Psychoactive DrugsPsychoactive Drugs

Drugs that affect the brain, changing mood or behavior.

• 80-90% of adults in North America use some kind of drug on a daily basis.

• The study of psychoactive drugs is called psychopharmacology.

DepressantsDepressants

• – e.g. Barbituates; benzodiazepines (e.g. Valium); alcohol.

• Reduced anxiety; feeling of well- being and lowered inhibitions;

• slowed pulse & breathing; • lowered blood pressure; • Poor concentration/ confusion or fatigue;

impaired coordination, memory or judgment; • respiratory depression or arrest.

StimulantsStimulants

• Stimulants– e.g. ephedra; • amphetamine; MDMA; • methylphenidate (Ritalin); cocaine• nicotine; caffeine. • Increased heart rate and blood pressure.• Increased metabolism; reduced appetite;• feelings of exhilaration, increased mental

alertness; • irritability/ anxiousness.

OpiatesOpiates

• Opiate and Morphine derivatives • – e.g. opium; morphine; codeine; thebaine. • heroin, oxycodone (OxyContin)• – Pain relief; euphoria; drowsiness;

respiratory• depression & arrest; nausea; confusion; • sedation (unconsciousness, coma)

HallucinogensHallucinogens

– e.g. LSD; mescaline; psilocybin.

• – Altered states of perception & mood

• nausea; increased body temperature; insomnia; weakness; tremors.

• risk of chronic mental and perception disorders.

Peyote: source of mescaline

CannabinoidsCannabinoids

• – e.g. hashish & marijuana • Euphoria; slowed thinking

and reaction time; • confusion; impaired balance

and coordination; • Impaired memory or learning• increased heart rate • anxiety; panic attacks

Dependence Dependence

Psychological Physical

Psychological DependencePsychological Dependence

• Craving for the repeated or compulsive use of a drug because its effects are deemed pleasurable

• Rewarded by effects• Positive reinforcement• Behavior shaped by seeking

pleasure• Activating reward circuits in brain

Physical DependencePhysical Dependence

• Dependence of the body tissues• Revealed by life threatening

withdrawal symptoms• Degree of dependence unknown

while drug use continues• Magnitude of withdrawal related to

amount of previous drug use

Adaptation of cellsAdaptation of cells

• Neurons alter function during drug use.

• Lower activity• Greater activity• Function

differently

WithdrawalWithdrawal

• Stop taking drug.• Brain rebounds.• If brain sedated by

drug, withdrawing brain will be overexcited.

• If brain excited by drug, withdrawing brain will be sedated.

Sedative drugSedative drug

• Barbiturates or alcohol

• Sedation while being used.

• Excitability during withdrawal

Stimulant drugStimulant drug

• Cocaine or amphetamine

• Brain overactive (manic) while drug being used.

• Depression during withdrawal

Cross DependenceCross Dependence

• If physically dependent on one drug,

• Dependence transfers to similar drugs.

• Dependent on alcohol• Cross dependent on

barbiturates.• Both sedatives

Managed withdrawalManaged withdrawal

• Cross dependence important for treatment.

• Dependent on heroin

(illegal drug) Withdraw person

gradually using morphine (legal).

Psychological DependencePsychological Dependence

• Craving for repeated use because of drug’s rewarding effect.

• Learning.• Pleasure circuits.• Even psychological

dependence has physical basis.

Tolerance Tolerance

Level of adaptation

ToleranceTolerance

• Loss of responsiveness to something.

• Noise; Traffic• Drugs• Takes more to get an

effect.• Develop tolerance to

any drug.

Mechanisms for tolerance Mechanisms for tolerance 11

• Pharmacodynamic• Action of drug on

neurons• First time, neurons

most responsive• With repeated use,

tolerance develops.

Mechanisms for tolerance Mechanisms for tolerance 22• Drug disposition• Breakdown of drug by

liver.• Liver has enzymes to

detoxify blood.• More drug use leads to

increase in production of enzymes.

• Increase drug use to stay ahead of enzymes.

Initial ToleranceInitial Tolerance

• We all begin live with certain level of tolerance.

• Initial tolerance• Differs from

person to person.• High initial

tolerance is warning sign for addiction

Developed ToleranceDeveloped Tolerance

• Tolerance develops to all drugs taken repeatedly• Doses larger than prescribed

Toxic dose

Initial dose

Effective dose

Margin of safety

Cross Tolerance Cross Tolerance

• If tolerance develops to one substance in a class of drugs

• Tolerance will transfer to other substances in that same class

• Barbiturates and alcohol

Reverse ToleranceReverse Tolerance

• Liver enzymes detoxify blood

• Break down drugs• Liver damaged• Tolerance lost• More affected by

drugs