system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it necessary that I completely finish my antibiotics when the symptoms abate halfway through the prescription?
gpt
When symptoms go away, it is not necessarily indicative that all of the bacteria causing the infection have been killed or are once again held in check by your commensal flora. If the prescription is halted immediately after symptoms disappear, it's still possible for the infection to come back. Essentially, finishing your prescription helps to ensure that the bacteria causing the infection have been removed or are no longer out of control.

Perhaps one of the most important reasons to finish your prescription however is that it helps to prevent the development of antibiotic resistance. If you begin taking antibiotics, you are essentially culling a large number of bacteria and placing severe selection pressure on those which may be immune to the antibiotic. These are few and far between compared to the non-immune population however, and so they can be controlled by your immune system. Removing the presence of antibiotics halfway through however would allow this now antibiotic resistant-enriched population to grow back in greater numbers than before. You then risk spreading this bacteria to other people.

The same can happen with antiviral therapy. HIV-infected persons are typically placed on a cocktail consisting of three drugs to keep their viral load low. By not adhering to their prescription, or by taking it only intermittently, drug-resistant quasispecies can gain a foothold, and the drug prescription may need to be changed.