why medicines containing the same active ingredient, but made by different manufacturers, may vary in appearance. The excipients used may create small differences between them, such as in colour, or the amount of time it takes for a tablet to dissolve in the gut and be absorbed into the bloodstream, but these differences are rarely significant, which is why generic and branded medicines are (with a few exceptions) interchangeable.

All high-street pharmacists are obliged by law to dispense whatever the doctor has written on the prescription. If your doctor has prescribed a medicine by its brand name, your pharmacist must dispense that brand. However, if a medicine has been prescribed by its generic name, your pharmacist can dispense whatever version of the medicine they have available, because each version will have the same therapeutic effect. For this reason your regular medicines may vary in appearance each time you renew your prescription.

There are a few exceptions to this. There are a handful of medicines that your doctor must prescribe by the brand name. These include:

  • modified-release theophylline for asthma, eg Nuelin SA, Slo-phyllin, Uniphyllin continus

  • modified-release aminophylline for asthma, eg Norphyllin SR, Phyllocontin continus

  • modified-release diltiazem for angina and high blood pressure, eg Adizem-XL, Slozem, Tildiem retard

  • modified-release nifedipine for angina and high blood pressure, eg Adalat retard, Slofedipine XL

  • the immunosuppressant ciclosporin, eg Neoral

  • lithium, which is a mood stabiliser for manic depression, eg Camcolit, Liskonum, Priadel

  • fentanyl patches, eg Durogesic DTrans

  • carbamazepine, phenytoin and sodium valproate for epilepsy.

If you take any of the above medicines it is important that you always take the same brand, because different brands of these medicines may differ significantly in the way they are absorbed. If a different brand than usual is taken, the blood levels of the active ingredient could stray outside the required therapeutic range. If the amount in the blood becomes too low, the effect of the medicine may be lost; if the amount in the blood becomes too high, there may an increased chance of side effects.

Your pharmacist will make sure you receive the correct medicine, but if you are taking any of the above medicines it is also wise for you to know which brand you normally take. If you are ever concerned that the medicine you have been given is different to what you normally take, always check with your pharmacist, who will be happy to explain any discrepancies.