Actually it is right to the point.
Are you talking about a Minimum Inhibitory Concentration Plate, where you look at the sensitivity of organisms to an antibiotic?
First problem is that in vitro does not correspond to in vivo; an agar plate cannot be hurt by an antibiotic, whereas the individual can be.
Antibiotics can cause serious side effects, such as renal damage, hearing loss, granulocytosis, death.
But my point was made, you can't just say"well can you take a bunch of aspirin? No!"
In the case of cortisone the doses are different based on the manner of administration, i.e. injection or enteral, the former allowing for prolonged pharmacokinetics and the latter of shorter duration.
There are oral penicillins, which must be taken in multiple daily doses and then there are injectable penicillin preparations, which only require one initial dose, since the drug is slowly hydrolyzed and released from its depot.