PHA2022 Chap.3 Drugs of Abuse, Tolerance and Dependence
Drugs of Abuse, Tolerance and Dependence
Drugs of abuse are studied through pharmacology, learning, adaptation and context. Reward and reinforcement are related but not identical to subjective pleasure. A consequence reinforces a behaviour when it increases its future probability.
Relief from withdrawal or distress can negatively reinforce use even when the immediate experience is not described as pleasurable.
Repeated exposure can produce pharmacodynamic tolerance through receptor and signalling adaptation, pharmacokinetic tolerance through faster drug handling, and behavioural tolerance through learned compensation.
Tolerance can be effect specific: desired effects, impairment and respiratory depression may adapt at different rates. Increasing dose to recapture one effect can therefore narrow safety margins.
Dependence is adaptation revealed when drug reduction produces withdrawal or impaired function. It can occur with medically supervised use and does not by itself establish addiction.
Harmful use and substance-use disorders involve patterns of impaired control, priority and consequence assessed under criteria and context. Moral labels obscure mechanisms and barriers to care.
Sensitisation is an increased response with repeated exposure and can coexist with tolerance to another effect. Craving or cue reactivity may strengthen while a subjective effect diminishes.
Dose, interval, route and context influence which adaptation is observed. A single word such as tolerance cannot stand in for the measured outcome.
Conditioned cues can evoke expectation, craving or compensatory responses. A familiar administration context may trigger physiological compensation that reduces the observed drug effect.
Taking a prior dose in an unfamiliar context can remove some conditioned compensation and increase overdose risk. The mechanism is probabilistic and interacts with loss of pharmacological tolerance during abstinence.
Route of administration affects speed of delivery and reinforcement. Rapid brain exposure can create a close temporal link between behaviour and consequence. It can also increase peaks and acute harm.
Comparing routes requires dose, bioavailability and time course, not a simple hierarchy of badness. Formulation and co-use can alter the relation further.
Worked abstinence case: a person resumes a former opioid dose after a period without use. Pharmacological tolerance to respiratory depression has fallen, while memory of the prior dose and contextual habits remain. Unfamiliar setting or sedative co-use can add risk.
The safe analysis predicts reduced tolerance, uncertain potency and the need for evidence-based overdose prevention rather than blaming willpower.
Population and individual risk factors include availability, trauma, mental health, social connection, housing, legal conditions and access to treatment. These factors do not replace pharmacology; they alter exposure, reinforcement, vulnerability and recovery opportunity.
An integrated answer names the pathway instead of placing biology, psychology and society in unrelated lists.
Study the topic by separating terms, then rebuilding interaction. For every case, identify drug effect, time course, learned cue, behaviour consequence, adaptation and social condition. Change abstinence duration, route, context or co-use and predict the risk.
Finish with a harm-reduction or treatment response tied to the mechanism and evidence.
Withdrawal timing should be connected to pharmacokinetics and adaptation. A short half-life can produce rapid concentration decline and earlier symptoms, while a long-acting active metabolite can delay them. Severity is not determined by half-life alone; dose, duration, adaptation and individual condition matter.
Treatment evidence should be evaluated like other interventions, with defined outcomes and comparators, while recognising that engagement and continuity are shaped by stigma, cost and service access.
Use person-centred language and link proposed care to measured mechanisms, while leaving diagnosis and individual management to qualified current services.
What this chapter covers
- 01
tolerance
- 02
dependence
- 03
reinforcement
- 04
explain repeated drug use through reward, adaptation, learning, withdrawal and context without moral or single-mechanism shortcuts
- 05
Tolerance, dependence, harmful use and addiction overlap but are not interchangeable labels or moral judgements.
Explain post-abstinence overdose risk
- 1Name adapted effects.
- 1Assess abstinence interval.
- 1Add context and co-use.
- 1Predict exposure and response.
- 1Link prevention to mechanism.
Key terms
- tolerance
- Reduced response to the same dose after repeated exposure or a need for more exposure to obtain a prior response.
- dependence
- Adaptation in which stopping or reducing exposure produces a withdrawal syndrome or impaired function.
- reinforcement
- A consequence that increases the probability of the behaviour that produced it.
Drugs of Abuse, Tolerance and Dependence FAQ
What is the main reasoning task?
Explain repeated drug use through reward, adaptation, learning, withdrawal and context without moral or single-mechanism shortcuts.
What boundary matters?
Tolerance, dependence, harmful use and addiction overlap but are not interchangeable labels or moral judgements.
Are these official questions?
No. They are original AskSia practice aligned to the recovered 2026 unit.
How should I revise drug reasoning?
Draw the mechanism, work a changed dose, exposure, context or design, and state what evidence would reverse the conclusion.
Exam move
Retrieve the target or decision, trace concentration and time, work one changed case, then write the translational boundary.
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