Pharmacokineticsis
the
study
of
absorption, distribution, metabolism and excretion.
drug
“What the body does to the drug.”
Excretion- the elimination of unchanged drug or metabolite
from the body via renal, biliary, or pulmonary processes.
Drug=Pharmacon; Kinesis=Movement.
Pharmacodynamics- is the study of biochemical and
physiological effects of a drug and their mechanism of function
at organ system/sub-cellular/macro cellular levels.
“What the drug does to the body.”
Drug=Pharmacon; Dynamics=Power
PHARMACODYNAMICS
1. Onset of action- the time it takes to reach the minimum
effective concentration (MEC) after administering a drug.
2. Peak action- occurs when the drug reaches its highest blood or
plasma
concentration.
3. Duration of action- the length of time the drug has a
pharmacologic effect.
*Drug Receptor- any functional macromolecule in a cell to which a
drug
binds
to
produce
its
biological
effects.
1.
Agonistdrugs
that
produce
a
response.
2. Antagonists- drugs that blocks a response.
*Bioavaillability- refers to the percentage of the administered drug
dose that reaches the systemic circulation.
*Adverse Drug Reaction- The drug may have other effects on the
body besides the therapeutic effect.
The patient may be sensitive to the drug being given. The drug's
action on the body may cause other responses that are undesirable
or unpleasant. The patient may be taking too much or too little of
the drug, leading to adverse effects.
*Side
effectsa
nearly
unavoidable
drug effect produced at therapeutic doses.
Metabolism- the chemical conversion or transformation of drugs
into compounds that are easier to eliminate.
secondary
*Toxicity - adverse drug reaction caused by excessive dosing.
*Allergic Reaction- an immune response. Once the immune system
has been sensitized to a drug, re-exposure to that drug can trigger
an allergic response.
*Carcinogenic effect- refers to the ability of certain medications and
environmental chemicals to cause cancers.
*Teratogenic effect- a drug-induced birth defect
Physiological Effect of Drugs:
Primary Effect/ Therapeutic Effect- refers to desirable effect
Secondary Effect/ Side Effects- desirable or undesirable
PHARMACOKINETICS
LADME scheme- describes the pharmacokinetic processes that
follow a given dosage regimen.
Liberation- the release of the drug from its dosage form.
Absorption- the movement of a drug from the site of
administration to the blood circulation.
Distribution- the process by which a drug diffuses or is
transferred from intravascular space to extravascular space (body
tissues)
Liberation- the process of release of drug from the formulation
(pill, tablet, capsule). It is the dissolving of active drugs in Gl
fluids.
Example: enteric-coated aspirin slows absorption in the
stomach vs non-coated
Absorption (oral or parenteral)- A drug must be absorbed and
achieve adequate concentration at its site of action in order to
produce its biological effects.
Thus, when a drug is applied to a bodu's surface (e.g., G.l. tract,
skin, etc.), Its rate of absorption will determine the time for its
maximal concentration in plasma and at the receptor to produce
its peak effect.
*Pinocytosis- a process by which cells carry drug across their
membrane by engulfing the drug particles.
*Phagocytosis- or “cell eating”, is the process by which a cell
engulfs a particle and digests it.
Transport Mechanisms:
A. Passive Transport- occurs mostly by diffusion (movement
from higher concentration to lower concentration. Does not
require energy to move across the membrane.
B. Active Transport- a process that uses energy to actively move
a molecule across a membrane.
The movement of drug particles from the Gl tract to body fluids
by passive absorption, active absorption, or pinocytosis.
First pass effect/ Hepatic first pass- the process in which the
drug passes through the liver first.
Distribution- The blood, total body water, extracellular, lymphatic
and cerebrospinal fluids are involved in drug movement
throughout the body. Depending upon its chemical and physical
properties, the drug may be bound to plasma proteins or dissolved
in body fat, delaying its progress to its sites of action or excretory
mechanism.
Rights of Medication Administration:
Main Route of Drug Elimination: Kidneys through urine
Reminder:
Calculate the dose carefully
Do not leave a prepared drug unattended
Never give a drug that someone else has prepared
Identify patient properly
Other Route of Excretions:
1. Hepatic metabolism, bile, feces
2. Saliva, sweat, tears and breast milk
3. Lungs via exhaled air
Metabolism- This is how certain drugs are handled by the body
in preparation for their elimination and includes the fate of
drugs- biotransformation (e.g.. hydrolysis, conjugation,
oxidation- reduction).
Routes of Drug Administration:
Excretion: The kidney is the most important organ for drug
excretion but the liver, lung and skin are also involved in drug
elimination. Drugs excreted in feces are mostly derived from
unabsorbed, orally ingested drugs or from metabolites excreted
in the bile and not reabsorbed by the intestine.
Drug Administration Rules for Administration (Drug Route):
* Otic Route
* Sublingual and Buccal Routes
* Rectal Route
* Vaginal Route
* Oral Route
* Ocular Route
* Cutaneous Route
* Injection Routes
Half-life- the time it takes for one-half (50%) of the drug
concentration to be eliminated.
Reminder:
Give only drugs the doctor orders
Wash your hands
Prepare in a well-lit area
Focus on task; avoid distractions
Liver- primary site of metabolism