Sources of DrugsNames of DrugsCategories of DrugsPsychoactive Drug ClassificationDrug IdentificationTypes of Drug EffectsDouble-Blind ProcedureDose-Response RelationshipsDose-Response CurveEstimating the Safety MarginTime-Dependent FactorsRoute of AdministrationTransport in the BloodBlood-Brain BarrierMechanisms of Drug ActionDrug InteractionsDrug DeactivationEnzyme InductionTolerance and Withdrawal SymptomsThe Actions of Drugs Sources of Drugs- Many drugs are chemically derived from plants Why do plants produce so many psychoactive drugs? Names of DrugsChemical Generic BrandDefinitionComplete chemical description of the moleculeOfficial (legal) name, listed in the United States Pharmacopoeia (USP)Specific drug or formulation trademarked by manufacturer-Can be patented for 20 yearsExample 2-[(diphenylmethyl)sulfinyl]acetamide modafinil Provigil®Categories of DrugsStimulants produce wakefulness, a sense of energy Depressants slow nervous system activityOpioids (narcotics) reduce pain Hallucinogens produce altered perceptionsPsychotherapeutics Treat symptoms of mental disorders- Some drugs belong in multiple categories Marijuana and nicotinePsychoactive Drug ClassificationDrug Identification- Importance of identification Physicians can tell from appearance the exact drug and dose- The Physician’s Desk Reference (PDR) includes photographs of pharmaceuticals - Illegal drugs are sometimes shaped, marked, or packaged in an identifiable way Example: MDMA (“ecstasy”)- Drugs can also be tested and identified through chemical analysisTypes of Drug EffectsNonspecific effects Specific effectsderive from the user’s unique background, expectations, perceptions, and environmentdepend on the presence of a chemical at certainconcentrations- Placebo effects are nonspecific Effects produced by an inactive chemical that the user believes to be a drug Important in treating pain and major depressionDouble-Blind Procedure- Neither the experimental participants nor the researchers know whether a subject is receiving an active drug or a placebo The blinding code is “broken” after drug trial is over - Necessity of double-blind experiments: Controls for nonspecific effects in order to evaluate the effectiveness of a drugDose-Response Relationships- Dose-response curve: graph depicting the relationship between a range of drug doses and the resulting drug effects- Threshold: the lowest dose at which an effect is observed- Different dose-response curves can be created for different drug effects Some response systems have higher thresholds Some drugs have an all-or-none dose-response relationshipDose-Response CurveEstimating the Safety Margin- Safety margin: the difference between:  Dose that produces the desired therapeutic effect in most patients Lowest dose that produces an unacceptable toxic reaction- Potency: Amount of a drug required to produce a given effect- Side effects: Unintended effects that accompany therapeutic effects- Effective dose: dose of a drug that produces a meaningful effect in some percentage of test subjects ED50 = effective dose for half the animals in a drug test- Lethal dose: dose of a drug that has a lethal effect in some percentage of test subjects LD50 = lethal dose for half the animals in a drug test - Therapeutic index = LD50/ED50 Always greater than one- Most drugs have an LD1 well above the ED95Time-Dependent Factors- The time course of a drug depends on: how the drug is administered how rapidly is it absorbed how it is eliminated from the body - Drug effects can be prolonged by taking additional doses at specific time intervals Intervals vary between drugs Taking multiple doses too close together will increase the maximum blood level of the drugo Possibly leading to cumulative effects Route of AdministrationOral administration- Relatively slow absorption the most complicated way to enter the bloodstream- Drugs must withstand digestive processes and pass through the cells lining the gastrointestinal tract into the bloodstream- Drugs then pass through the liver (where they may be metabolized)Insufflation(snorting)- Rapid onset of effects Absorption through the mucous membranes into the blood stream occurs rapidly- Bypasses the liver  no first-pass metabolismIntravenous injection- Rapid onset of effects the drug is delivered directly into the bloodstream- High concentrations can be delivered- Risks Irritating material may be injected Veins may become damaged over time Blood-borne diseasesSubcutaneous Injection- Under the skin- “Skin popping”- Risk: can cause necrosisIntramuscularinjection- Into a muscle - Absorption is more rapid from intramuscular injection due to the greater blood supply in muscles Inhalation - Rapid onset of effects- The drug moves from the lungs into the bloodstream through capillary walls Thus, the drug moves quickly from the lungs to the brain Transport in the Blood- Drug molecules attach to protein molecules The drug is inactive in this state The drug cannot be metabolized- Free (unbound) drug molecules can move to sites of action in the body The drug is active in this state- Drugs vary in their affinity for binding with plasma proteins A drug with high affinity will displace a drug with low affinityBlood-Brain Barrier- In general, only small lipophilic substances enter the brain Heroin is more lipophilic than morphine Thus, heroin is more potent- Many brain capillaries are covered with glia Also increasing the difficulty for compounds to pass out of the capillaries  Active transport systems may be needed to move chemicals in and out of the brain- Trauma and infections can impair the blood-brain barrier Permitting more chemicals to enter the brainMechanisms of Drug Action- Effects on specific neurotransmitter systems: Drugs may alter the availability of a neurotransmitter by changing the rate of:o Synthesiso Metabolismo Releaseo Reuptake Drugs may activate or prevent the activation of a receptorDrug Interactions- Combining alcohol and other depressants Respiratory depression- Combining stimulants and depressants Complicated interactions Example: o Methamphetamine lessens alcohol-related performance disruptionso Alcohol lessens methamphetamine-related sleep disruptionso Combination produces greater euphoriaDrug Deactivation- A drug ceases to have an effect when it is excreted unchanged from the body or is