15.1 Basic Principles of Drug addiction Flashcards
What are the four routes of drug administration
- oral injestion
- injection
- inhalation
- mucuous membrane absorption
explain the process of oral ingestion
drugs dissolve in the stomach fluids and are then carried into the intestine, absorbed into blood stream
what are the two ways that oral ingestion can be irregular?
- some drugs do not have to pass into the intestines bc they can permeate the stomach wall
- some drugs are not easily absorbed by the digestive tract, or are broken down into inactive metabolites, and won’t have any or very much effect
what are the two main advantages of oral ingestion?
- Ease
2. Relative safety
what is the main disadvantages of oral ingestion?
- unpredictability - absorption from GI to blood can be influenced by hard to gauge factors like the amount and type of food in the stomach
why is injection common in medical practice? (3)
- strong effect
- fast acting
- predictable
what are the 3 methods of injection
- Subcutaneously (SC) - into fatty tissue under the skin
- intramuscularly (IM) - into large muscles
- Intravenously (IV) - directly into veins where they run beneath the skin
which is the typically preferred method of injection Among drug addicts
- why and why is it a problem (2)
intravenous, bc the blood brings it straight to the brain
- speed and directness also means its very difficult to counter act an overdose, an impurity or an allergic reaction
- can develop scar tissue, infections and collapsed veins are the few acceptable injection sites
explain inhalation
absorption through he capillaries in the lungs
what are the two main problems with inhalation
- difficult to regulate dose precisely
2. damage to lungs with chronic use
what is the main problem with mucous membrane absorption
damage to the membranes over time
what makes it difficult for potentially dangerous drugs to pass from the blood vessels of the CNS into the extracellular space?
the blood brain barrier
what are the two broad mechanisms of drug action?
- diffuse action across neural membranes in the CNS
2. specific action
what are the three main mechanisms of specific drug action?
- binding to synaptic receptors
- influencing synthesis, transport, release or deactivation of a neurotransmitter
- influencing the chain of chemical reactions elicited in postsyn neurons by the activation fo their receptors
what ends the action of most drugs?
how?
what is this called?
enzymes synthesized in the liver
- stimulate the conversion of active drugs into their non active forms (known as drug metabolism)
what is the main way that drug metabolism inhibits their action?
prevents them from passing through lipid membranes so it can’t penetrate the BBB
what is an additional way that drug metabolism inhibits action
small amounts of some psychoactivve drugs are passed into urien, sweat, faces, breath and mothers milk
explain drug tolerance
state of decreased sensitivity to a drug that develops as a result of exposure
what are the two ways we can demonstrate tolerance?
what does this mean generally?
- given dose has less effect that it did before exposure
- takes more time to produce the same effect
- Dose - response curve has shifted to the right
what are the three important facts about specificity of drug tolerance
- Cross tolerance - one drug can produce tolerance o drugs with similar mechanisms
- Can develop to some aspects of a drug but not others, may even sensitize to some aspect overr time
- Noot a unitary phenomenon - no single mechanism that underlies all examples of it - several adaptive mechanisms
what are the two categories of drug tolerance
- metabolic
2. functional
explain metabolic tolerance
tolerance that arises from a decrease in the amount fo drug that reaches its specific activity site
explain functional tolerance
changes that reduce the reactivity of the sites of action to a drug
what constitutes the majority of tolerance to psychoactive substances?
functional tolerance
what are the examples of neural changes that promote tolerance?
What are causes many of these changes?
(3)
- reduce receptors for the drug
- decrease binding efficiency
- diminish or impact binding o the cell’s activity
- epigenetic mechanisms
what is a withdrawal syndrome
the adverse physiological reaction that can occur after significant amounts of a drug have been in the body for some period of time, and then suddenly eliminated
what are the effects of withdrawal syndrome?
what does this imply?
the exact opposite to the initial effects of the drug itself.
- that the effects of withdrawal are produced by the same neural changes that produce tolerance
what are people who suffer withdrawal reactions when they cease drug consumption called?
physically dependent to that particular substance
explain the theoretical mechanism of withdrawal syndrome
exposure to a drug produces compensatory changes in the NS that offset the drugs effects producing tolerance
- when the drug is eliminated, these compensatory changes manifest as withdrawal symptoms that oppose the initial effects of the drug
what does the severity of withdrawal symptoms depend on?
the particular drug in question, the duration and degree of exposure and the speed with which it was eliminated
- in general, longer exposure to greater doses follow by more rapid elimination produce more severe withdrawal
what defines a drug addicted individual
a habitual drug user who continues to use a drug despite its adverse effects on their health and social life, despite their repeated efforts to cease use
What differentiates addiction from physical dependence
addicted individuals may take drugs to prevent withdrawal symptoms, but this is clearly not the only reason - if it were, waiting out the withdrawal would result in their addiction being removed, but this is rarely the case
