Psychoactive Drugs Drugs that affect the brain, changing mood or behavior % of adults in North America use some kind of drug on a daily basis. The study of psychoactive drugs is called psychopharmacology.

Depressants – 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.

Stimulants 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.

Opiates 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)

Hallucinogens – 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

Cannabinoids – 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 PsychologicalPhysical

Psychological 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 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 cells Neurons alter function during drug use. Lower activity Greater activity Function differently

Withdrawal 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 drug Barbiturates or alcohol Sedation while being used. Excitability during withdrawal

Stimulant drug Cocaine or amphetamine Brain overactive (manic) while drug being used. Depression during withdrawal

Cross Dependence If physically dependent on one drug, Dependence transfers to similar drugs. Dependent on alcohol Cross dependent on barbiturates. Both sedatives

Managed withdrawal Cross dependence important for treatment. Dependent on heroin (illegal drug) Withdraw person gradually using morphine (legal).

Psychological Dependence Craving for repeated use because of drug’s rewarding effect. Learning. Pleasure circuits. Even psychological dependence has physical basis.

Tolerance Level of adaptation

Tolerance Loss of responsiveness to something. Noise; Traffic Drugs Takes more to get an effect. Develop tolerance to any drug.

Mechanisms for tolerance 1 Pharmacodynamic Action of drug on neurons First time, neurons most responsive With repeated use, tolerance develops.

Mechanisms for tolerance 2 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 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 Tolerance Tolerance develops to all drugs taken repeatedly Doses larger than prescribed Toxic dose Initial dose Effective dose Margin of safety

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 Tolerance Liver enzymes detoxify blood Break down drugs Liver damaged Tolerance lost More affected by drugs