- R E Ferner, consultant clinical pharmacologist12,
- Warren Lenney, consultant respiratory paediatrician3,
- John F Marriott, professor of clinical pharmacy4
- 1West Midlands Centre for Adverse Drug Reactions, City Hospital, Birmingham B18 7QH
- 2School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT
- 3Academic Department of Child Health, University Hospital of North Staffordshire and Keele University, Stoke-on-Trent, Staffordshire ST4 6QG
- 4School of Life and Health Sciences, Aston University, Birmingham B4 7ET
- Correspondence to: R E Ferner
- Accepted 13 April 2010
Consultation on the Department of Health’s decision to introduce generic substitution into English primary care completed at the end of March.1 The proposal, which is part of the 2009 pharmaceutical price regulation scheme for the whole of the United Kingdom, would allow pharmacists and other dispensers to fulfil a prescription for branded medicines by dispensing an equivalent generic medicine.2 Doctors will be able to over-ride substitution, and the department proposes producing a list of those drugs that can be substituted.
Generic substitution is already the norm in NHS hospitals, and 83% of NHS general practice prescribing in 2008 was for generic medicines. It is also used in Australia, the United States, and many countries in the European Union.3 4 Nevertheless, the UK proposal has been vociferously opposed by patient groups, doctors, and drug companies, sometimes in concert.5 Here we discuss some of the issues that make generic substitution in the community contentious.
Differences in content
Many generic drugs contain exactly the same active ingredient as the originator product. However, sometimes it is in a different chemical form, such as another salt. Erythromycin, for example, is available as ethyl succinate, lactobionate, stearate, and erythromycin base. The actions of different forms may not be identical, and they may have different solubilities and absorption characteristics. Dosages expressed as the weight of a salt rather than the weight of the active moiety (chemical entity) will also differ—for example, 200 mg ferrous sulphate contains as much elemental iron (65 mg) as 557 mg of ferrous gluconate. However, if the concentration at the site of action and rate of absorption of branded …