chapter 3 (how drugs work in body and mind) Flashcards
4 routes of drug administration
- oral administration
- injection
- inhalation
- absorption through skin/membranes
what is the safest way to administer a drug?
orally
what characteristic is necessary of drugs to pass through the fat membrane between the gastrointestinal tract and blood capillaries?
substances must be lipid-soluble (soluble in fats)
intravenous (i.v.)
into a vein. as injection, takes approx. 15 seconds.
intramuscular (i.m.)
into a muscle. as injection, usually into large muscle like upper arm, thigh, buttock. absorbed into bloodstream through capillaries serving muscle. takes longer than i.v.
subcutaneous (s.c./sub-Q)
underneath the skin. as injection, slowest method because of less abundant blood supply. only small amounts.
intranasal
into the nasal cavity.
inhalation
breathing in particles of the drug through smoke or vapours. faster than i.v., takes 5-8 seconds.
sublingually
applied under the tongue. absorbed through membranes of mouth.
transdermal patch
device attached to the skin that slowly delivers the drug through skin absorption.
biotransformation
process of changing the molecular structure of a drug into forms that make it easier for the body to excrete it. how urinary excretion begins, mostly through enzymes in liver.
metabolite
by-product resulting from biotransformation process. structurally modified forms of original drug.
enzyme induction
repeated drug taking results in greater production of liver enzymes that metabolize that drug and similar ones.
enzyme inhibition
repeated drug taking stops the action of specific liver enzymes and metabolism of drug slows down.
drug competition
drugs taken in combination occupy all available liver enzymes leaving excess drugs nonmetabolized & resulting in toxic levels.
elimination half-life
length of time it takes for a drug to be reduced to 50% of its equilibrium level in bloodstream. (original concentration level.)
latency period
an interval of time during which blood levels of a drug are not yet sufficient for a drug effect to be observed.
cross-tolerance
phenomenon in which the tolerance that results from the chronic use of one drug induces a tolerance effect with regard to a second drug that has not been used before. (ex: alochol, barbiturates, benzos.)
cross-dependence
phenomenon in which one drug can be used to reduce the withdrawal symptoms following the discontinuance of of another drug.
central nervous sytem (cns)
portion of ns consisting of brain and spinal cord.
peripheral nervous system (pns)
portion of ns consisting of nerves and nerve fibers that carry info to cns and outward to muscles and glands. breaks down into somatic and autonomic ns.
sympathetic nervous system
portion of autonomic ns that controls bodily changes that deal with stressful/emergency situations.
parasympathetic nervous system
portion of autonomic ns that controls bodily changes that lead to increased nurturance, rest, and maintenance.
neuron
specialized cell in the nervous system that receives and transmits info. where psychoactive drugs do their work.
action potential
electrical message generated at the cell body that moves down the axon and causes release of nt.
cerebral cortex (neocortex)
portion of forebrain responsible for higher level information processing.
presynaptic terminals
at end of axon where nt is released.
resting membrane potential
difference in electrical charge between the inside and outside of neuron (~ -70 mV) when neuron is not being stimulated or inhibited.
synapse
juncture between neurons. consists of presynaptic terminal, intervening gap, and postsynaptic terminal containing receptor sites on the receiving neuron.
neurotransmitter
chemical substance that a neuron uses to communicate info at synapse.
reuptake
process by which a nt is transported from synapse back up into presynaptic terminal.
glutamate
most common excitatory nt. glutamate receptors associated with actions of PSP and ketamine and feelings of drug craving.
gamma aminobutyric acid (GABA)
most common inhibitory nt. antianxiety and anticonvulsant drugs tend to facilitate activity of GABA receptors in brain.
ionotropic receptor (ligand-gated ion channel)
cell membrane receptor-ion channel complex that allows specific ions to pass when receptor is activated. effects are fast.
metabotropic receptor
cell membrane receptor that is linked to a G protein. activation results in production of a second messenger that can have variety of intracellular functions. slow changes.
agonist
substance that binds to a receptor site, like the endogenous neurotransmitter, and produces the same response.
antagonist
substance that binds to a receptor site and decreases or eliminates the effectiveness of the endogenous neurotransmitter,
acetylcholine
neurotransmitter active in the parasympathetic autonomic ns, cerebral cortex, and peripheral somatic nerves.
norepinephrine (noradrenaline)
neurotransmitter active in sympathetic autonomic ns and in many regions of the brain.
dopamine
neurotransmitter in brain whose activity is related to motor control, learning/memory/emotionality, and cravings. binds to metabotropic dopamine receptors.
serotonin (5-hydroxytrytophan/5-HT)
neurotransmitter in the brain whose activity is related to emotionality and sleep patterns.
endorphins
class of chemical substances produced in brain and elsewhere in body that act on same opiate receptors as morphine, heroin, and codeine.
endocannabinoids
brain-produced chemicals that mimic effects of active ingredient in marijuana and other cannabis products.
blood-brain barrier
specialized separation between the bloodstream and cns that keeps toxins and large molecules out of the brain.
nucleus accumbens
region in limbic system of brain responsible for the rewarding effects of many drugs of abuse. related to release of dopamine in this area.
placebo
any inert substance that produces a psychological or physiological reaction.
double-blind
procedure in drug research in which neither the individual administering a chemical substance nor the individual receiving it knows whether the substance is the drug being evaluated or an active placebo.
metabolic (dispositional) tolerance
over repeated administrations, drug facilitates the processes that the produce the drug’s biotransformations in liver.
cellular (pharmacodynamic) tolerance
receptors stimulated by drug over time become less sensitive or removed from synapse altogether (receptor down-regulation) or repeated blocking of receptors may increase number of receptors or amount of neurotransmitter released (receptor up-regulation.)
