Why are some antibiotics prescribed for 3, 5, 7, or 10 days and longer?
The frequency of antibiotic treatment (how often) is determined by how long a particular drug lasts in your system before it is metabolized or excreted. For example, Z-Pack (aka Zithromax) 5 days lasts a long time in your system, so is taken once daily, whereas Penicillin is taken 4 times daily. The duration of treatment (how many days) is determined by the location of a bacterial infection in your body. Some organs or structures are more (or less) penetrated by antibiotics, and so treatment needs to take place over a longer period of time. For example – it is harder for antibiotics to get into a sinus infection (10-14 days), easier to get to a urinary bladder infection (3-5 days). Treatment of skin infections (cellulitis) also vary with location and the type of bacteria, usually lasting 10-14 days. Most antibiotics are engineered for ease of use. Once a day is easier to take than 4 times a day, resulting in better patient compliance, and a more likely cure. While 85% of infections may
