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what is the movement of drugs through the body?
what 5 things does pharmacokinetics relate to?
- drug's absorption
- distribution in the body
- distribution to site of action
- metabolism of drug
- excretion of drug
what are the 3 properties that influence movement
- molecular size
- lipid solubility
- degree of ionization depends on pH of site
______ molecules are lipid soluble and pass through biologic membranes easiliy
_____ drugs are water soluble and must pass through water pores of the biologic membrane or be transported through the membrane by specialized transport mechanisms
ionized drug movements depend on 3 types of transport?
- passive diffusion
- specialized transport mechanism
what are two types of specialized transport mechanisms?
- facilitated diffusion
- active transport
what is the process where small water soluble substances may pass through aqueous channels or water pores in cell membranes?
nonionized forms of drugs readily cross biologic membranes along a concentration gradient until equilibrium is reached, this is known as?
how do large ionized water soluble drug molecules cross the biologic membrane?
specialized transport mechanisms
what process is it when a drug forms a complex with a component of the cell membrane and is carried through the membrane and release?
what process is the movement of drug molecules across biologic membranes against both a concentration and an electrochemical gradient?
what form of specialized transport requires energy?
what are the six factors that influence absorption?
- degree of ionization
- formulation (liquid or solid)
- circulation to area
- area of absorptive surface
- route of administration
what can delay dissolution of tablets until they have moved from the stomach?
what two ways are routes of administration classified?
what type of drug is placed directly into the GI tract by oral or rectal administration?
what is the safest, most common and convenient enteral route of administration?
____ _____ _____ may reduce concentration of drug molecules
first pass effect
what is it called when a drug is removed from the liver and has a low bioavailability?
_____ drugs bypass the GI tract and include various injectable routes
what are five examples of parenteral drugs?
- intravenous IV
- subcutaneous SC
- intramuscular IM
- topical routes
what are two examples of topical routes of parenteral drugs?
- transdermal patch
what are the 5 features of IV route?
- bypasses absorption
- most predictable route
- used in emergency situations
- less safe than oral route
- injection site reactions possible
drug distribution is achieved primarily through?
the circulatory system
which organs receive the drug minutes after absorption?
what may affect the duration of a drug effect?
what are four ways drugs are distributed?
- plasma protein
- blood brain barrier
- placenta as barrier
t/f a bound drug to a plasma protein may cross the membrane
false only a free or unbound drug is capable of crossing biologic membranes
where does the majority of metabolism occur?
why does metabolism happen most frequently in the liver?
because it contains the greatest diversity and quantity of metabolic enzymes
phase I and phase II are collectively referred to as what?
what does biotransformation refer to?
phase I and phase II processes
what four ways can biotransformation alter drugs?
- convert an active drug to an inactive drug
- convert an active drug to an active or toxic metabolite
- convert an inactive drug to an active drug
- convert an unexcretable (more lipophilic) drug into an excretable (more hydrophilic) metabolite
during phase I reactions a drugs chemical structure is modified through what?
oxidation, reduction or hydrolysis
what is the most commonly used pathway for phase I reactions
hepatic microsomal cytochrome P450 (CYP450)
during phase II reactions the chemical structure of a drug is modified how?
by conjugation to a large polar endogenous molecule
why is CYP450 induced or inhibited and what is it responsible for?
- induced to increase drug metabolism
- inhibited to reduce the rate of drugs metabolism
- responsible for many adverse drug-drug interactions
what is the most common means to eliminate drug molecules?
what is the most important mechanism of drug elimination from the body?
what two ways does glomerular filtration work?
- active tubular secretion
- passive tubular secretion
what is the movement of drugs from the bloodstream into renal tubular fluid by a nonselective carrier system?
active tubular secretion
what is it called when drugs need to be retained by the body and the pH of the urine is manipulated?
passive tubular reabsorption
what is it called when metabolites in bile are hydrolyzed and reabsorbed from the gut and the drug action can be reestablished?
what is exhalation used for during excretion?
elimination of anesthetic gases and vapors
what is the removal of most drugs from the body follows an exponential or first order kinetics (implies that a constnat fraction of the drug is eliminated per unit of time)
half-life of a drug
what is the plateau level of drug accumulates and involves over four half lives to eliminate the drug?
steady state concentration
how many half lives does it take to eliminate a drug from the body?