After finishing this chapter, students should be able to:
Most drugs are derived directly or indirectly from plants.
The legal pharmaceutical industry is one of the largest and most profitable industries in the United States.
Brand names belong to one company; the generic name for a chemical may be used by many companies.
Most psychoactive drugs can be categorized as stimulants, depressants, opiates, hallucinogens, or a psychotherapeutic agent.
Drugs can be identified by the appearance of commercial tablets or capsules, in some cases by the packaging or appearance of illicit drugs, or by a variety of chemical assays.
Specific drug effects are related to the concentration of the chemical; nonspecific effects can also be called placebo effects.
Because each drug is capable of producing many effects, many dose-effect relationships can be studied for any given drug.
The ratio of LD50 to ED50 is called the therapeutic index and is one indication of the relative safety of a drug for a particular use or effect.
The potency of a drug is the amount needed to produce an effect, not the importance of the effect.
The time course of a drug's effect is influenced by many factors, including route of administration, protein binding in the blood, and rate of elimination.
The blood-brain barrier prevents many drugs from reaching effective concentrations in the brain.
Virtually all psychoactive drugs have relatively specific effects on one neurotransmitter system or more, either through altering availability of the transmitter or by interacting with its receptor.
The liver microsomal enzyme system is important for drug deactivation and for some types of drug interactions.
Drug tolerance can result from changes in distribution and elimination, from behavioral adaptations, or from changes in the responsiveness of the nervous system caused by compensatory (homeostatic) mechanisms. Physical dependence (withdrawal) can be a consequence of this last type of tolerance.
