Concepts in Pharmacology Flashcards
Half-life
The rate at which the body metabolizes the drug, which in turn affects how long it takes for the drug to achieve a steady state, the point at which its blood concentration no longer fluctuates wildly with each additional dose of medication.
Pharmacodynamics
The interaction of the drug with the body to elicit a clinical effect and includes such concepts as potency, efficacy, and dose responsive curves.
Pharmacokinetics
The route of drug entry into the body (oral, intravenous or nasal) and the absorption, distribution, metabolism, and elimination of the drug.
Route of administration
Is the first point at which a drug interacts with the body. Mouth, rectum, spinal fluid, skin, nasal cavity and lungs).
Distribution
Dependant upon drug permeability and blood flow to different organs. Lipid solubility is particularly important in determining which drugs can enter the brain.
Protein binding
A potential source of drug-drug interactions as drugs can displace each other from protein bound positions increasing the amount of unbound drug.
The kidney
Involved in the excretion of the water soluble metabolites of most drugs. While nearly all of the drugs used in pharm are metabolized through the liver, two important exceptions are excreted in unchanged forms by the kidney. Lithium and gabapentin.
Potency
Potency is the amount of drug necessary to produce a certain effect. In psychopharmacology, this is often related to the efficiency with which a drug binds to its receptors.
Efficacy
Distinct from potency, efficacy refers to a drug’s maximum possible effects, not to the amount of drug required to produce a given effect.
Drug concentration measurement
Related to both pharmacokinetics and pharmacodynamics is the measurement of plasma drug concentrations. For many drugs it is possible to measure the concentration of the drug in blood. Even though drug concentrations are not measured routinely for the many of the drugs used in psychopharmacology, several drugs do require regular measurements, such as lithium and in some cases tricyclic antidepressants.
Tolerance
Generally refers to the need for higher doses to obtain the same effect or loss of a drug effect at the same dose, be it a therapeutic effect or the induction of euphoria from illicit drugs. Tolerance can also occur as a result of pharmacodynamic changes, in which something in the body is changing in response to the drug.
Dependence
The physiological or psychological need to continue to take the drug. Physical dependence results in a withdrawal syndrome when the dose of the drug is decreased or the drug is withdrawn altogether. Withdrawal syndromes exist for many drugs relevant to psychopharmacology including alcohol, opiates, and some antidepressants.
