A patient is receiving vancomycin IV every 8 hours at 0800,1600,and 2400.A serum peak and trough level is ordered after the third dose,which will be given at 1600.When should the nurse order the trough level?

A) 1630
B) 1800
C) 2330
D) 2400

The point at which the lowest amount of drug is in the serum is the trough concentration.Some medication doses (e.g. ,vancomycin and gentamicin)are based on peak and trough serum levels.A patient's trough level is drawn as a blood sample 30 minutes before the drug is administered,and the peak level is drawn whenever the drug is expected to reach its peak concentration.The third dose will be given at 1600,which means that the lowest level of drug will be present 30 minutes before the fourth dose at midnight.A patient's trough level is drawn as a blood sample 30 minutes before the drug is administered.1630 is 30 minutes after the drug is administered.1800 is 2 hours after the drug is administered.If the medication reaches its peak concentration in 2 hours,this could be a peak concentration,because the peak level is drawn whenever the drug is expected to reach its peak concentration.2400 is the time that the next dose is due.A patient's trough level is drawn as a blood sample 30 minutes before the drug is administered.