Although an antibiotic's half-life equals half the time it takes to leave an individual's system, it takes five half-lives for the drug to clear a person's system completely, according to HealthTap. Each drug has its own specific half-life, so different antibiotics remain in the system for different lengths of time.
If an antibiotic has a half-life of one hour, it is safe to assume that the medication has left an individual's body after five hours. However, half-lives vary significantly from one antibiotic to another, so patients should consult their physicians or pharmacists for the precise half-lives of the specific antibiotics they've been prescribed.
