Pharmacokinetics &
Routes of Administration &
Pharmacodynamics (Pt. 1)
Pharmacokinetics - CORRECT ANSWER-refers to how medications travel through the body.
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B -How the BODY acts on the DRUG
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Pharmacokinetics in Clinical Practice - CORRECT ANSWER-i. onset of drug action (how long it will
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take to see beginning of therapeutic effects)
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ii. drug half-life
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iii. timing of the peak effect (how long it will take to see the maximum effect of the drug)
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iv. duration of drug effects (how long the pt will experience the drugs effect)
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v. metabolism (biotransformation) of the drug
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vi. site of excretion
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,Critical Concentration - CORRECT ANSWER-Critical Concentration: the amount of a drug needed
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to cause a therapeutic effect.
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B -after a drug is administered, its molecules first must be absorbed into the body, then make their
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B way to *reactive tissues.* If a drug is going to work properly on these reactive tissues, and
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B thereby produce therapeutic effects, it must attain a *sufficiently high concentration in the
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B body.*
Loading Dose - CORRECT ANSWER-Loading Dose: a higher dose than that usually used for
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treatment to reach the critical concentration.
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B -the critical concentration is then maintained by using the *recommended dosing schedule*
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Some drugs may take a prolonged period to reach a critical concentration. If their effects are
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needed *QUICKLY,* a loading dose is recommended.
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Examples: B
1. Digoxin (Lanoxin): drug used to increase the strength of heart contractions
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2. Many of the Xanthine Bronchodilators (e.g. aminophylline/theophylline) used to treat asthma
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attacks are often started by a loading dose.
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Dynamic Equilibrium - CORRECT ANSWER-The *actual concentration that a drug reaches in the
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body* results from dynamic equilibrium involving several processes/phases:
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B i. Absorption from site of entry
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B ii. Distribution to the active site
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, B iii. Metabolism (biotransformation) in the LIVER
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B iv. Excretion from the body
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These processes are key elements in determining the *amount of drug (dose)* and the
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*frequency of dose repetition (scheduling)* required to achieve the *critical concentration for
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the desired length of time.*
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Phase: Absorption (ATI) - CORRECT ANSWER-The transmission of medication from the location of
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administration [GI tract, muscle, skin, mucous membrane, or subcutaneous tissue] to the
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bloodstream.
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i. The *RATE* of medication absorption determines how soon the medication will take effect
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ii. The *AMOUNT* of medication the body absorbs determines the intensity of its effects
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iii. The *ROUTE* of administration affects the rate and amount of absorption
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Phase: Absorption (textbook) - CORRECT ANSWER-To reach reactive tissues, a drug must first
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make its way into the *circulating fluids* of the body.
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*Absorption* refers to what happens to a drug from the time it is *introduced to the body until it
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reaches the circulating fluids and tissues*
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Absorption Process: Passive Diffusion, Active Diffusion & Filtration - CORRECT ANSWER-*Passive
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Diffusion:* (the major process; does NOT require cellular energy)
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Occurs across a *concentration gradient.*
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