I am "re-posting"  a reply I wrote to AtLast's blog regarding missing doses of our HAART drug combination therapy. Well admitedly I'm not a pharmacist or doctor; but I will share what I do know and most Infectious Disease Doctors won't tell you……..I have several friends that are pharmacists and also some pharmaceutical reps – that passed on this bit of information to me…. Every pill you take has what is known as a "half life" (Pharmacological definition – The period of time over which the concentration of a specified chemical or drug takes to fall to half its original concentration in the specified fluid or blood) The Half life of any pill is usually the minimum acceptable level of medicine needed in the blood stream to still effectively do its  prescribed job. In our case on pills like Atripla and Sustiva and other HIV meds that are taken daily,… the half life of the pill is actually 36 hours minimum or more; and does vary according to each pill and I have not accounted for how long it takes to digest it. They make us take it daily so that our minimum amount of medicine in our bloodstream never drops below the "half -life" level….AND so that the HIV does NOT become resistant to the Medicine. I am in no way advocating anyone trying to self administer meds or change how they take them! However, if you miss a dose for a daily med and its less than 12 hours from when you were supposed to take it – don't flip out. Just take it and then go back to your normal schedule. The same math applies to 12hour pills having an 18 hour "half life (2X a day) etc. If it was me, ask your pharmacist what the "half -life" is for all of your meds so that you know this in the future.  – B