Meds and you

16 November 2009

When not to substitute

The Medicines Control Council recommends that substitution with generics should not occur in certain cases.

The Medicines Control Council (MCC) recommends that substitution should not occur when prescribing and dispensing medicines which:

a) Have a narrow therapeutic range;
b) Have been known to show erratic intra- and inter-patient responses;
c) Are contained in dosage forms that are likely to give rise to a clinically significant bioavailability problem, e.g. extended or delayed release preparations, as well as those known to be super bioavailable*;
d) Are intended for the critically ill and/or geriatric and paediatric patients.

In terms of the above-mentioned factors, the following medicines have, on occasion, been known to present bioequivalence problems and should ideally not be interchanged with a generic:

  • Alendronate tablets or capsules
  • Atenolol tablets or capules
  • Carbamazepine tablets
  • Chlorpromazine tablets
  • Dexamethasone tablets
  • Diethystilboestrol tablets
  • Digoxin tablets
  • Disulfiram tablets
  • Ethinyl Oestradiol tablets
  • Fluoxymesterone tablets
  • Furosemide tablets
  • Glibenclamide tablets
  • Hydralazine, hydrochlorothiazide and Reserpine combination tablets
  • Hydralazine & Hydrochlorothiazide combination tablets
  • Hydrocortisone tablets
  • Hydrocortisone Acetate injection
  • Isoproterenol Metered dose inhaler
  • Isoethrane Metered dose inhaler
  • Isorbide Dinitrate sustained release tablets and capsules
  • Itraconazole tablets or capsules
  • Levodopa Capsules and tablets
  • Nfedipine: all extended/delayed release formulations
  • Oestrogens, Conjugated tablets
  • Oestrogens Esterifies tablets
  • Penicillin G Benzathine injections
  • Phenytoin tablets and capsules
  • Phytomenadion injection
  • Prazosin Hydrochloride tablets 5mg*
  • Prednisolone tablets
  • Prednisolone Acetate injections
  • Prednisolone Tebutate injection
  • Prednisone tablets
  • Promethazine tablets
  • Propylthiouracil tablets
  • Reserpine tablets
  • Reserpine and Chlorothiazide combination tablets
  • Reserpine & Trichloromethiazide combination tablets
  • Tamoxifen tablets or capsules
  • Theophylline controlled release tablets/capsules
  • Triamcinolone tablets
  • Trichloromethiazide tablets
  • Warfarin Sodium tablets

Non-inclusion of any particular medicine does not necessarily mean it is substitutable. The list is periodically reviewed, and alterations are made at the discretion and recommendation of the MCC.


  • United States Food and Drug Administration. Generic drugs: what you need to know. [online] 2002 [cited 2007 Jul 09]. Available at:
  • United States Food and Drug Administration. Savings from generic drugs purchased at retail pharmacies. [online] 2004 [cited 2007 Jul 09]. Available at
  • United States Food and Drug Adminstration: Office of Generic Drugs. [online] 2007 [cited 2007 Jul 09]. Available at:
  • SA Medicines Control Council. Guidelines on generic substitution. Government Gazette 2003;25145:183-5.


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