Sir, more than 40 years ago I attended a memorable lecture delivered by Dr James Murdoch of Edinburgh, one of the original members of the 'Dunlop Committee' which, I understand, is the forebear of today's NICE. I recollect that he advised the delegates that while about 15% of antibiotics prescribed could be shown to be beneficial, about 5% were potentially dangerous and that the other 80% were neither beneficial nor harmful to the individual but potentially harmful as their prescription could lead to the development of sensitivity and resistance.

It was, therefore, somewhat distressing to read the well informed paper by Professor Michael Lewis (BDJ 2008; 205: 537), a highly regarded clinician, warning that we appear to have learned nothing since then and that, by inference, previously fairly innocuous infections could now become life threatening. Everyone, patient and clinician alike, should be grateful to him. Hopefully some attention will now be paid to such cautionary words. I worry that otherwise the value of these wonderful drugs may be rendered useless less than a century after penicillin's discovery.

In the middle 1950s undergraduate medical and dental students were warned of the dangers of prescribing inadequate doses of antibiotics and of the necessity for patients to complete any prescribed course if the development of both resistance and sensitivity in the community was to be prevented. I wonder, after reading the letter from Dr P. R. Williams (BDJ 2008; 205: 525), if there has been a change of thinking about this advice, if previously unacceptable dosages are now considered to be adequate and without risk. Incidentally, I and my contemporaries were taught at all stages of our education also to warn every patient of the dangers of consuming alcohol after any dental extraction, especially the probability of unwanted, worrying bleeding, no matter which day of the week it was.