Psyc 222 1st Edition Lecture 8Outline of Last Lecture The Actions of Drugs i. Sources of drugsii. Categories of drugsiii. Drug identificationiv. Types of drug effectsv. Estimating time safety marginvi. Time dependent factorsOutline of Current Lecture Route Of administration i. Oral administrationii. Insufflationiii. Intravenous Injectioniv. Other types of injectionv. transport in the bloodvi. blood brain barriervii. mechanisms of drug actionviii.factors determining behavioral impacts of drugsix. Tolerance withdrawal symptomsCurrent LectureTo facilitate absorption drugs that are weak bases (alkaloids) or weak acids are commonly administered in the form of a salt, a compound formed by ionic bond between a negative ion (anion) and a positive ion (cation). The pH of the local area determines the ratio of ionized to nonionized drugs in the area. i. Relatively slow absorption. The most complicated way to enter the bloodstream. Drugs must withstand digestive processes and pass through cells lining the gastrointestinal tract into the bloodstream. Drugs then pass through the liver,where they are metabolized.ii. Rapid onset of effects. Absorption through the mucus membranes into the blood stream occur rapidly. Bypass the liver. iii. Rapid onset of effects. The drug is delivered directly into the bloodstream. High concetration can be delivered. The risks are irritating materials may be injected, and veins may become damaged overtime which makes the person more acceptable to blood borne disease.iv. Subcutaneous Injection: under the skin, skin popping (can cause necrosis), intramuscular injection: into a muscle (absorption is more rapid from intramuscular injection due to greater blood supply in muscles). There is also sublingual, and transdermal patch. Inhalation causes a rapid onset of effects, moves from lungs into bloodstream through capillary walls. Moves quickly from brain to lungs.v. Drug molecules attach to protein molecules. If Drug is inactive it Cannot be metabolized. Free drug molecules can move to sites of action in the body. if the drug is active the drugs vary in their affinity for binding with plasma protein. Drugs with high affinity will displace drugs with low affinity.vi. In general only small liophillic substances enter the brain. Heroin is more lipophillic thn morphine, more potent. Many brain capillaries are covered with glia. Increasing differences 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 an impair the blood brain barrier permitting more chemicals to enter the brain.vii. Effects on specific neurotransmitter systems:synthesismetabolismreleasereuptakeDrugs may prevent the activation of receptorsviii.Synergism is the property of a drug interaction in which the combination effect of 2 drugs exceeds the effect of either drug administered alone. Potentiation is the property of a synergetistic drug interaction in which one drug is combined with another drug produces an enhanced effect when one of the drugs alone would have had no effect. Cross tolerance is a phenomenon in which tolerance that results from the chronic usr of one drug induces a tolerance effect with regard to a second drug that has not been used before.ix. Drug disposition (pharmacokinetic) tolerance. Increased metabolism or excretionreduces the effect of the subsequent dose. May be related to enzyme activity or alteration of urine pH. Behavioral tolerance. Drug may have the same biochemical effect. Reduced behavioral effect as drug user learns to compensate.Pharmacodynamic tolerance in which sensitivity of neurons may change afterrepeated drug use and may cause withdrawl