STAY­ING THE AN­TIBI­OTIC COURSE

Fears about an­tibi­otic re­sis­tance have opened up a can of germs. For sev­eral con­di­tions the needed an­tibi­otic treat­ment du­ra­tion is ac­tu­ally shorter than what we once thought.

Cosmos - - View Point - NOR­MAN SWAN is a doc­tor and multi-award win­ning pro­ducer and broad­caster on health is­sues.

WE’RE FRE­QUENTLY CON­FRONTED

with doom and gloom sto­ries about the an­tibi­otic cri­sis. As an­timi­cro­bial re­sis­tance grows, and the pipe­line of new an­tibi­otics shrinks, there may soon be noth­ing left on phar­ma­cists’ shelves to treat some in­fec­tions.

Overuse of an­tibi­otics is to blame. A re­port pub­lished in 2016 by the Aus­tralian Com­mis­sion on Safety and Qual­ity in Health Care claimed Australia has among the world’s high­est an­tibi­otic pre­scrib­ing rates along with very high rates of com­mu­nity re­sis­tance to van­comycin, one of the last lines of an­tibi­otic de­fence. So some­thing needs to be done. There’s the tra­di­tional ad­vice. Doc­tors need to de­sist from pre­scrib­ing an­tibi­otics for vi­ral in­fec­tions (they don’t work) and re­strict pre­scrip­tions to clear bac­te­rial in­fec­tions. They should pre­scribe the old­est, cheap­est an­tibi­otics, which are ac­tu­ally still ef­fec­tive for most in­fec­tions. Given re­sis­tance in­evitably emerges a few years af­ter a new an­tibi­otic is in­tro­duced, the lat­est weapons in the arsenal, like van­comycin, need to be held in re­serve for as long as pos­si­ble.

But now there’s a new piece of ad­vice – and it’s con­tentious. In the July 2017 edi­tion of the Bri­tish Med­i­cal Jour­nal, some ex­perts ar­gued that pa­tients should stop fol­low­ing the time-honoured in­struc­tion to “com­plete the course” of pre­scribed an­tibi­otics.

The idea you should chuck the an­tibi­otics once you’re feel­ing bet­ter, though, has riled other ex­perts who say there is still good rea­son to fol­low the tra­di­tional ad­vice.

The orig­i­nal idea of stay­ing the course on an­tibi­otics, para­dox­i­cally, was to pre­vent re­sis­tance by killing off ev­ery last of­fend­ing germ. Ac­cord­ing to this view, the germs that took the long­est to die were likely to be the most re­sis­tant.

The pro­po­nents of “not fin­ish­ing the course” say it is the ex­act op­po­site. There is lit­tle ev­i­dence that the longer you stay on the course the more likely you are to kill off all the germs. In­stead, it is the pro­longed ex­po­sure to an­tibi­otics that fos­ters the evo­lu­tion of re­sis­tance in the mi­cro­bial com­mu­ni­ties we host. As sen­si­tive bac­te­ria are quickly killed off, it is the mi­crobes with in­her­ent re­sis­tance that gain the ad­van­tage and mul­ti­ply. So stop­ping early is good, pro­po­nents say, be­cause it re­moves the evo­lu­tion­ary pres­sure on the mi­cro­bial com­mu­ni­ties.

The tra­di­tion­al­ists say that only tak­ing an­tibi­otics till you feel bet­ter is sim­plis­tic and risky for a va­ri­ety of rea­sons. For one thing, for some con­di­tions there is ev­i­dence the bugs can bounce back if the course of treat­ment is too short. Tu­ber­cu­lo­sis, for ex­am­ple, needs months of treat­ment. The same may be true for Sta­phy­locuc­cus au­reus (golden staph). For an­other, a blan­ket rec­om­men­da­tion to stop tak­ing an­tibi­otics ear­lier doesn’t take ac­count of vari­a­tions in the ef­fec­tive­ness of dif­fer­ent an­tibi­otics that work in dif­fer­ent ways over var­i­ous time spans.

As is of­ten the case in medicine, de­bates like this leave you and me con­fused about the right thing to do. The trou­ble is there is not enough data to en­lighten us. There is, though, some ev­i­dence that can be brought to bear.

It turns out that for sev­eral con­di­tions the nec­es­sary treat­ment du­ra­tion is ac­tu­ally shorter than what we once thought. For in­stance, while the vast ma­jor­ity of sore throats are vi­ral and there­fore not helped by an­tibi­otics, a small pro­por­tion are caused by bac­te­ria such as strep­to­cocci (strep). When I was a med­i­cal stu­dent we were taught you needed at least 10 days of peni­cillin to treat a strep throat. Now the ev­i­dence with newer an­tibi­otics is that three to six days are enough in other­wise healthy kids.

An­other ex­am­ple is a lower uri­nary (blad­der) in­fec­tion. A re­view of the ev­i­dence sug­gests three to six days are as ef­fec­tive as longer cour­ses. In chil­dren it is even shorter – two to four days.

Ex­per­i­ments in piglets have found that such a re­duc­tion in an­tibi­otic du­ra­tion could re­duce the ex­cre­tion of re­sis­tant germs in fae­ces by 75%.

With oti­tis me­dia (mid­dle ear in­fec­tion) there is ques­tion­able ev­i­dence that the rou­tine use of an­tibi­otics is ben­e­fi­cial at all.

On the other side, the ev­i­dence sug­gests that the ul­cer germ Heli­cobac­ter py­lori (which in­creases the risk of stom­ach cancer) re­quires 14 days of an­tibi­otic ther­apy to be elim­i­nated. So rather than blan­ket pro­nounce­ments on fin­ish­ing or not fin­ish­ing a course, doc­tors and pa­tients need bet­ter ev­i­dence and con­fi­dence as to what length of course is ac­tu­ally ef­fec­tive for a par­tic­u­lar ill­ness.

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