Case 8 addiction
Chapter pinel
- Oral ingestion: Once they are swallowed, drugs dissolve in the fluids of the stomach
and are carried to the intestine, where they are absorbed into the bloodstream.
However, some drugs readily pass through the stomach wall (e.g., alcohol), and these
take effect sooner because they do not have to reach the intestine to be absorbed.
Drugs that are not readily absorbed from the digestive tract or that are broken down
into inactive metabolites (breakdown products of the body’s chemical reactions)
before they can be absorbed must be taken by some other route.
- Injection: Drug injections are typically made subcutaneously (SC), into the fatty tissue
just beneath the skin; intramuscularly (IM), into the large muscles; or intravenously
(IV), directly into veins at points where they run just beneath the skin. Many drug-
addicted persons prefer the intravenous route because the bloodstream delivers the
drug directly to the brain. However, the speed and directness of the intravenous route
are mixed blessings; after an intravenous injection, there is little or no opportunity to
counteract the effects of an overdose, an impurity, or an allergic reaction.
- Inhalation: Some drugs can be absorbed into the bloodstream through the rich network
of capillaries in the lungs. Many anesthetics are typically administered by inhalation,
as are tobacco and marijuana. The two main shortcomings of this route are that it is
difficult to precisely regulate the dose of inhaled drugs, and many substances damage
the lungs if they are inhaled chronically
- Absorption through mucous membranes: Some drugs can be administered through the
mucous membranes of the nose, mouth, and rectum. Cocaine, for example, is
commonly self-administered through the nasal membranes (snorted)—but not without
damaging them.
Drug tolerance
- Drug tolerance is a state of decreased sensitivity to
a drug that develops as a result of exposure to it.
Drug tolerance can be demonstrated in two ways:
by showing that a given dose of the drug has less
effect than it had before drug exposure or by
showing that it takes more of the drug to produce
the same effect
- One drug can produce tolerance to other drugs that
act by the same mechanism; this is known as cross tolerance.
- Drug tolerance often develops to some effects of a drug but not to others. tolerance
may develop to some effects of a drug while sensitivity to other effects of the same
drug increases. Increasing sensitivity to a drug is called drug sensitization
- there is no single mechanism that underlies all examples of it
- Drug tolerance that results from changes that reduce the amount of the drug getting to
its sites of action is called metabolic tolerance. Drug tolerance that results from
changes that reduce the reactivity of the sites of action to the drug is called functional
tolerance. Downregulation: decrease receptors on postsynaptic membrane. Cross
tolerance: developing tolerance for one drug can cross to similar substances
Withdrawal
- The effects of drug withdrawal are virtually always
opposite to the initial effects of the drug.
- Individuals who suffer withdrawal reactions when they stop
taking a drug are said to be physically dependent on that
drug. Show tolerance and withdrawal symptoms.
1
, Addiction
- Drug addicted individuals are those habitual drug users who continue to use a drug
despite its adverse effects on their health and social life, and despite their repeated
efforts to stop using it.
- Positive reinforcement: adding something to reinforce
- Negative reinforcement: take something away to reinforce.
Contingent drug tolerance
- Contingent drug tolerance refers to demonstrations that tolerance develops only to
drug effects that are actually experienced.
Conditioned drug tolerance
- Conditioned drug tolerance refers to demonstrations that tolerance effects are
maximally expressed only when a drug is administered in the same situation in which
it has previously been administered
- drug users become tolerant when they repeatedly self-administer their drug in the
same environment and, as a result, begin taking larger and larger doses to counteract
the diminution of drug effects. Then, if the drug user administers the usual massive
dose in an unusual situation, tolerance effects are not present to counteract the effects
of the drug, and there is a greater risk of death from overdose
- The central assumption of the theory is that conditional stimuli that predict drug
administration come to elicit conditional responses opposite to the unconditional
effects of the drug. Siegel has termed these hypothetical opposing conditional
responses conditioned compensatory responses. The theory is that conditional stimuli
that repeatedly predict the effects of a drug come to elicit greater and greater
conditioned compensatory responses; and those conditioned compensatory responses
increasingly counteract the unconditional effects of the drug and produce situationally
specific tolerance.
- Drug sensitization, like drug tolerance, can be situationally specific The difference is
that drug withdrawal effects are produced by elimination of the drug from the body,
whereas conditioned compensatory responses are elicited by drug- predictive cues in
the absence of the drug
Biopsychosocial research on addiction
- physical-dependence theories of addiction, physical dependence traps addicted
individuals in a vicious circle of drug taking and withdrawal symptoms. drug users
whose intake has reached a level sufficient to induce physical dependence are driven
by their withdrawal symptoms to self-administer the drug each time they attempt to
curtail their intake
- positive-incentive theories of addiction. They hold that the primary factor in most
cases of addiction is the craving for the positive- incentive (expected pleasure-
producing) properties of the drug.
- Moral model: blame the substance abuser for a failure of moral character or a lack of
self-control. Explanations of this sort often have a religious aspect and hold that only
divine help will free a person from addiction. Applications based on the moral model
can occasionally be effective.
- Disease model: the person who abuses drugs requires medical treatment rather than
moral exhortation or punishment. This view also justifies spending money to research
drug abuse in the same way that money is spent to research other diseases. A related
formulation of the disease model views drug abuse as a type of selfmedication, in
which the addict is drawn to specific drugs in an effort to compensate for a deficiency
of a corresponding endogenous substance: taking opiates to compensate for a lack of
2
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