To Finish Or not To Finish


I started a patient on an antibiotic 2 days ago now I don’t think that they need it. Should they just stop or finish the course to prevent resistance?



We have all seen the label put on vials reminding patients to take their antibiotic until finished; The recent WHO report on antibiotic resistance even reminds us to get patients to “complete the full prescription even when better” to prevent resistance. WHO Report
India has taken this to heart with the treatment of malaria, as a neighbourhood child is paid to visit your home to remind you to take you antimalarials in order to increase adherence rates.

There are many reasons to continue a full course but, if there is no longer a clear indication for antibiotic treatment, (i.e. pharyngitis with throat culture negative or UTI with no growth in culture) antibiotics should be stopped without fear of ‘producing resistance’.

There is no great grade 1A evidence to back this up unfortunately given the practicality of doing such a study, but many in vitro studys have shown that sub-therapeutic dosing and longer exposure to an antibiotic create pressures resulting in resistance. So by exposing an individual to more antibiotic and the possibility of a ‘7 day course’ that last 12 days (poor adherence just to finish a prescription) would exert greater pressure than a shorter exposure. I also usually remind patients if they miss a dose is it usually appropriate to catch up i.e. the important factor is the daily dose, not the number of days.

Also it is important to remember that the risks associated with antibiotics increase with a longer course.

Sir Alexandar Fleming even touched on this topic in his Nobel Lecture back in December 1945, with his foretelling closing remarks:

But I would like to sound one note of warning. Penicillin is to all intents and purposes non-poisonous so there is no need to worry about giving an overdose and poisoning the patient. There may be a danger, though, in underdosage. It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them, and the same thing has occasionally happened in the body.

The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug make them resistant. Here is a hypothetical illustration. Mr. X. has a sore throat. He buys some penicillin and gives himself, not enough to kill the streptococci but enough to educate them to resist penicillin. He then infects his wife. Mrs. X gets pneumonia and is treated with penicillin. As the streptococci are now resistant to penicillin the treatment fails. Mrs. X dies. Who is primarily responsible for Mrs. X’s death? Why Mr. X whose negligent use of penicillin changed the nature of the microbe.

Moral: If you use penicillin, use enough.

Answered by Lyle Powell.

Category: Antibiotic Therapy Principles

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