Timing of Medication Dose Responses

Question 1

Minimum effective concentration (MEC)

Answer 1

The minimum effective concentration (MEC) is the plasma level of a
medication below which the effect of the medication does not occur.The
toxic concentration is the level at which toxic effects occur. When a
medication is prescribed, the goal is to achieve a constant blood level
within a safe therapeutic range, which falls between the MEC and the
toxic concentration. When a medication is administered
repeatedly, its serum level fluctuates between doses. highest level is peak concentration and lowest level is trough concentration. With IV infusions the peak concentration
occurs quickly, but the serum level also begins to fall immediately. Some
medication doses (e.g., vancomycin) are based on peak and trough serum
levels. The trough level is generally drawn 30 minutes before
administering the medication, and the peak level is drawn whenever the
medication is expected to reach its peak concentration.

Question 2

Know the following time intervals of medication action to

anticipate the effect of a medication:

Answer 2

1. Onset of medication action: Period of time it takes after you administer a medication for it to produce a therapeutic effect
2. Peak action: Time it takes for a medication to reach its highest effective peak concentration
3. Trough: Minimum blood serum concentration of medication reached just before the next scheduled dose
4. Duration of action: Length of time during which a medication is present in a concentration great enough to produce a therapeutic effect
5. Plateau: Blood serum concentration reached and maintained after repeated, fixed doses

Question 3

Biological half-life

Answer 3

time it takes for excretion processes to lower the serum medication concentration by half. To maintain a therapeutic plateau, a patient needs to receive regular fixed doses. After an initial medication dose, the patient receives each successive dose when the previous dose reaches its half-life.

Question 4

Time-critical medications

Answer 4

administer time-critical medications at a precise
time, within 30 minutes before or after their scheduled time. You administer non–time-critical medications within 1 to 2 hours of their scheduled time

Question 5

Common Dosage Administration Schedules

Answer 5

Dosage Schedule (Meaning) | Abbreviation
Before meals | AC, ac
As desired | ad lib
Twice each day | BID, bid
After meals | PC, pc
Whenever there is a need | prn
Every morning, every AM  | q am
Every hour | qh
Every day | Daily
Every 4 hours | q4h
4 times per day | QID, qid
Give immediately | STAT, stat
3 times per day | TID, tid

Question 6

Terms Associated with Medication Actions

Answer 6

Onset Time - it takes after a medication is administered for it to produce a response
Peak Time - it takes for a medication to reach its highest effective concentration
Trough - Minimum blood serum concentration of medication reached just before the next scheduled
dose
Duration - Time during which medication is present in concentration great enough to produce a
response
Plateau - Blood serum concentration of medication reached and maintained after repeated fixed doses