Use of amoxycillin trihydrate/potassium clavulanate

Editor, – In his article 'The promotion of Augmentin' (Aust Prescr 1993;16:89), Dr P. Mansfield ranks several antibiotics for the treatment of otitis media. This ranking is in accordance with recommendations made by the Victorian Drug Usage Advisory Committee.¹ Dr Mansfield seems to justify the ranking by citing Appelman et al.² in stating that Augmentin 'has no significant benefit over placebo in treating children over two years with acute otitis media'. The obvious inference we are meant to draw is that Augmentin is relatively ineffective and thus we ought not to expose our patients to the risk of drug-induced morbidity by using it. Thus, the first choice of the several antibiotics listed is amoxycillin, with Augmentin being placed last.

But is not the effective principle in both preparations the same? As I understand it, potassium clavulanate has no deleterious effect on the actual bactericidal efficacy of amoxycillin. Thus, is it not the case that amoxycillin, on its own, ought also to have 'no significant benefit over placebo'? How then can it be ranked first over the other antibiotics listed, while, when compounded with something to improve it, it ranks last? Is Dr Mansfield being just as 'inappropriate' as he claims the pharmaceutical manufacturers are in their advertising?

I agree that as far as morbidity is concerned, there may be good cause to prefer one preparation over the other, but I think that the argument as stated does not follow the laws of logic. Or is there some reason why the amoxycillin trihydrate in Alphamox, Amoxil, Cilamox, Fisamox or Moxacin has better bactericidal properties than the amoxycillin trihydrate in Augmentin?

Perhaps he can enlighten us?

A.G. Moskwa
Senior Lecturer
School of Pharmacy and Medical Sciences
University of South Australia
Adelaide, S.A.

Dr P. Mansfield, the author of the article, and Dr M.L. Mashford, Chairman of the Antibiotic Guidelines Subcommittee of the Victorian Drug Usage Advisory Committee, comment:

The aim of MaLAM's reports for Australian Prescriber is to hint at the reasons for asking questions about drug promotion such as SmithKline Beecham's claim that 'When you need to be sure in otitis media and sinusitis, you need Augmentin'. That promise of certainty is seductive, but real life is complex and uncertain.

Augmentin is more effective than amoxycillin alone against beta-lactamase producing bacteria in vitro. However, our responsibility is to treat people, not Petri dishes. In otitis media and sinusitis, in vitro susceptibility does not predict clinical outcome.^3,4 Around 76% of patients with otitis media will recover without an antimicrobial.³ In some of the remaining 24%, viral involvement will defeat any antimicrobial.¹

The Victorian Drug Usage Advisory Committee's new 1994-95 edition of 'Antibiotic Guidelines' still recommends amoxycillin for otitis media, but only when severe signs are present. A New South Wales Health Department Working Party has also recommended that amoxycillin be used.⁵ Perhaps the best evidence to support those recommendations is a British study which found that amoxycillin is better than placebo in the short term, but not in the medium or long term.⁶

Future clinical studies may enable us to identify which patients are most likely to benefit from antimicrobials rather than suffer adverse effects. Meanwhile, we can not 'be sure' whom to treat with what. However, it is logical to prefer amoxycillin. Augmentin is more expensive and is associated with a 13% incidence of adverse effects.⁷ Because adverse effects cause more patients to prematurely cease courses of Augmentin⁸, it may be even less effective than amoxycillin.