The Z-Pak contains six 250mg azithromycin tablets, and is dosed for 5 days. The directions are as follows:
- Take two tablets (500mg) by mouth on day one.
- Take one tablet (250mg) by mouth on days two through five.
It doesn't matter if you take the azithromycin tablets contained in the Z-Pak out of order as they are all the same strength, 250mg. It does matter however, that you take two tablets (500mg) as your first dose. If you don't, there is a chance that drug concentrations will not be high enough to completely cure your infection.
Day One Dose Of The Z-Pak
The day one dose of the Z-Pak (500mg) is considered a loading dose, and is used to achieve high drug concentrations in the body. The next 4 days doses, all one tablet of 250mg, are used to maintain those high drug levels.
Azithromycin is able to be dosed only once a day as it has a long half-life (around 68 hours), and one dose stays in the body for a considerable amount of time. The 500 mg day one "loading dose" produces appropriately high levels of the drug in your body, which is then maintained with the 250 mg daily doses for the next four days. If you do not take a loading dose, the concentrations of azithromycin may not reach high enough levels, which could cause your bacterial infection not to resolve.
If did not take two tablets of azithromycin as your first dose, speak with your doctor to discuss your options. If you simply took the tablets in your Z-Pak out of order but still took two tablets your first dose, it is of no consequence as they all contain 250mg.