PSYCHOPHARMACOLOGY

• The scientific study of psychoactive drugs and their effects.

General Principles of Psychopharmacology

• 1. Drug use in of itself is neither good nor bad…it just is.

– Let’s study the phenomena objectively, without preconceived moral judgment.

• 2. All drugs have multiple effects– Therapeutic and side-effects may be context dependent..i.e. SSRIs may

be used as a sleep aid, or drowsiness may be seen as a side effect.

General Principles of Psychopharmacology

3. Drugs do not produce effects that are outside the organisms behavioral repertoire.– Instead they may magnify or diminish “normal behaviors, or alter

the probability or context of responses, etc..

4. Drug effects are influenced by “non-specific” factors– In many cases the environmental context may alter a drugs’ effects. The

physiological state and Psychological “set” of the individual may also have major influences.

Non-specific Factors

• “Set”

The physiological and psychological state of the user.

Setting

The environment and social context in which the drug is taken

Cigarettes to “get going” or to “chill out”

Non-specific drug effects cont’

The “Placebo Effect”

Effects NOT based on specific biological actions of the drug, but instead are produced in some way by the Expectations of the user.

Placebo Effect-

• Placebo- Latin for "I shall please.” • A placebo is an inert substance,..sugar pill..sham

medication • Typically about 35% + of subjects are responsive.• Has been effective in treating Pain, anxiety,

depression, etc. • Some people may even experience placebo side

effects/withdrawal

General Principles of Psychopharmacology

Drug Effects are influenced by “Pharmacokinetics

Pharmacokinetics

– the influences of route of drug administration, drug absorption, drug distribution, drug transformation, and drug elimination.

– These factors influence how fast and how much of a drug gets to its’ sites of action, as well as the duration of a drugs’ effects.

General Principles of Psychopharmacology cont’

• Psychokinetic studies clearly indicate that drug effects are:

• 5. Dose-dependent

– Consider the effects of mild coffee vs espresso!

General Principles of Psychopharmacology

• 6. Drug Effects are Time-Dependent– Consider early intoxication vs late

Early

Later

Way Late

Drug Effects are influenced by “Pharmacodynamics”

• Drug effects on the target tissue• psychoactive drugs produce effects in the central

nervous system (CNS)

– Many psychoactive drugs bind to “Neurotransmitter receptors”

• And alter the activity of brain cells ( neurons) and their functional relationships with other neurons

• More on this later

General Principles of Psychopharmacology cont’

• Pharmacodynamic studies clearly indicate that drug effects are:

• 7. dependent on the type of drug and its’ site of action

DRUG SITES OF ACTION (more when we cover the nervous system)

• Different Psychoactive Drugs affect different Neurotransmitter Systems in the Brain that in turn have different consequences for behavior, thought and mood.

Classical Neurotransmitters

• Acetylcholine– In the brain, it appears to be involved in

learning/memory, attention as well as sleeping and dreaming.

Classical Neurotransmitters cont’

Dopamine

• implicated in movement control– Parkinson’s Disease

• Dopamine excess may be involved in Schizophrenia.

• involved in the “reward system of the brain.”

Classical Neurotransmitters cont’

• Norepinephrine– primarily involved in control of

alertness/vigilance.– Possible involvement in mood state

Classical Neurotransmitters cont’

• Serotonin–plays a role in the regulation of mood

–It also has a role in the control of eating, sleep and arousal.

Classical Neurotransmitters cont’

• Endorphin/ Enkephalin– Modulates the experience of pain– Controls breathing and heart rate, cough reflex,

nausea and vomiting – Modulates feelings of euphoria and reward

Classical Neurotransmitters cont’

GABA– Most prevalent inhibitory neurotransmitter in

the brain– GABA secreted by “local” interneurons all over

the brain.– Implicated in relaxation/anti-anxiety

More on….

Pharmacokinetics

• Administration

• Absorption

• Distribution

• Biotransformation

• Excretion

DRUG

ABSORBED

DRUG

DISTRIBUTED

DRUG

ADMINISTERED

DRUG

METABOLIZED

DRUG

ELIMINATED

Routes of Administration• Oral

• Intramuscular (IM)

• Intraperitoneal (IP)

• Intravenous (IV)

• Inhalation

• Intracranial (IC)

• Intracerebroventricular

• Topical

Inhalation- a fast route

From lungs a direct shot to brain through carotid artery

Absorption

• Moving from the site of administration to the bloodstream– Drugs first travel in the bloodstream to get to sites of

action– How fast do drugs leave the site of administration?

• Route• Acidity/Alkalinity

• Absorption relates to bioavailability– The amount of the drug that reaches the bloodstream

and/or site of action

Distribution

• Refers to factors influencing a drug’s ability to get to its site of action after absorption– First Pass effect

• Depends on route of administration

– Protein Complexing

Role of the Liver in the “First Pass Effect.”

INTRAVENOUSINJECTION

INTRAMUSCULARINJECTION

ORAL

INHALATION

LIVER

INTESTINE

LUNGS

BRAIN

RIGHTSIDEOFHEART

LEFTSIDEOFHEART

Protein complexing

Proteins in the bloodstream may bind to the drug and slow or prevent its distribution

Distribution-Depot binding

Bone, Fat, Muscle, non-specific binding of drug ..affects distribution

Distribution-Blood-brain barrier limits drug access to brain

Biotransformation/MetabolismDrug Metabolization – Enzymes break down the drug

molecules to prepare them for ELIMINATION

Biotranformation occurs mainly in LIVER, but can occur in the nervous system, or in the blood stream as well

Enzymes break down drugs into metabolites Metabolites can be active or inactive

Some drugs are not transformed at all..