If a patient receives 650 milligrams of medication 3 1/2 hours, how many milligrams did the patient rec per hr

Question

If a patient receives 650 milligrams of medication 3 1/2 hours, how many milligrams did the patient rec per hr

Answer 1

186 mg

Answer 2

187 mg

Answer 3

Queen:

There are several answers to your question, I guess only pharmacists and doctors would even consider them:

Per hour at steady state delivery, 650mg divided by 3.5 = 185.7 mg/hr.

If this drug were given IVP (Intravenous Push), the patient received 650 mg in the first hour and the liver/kidneys would  reduce that level of active medication over time.  If IM, (IntraMuscular) then the release into the bloodstream would rise from a very low level the first hour to maximum, and then drop per hour as the "depot" became exhausted - this is dose and drug dependent, but slow release.  If trans-dermal - again, slow release into the bloodstream, it usually takes a few hours to get to the maximal absorption level, then is sustained for the period of time at the maximal dose level noted on the package....if oral, then given a normal gut, anywhere from 15 minutes to 2 hours for absorption and some slow release compounds have to be worked on by the liver to become active compounds - all this is drug and dose dependent as well.....

To figure it out per drug - since all drugs are different -  delivered differently, absorbed differently, eliminated differently - you have to know the drug, the delivery, and the patients health status (ie - surgical stress/burn stress, dehydration, etc).

I'll choose Tylenol as an example medication but without knowing what medication you were curious about or method of delivery, I will not have answered your question.

Given orally, two regular strength Tylenol will be absorbed by the gut of a healthy 20 year old (we do studies on poor students willing to act as lab rats for pay) in .5-1 hour.  So 650 mg will be absorbed into the bloodstream almost completely within one hour, a level of 600-650mg in the bloodstream in hour 1!

The half life is about 2-3 hours, so.....at 2.5 hours in this mythical healthy 20 year old....the bloodstream level should be around 300-350mg.  My math is not that exact.  If they are receiving 650mg every 4 hours, then by the time the next dose is absorbed (5 hours after the first dose if rigidly administered), they will have 600- 650 new plus a residual 150-175mg in their bloodstream at hour 5...so the second dose adds another 600-650mg to the residual level of the first dose.  That would be a total 750 to 825 mg level.  

Not to make it more confusing, up to 25% of the bloodstream dose can bind to plasma proteins making it less available for measurement or interaction....still, the patient will have received the full dose in one hour, and their levels will fall to half in about 2 hours.

If given rectally (tylenol suppositories), the characteristics are about the same - the complete dose is absorbed in one hour if administered properly; that is at the right temperature and held in the r****m for one hour.

So, the real answer to your question depends on multiple variants - if given IV, if given PO, if given PR, if given TD, intranasal or pulmonary, what drug was given, how often it is administered, etc.  If I prescribe 650mg of tylenol for a hospital patient, they will have a blood level in one hour of about 600-650 if I measure the plasma protein bound content too.  So they will have received 650mg of tylenol in that first hour.

I hope this helps....best of luck with your question, I hope the reason for your question was curiosity and not a concern for toxic overdose of something other than Tylenol.