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.

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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.

References:

  • United States Food and Drug Administration. Generic drugs: what you need to know. [online] 2002 [cited 2007 Jul 09]. Available at: http://www.fda.gov/fdac/features/2002/502_generic.html
  • United States Food and Drug Administration. Savings from generic drugs purchased at retail pharmacies. [online] 2004 [cited 2007 Jul 09]. Available at http://www.fda.gov/cder/consumerinfo/savingsfromgenericdrugs.htm
  • United States Food and Drug Adminstration: Office of Generic Drugs. [online] 2007 [cited 2007 Jul 09]. Available at: http://www.fda.gov/cder/ogd/
  • SA Medicines Control Council. Guidelines on generic substitution. Government Gazette 2003;25145:183-5.

 

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