Drug Abuse

Munir Gharaibeh, MD, PhD, MHPE

Faculty of Medicine, The University of Jordan

April, 2014

Drug Dependance

• A condition in which the user has a compelling desire to continue taking the drug either to experience its effects or to avoid the discomfort of its absence.

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MHPE

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MHPE

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MHPE 4

Psychologic Dependence

Psychic dependence.Psychic craving. Compulsive abuse.

A condition characterized by an emotional or mental drive to continue taking the drug, the effects of which the user believes are necessary to maintain his sense of optimal well being.

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MHPE

Psychologic Dependence

• * Occurs when a drug affects the reward system of the brain.

• ** When the drug is withheld, adaptations in the brain reward system manifest as dysphoria and drug craving.

• *** Can occur even with drugs that do not produce tolerance and physical dependence.

• Cross DependenceApr 21, 2023 6

Munir Gharaibeh MD, PhD, MHPE

Physical Dependence

Physiological DependenceAdaptive Dependence• Is an altered or adaptive physiologic state

produced in an individual by the repeated administration of a drug.

• Revealed only when the drug is abruptly withdrawn or when its actions are diminished by the administration of a specific antagonist.

• ** Results from many of the same mechanisms that produce tolerance.

• Cross Dependence

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MHPE

Tolerance

Decreased effect of a drug that develops with continued use. The dose- response curve shifts to the right as larger doses are needed to produce the same response.

• Tachyphylaxis.• Cross Tolerance.

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MHPE

Types of Tolerance

• A. Innate Tolerance:Interindividual variations in sensitivity to the drug that are present before its first administration( i.e. genetic variability in drug's receptors or pharmacokinetics).

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MHPE

Types of Tolerance

• B. Acquired Tolerance:• a. Pharmacokinetic• b. Pharmacodynamic:• **Changes in receptor number or a change in the

signal transduction pathway.• Short Term:• Inactivation (e.g. phosphorylation).• Internalization• Degradation• Long Term: • Gene regulation of protein (e.g.

adenelyl cyclase by morphine, glutamate receptor and synapses).

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MHPE

Types of Tolerance

• C. Learned Tolerance:• The drug produces

compensatory changes that are unrelated to its actions (i.e. Behavioral Tolerance and Conditioned Tolerance).

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MHPE

• Tolerance and physical dependence are normal physiologic adaptations to the continued use of a drug.

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MHPE

Addiction

Changes in neuronal pathways that cause the individual's priorities to be centered on harmful or compulsive drug –seeking and drug –using behaviors at the expense of normal medical and social interactions.

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MHPE

Addiction

A maladaptive pattern of substance use leading to clinically significant impairment or distress associated with any of a number of symptoms.

• Usually for nonprescription drugs, e.g. Nicotine and alcohol.

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MHPE

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MHPE 15

DSM-IV Dependence Criteria

Tolerance Withdrawal Use in larger amounts or for longer than intended Desire to cut down or control use Great deal of time spent in obtaining substance

or getting over effects Social, occupational, or recreation activities

given up or reduced Use despite knowledge of physical or

psychological problem

Drug Misuse

Commonly refers to the improper use of prescribed compounds or the use of such compounds for nontherapeutic purposes. e.g. Morphine and benzodiazepines.

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MHPE

Mechanisms of Physical Dependence

Typically results from mechanisms similar to those that produce pharmacodynamic tolerance.

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MHPE

Mechanisms of Psychological Dependence

Reward Sites in the Brain:• Ventral Tegmental Area (VTA)

directly projects dopaminergic neurons to Nucleus Accumbens (NA) through the Medial Forebrain Bundle.

• Repeated administration of a drug will cause adaptations of these reward pathways, which would be unmasked upon cessation of the drug.

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MHPE

Mechanisms of Addiction• Was thought to be mainly due to physical

and psychological dependence.• Cravings can persist long after symptoms of

withdrawal have abated.• Relapses are possible after years of sobriety.

i.e. it is an interplay between reward circuitry and memory circuitry in the brain.

• Cocaine and amphetamines are highly addictive but produce few symptoms of physical dependence.

• Addicts strive for the euphoregenic experience of the high.

• Addiction is due to a long-lasting change in the underlying brain reward system and/or memory systems related to the reward system.Apr 21, 2023 20

Munir Gharaibeh MD, PhD, MHPE

Variables Affecting Development of Addiction

The Drug:• Ability to produce

psychological dependence.• Pharmacokinetic properties:

Short ActingRapid ActingHigh Peak

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MHPE

Variables Affecting Development of Addiction

The Individual:• Genetic Influences: at least in

alcoholics.• Personality Differences: Risk-

Taker vs Risk- Aversive

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MHPE

Variables Affecting Development of Addiction

The Environment:• Societal Attitude• Cost• Availability

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MHPE

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MHPE