(den 1140) pharmacology: week 3 (chapter 2)

Potency

function of the amount of drug required to produce an effect

Efficacy

-Maximum intensity of effect or response that a drug can produce

-Administering more drug will not increase the efficacy of the drug

Therapeutic index

used to compare safety of a drug

Pharmacokinetics

study of how a drug enters the body, circulates within the body,is changed by the body, and leaves the body

Disruption can happen with a tablet’s….

outer coating

disintegration

contents break apart

disperson

spreading through stomach

dissolution

dissolved in solution

Bound drugs are

pharmacologically inactive

free drug

not bound to protein, active and can cause a pharmacologic response

blood brain barrier

preventative

half life of a drug

Time it takes for a drug to decrease in amount by half

understanding half life helps determine

the frequency that a drug needs to be taken

Onset

the time it takes for the drug to elicit a therapeutic response

duration

the length of time of a drug's effect

loading dose

initial dose has a higher amount

maintenance dose

amount of drug given at set intervals

Drug absorption depends on variables that influence drug movement into the circulation. These variables include

dosage form, site and route of administration and such physiochemical factors as passive diffusion, active transport and the process by which cells absorb the drug (pinocytosis)

A term used to quantify the extent of drug absorption is

bioavailability

distribution

transport of a drug in the body by the bloodstream to the site of action

A drug can only be freely distributed to extravascular tissue only if it is

not bound to protein
- If a drug is bound to protein it is generally too large to pass into tissues

The volume of distribution refers to

the size of a compartment that would be filled with a drug in the same concentration as that found in the body's plasma or blood.

The areas where the drug is distributed first are those that are

most extensively supplied with blood
- heart, liver, kidneys and brain

Areas of slow distribution are

muscle, skin and fat

The organ most responsible for the biotransformation of drugs is the

liver

Excretion of metabolized drugs typically occurs via the

kidney

biliary excretion

excretion of drugs by the intestines; drugs eliminated by this route are taken up the liver. released into the bile, and elimanted in the feces.

enterohepatic circulation

drugs in bile may be resorbed into the bloodstream, returned to the liver and again secreted in the bile
- last around longer in the body

Pharmacodynamics

The study of what the drug does to the body

therapeutic effect of a drug

a positive change in a faulty physiologic system

The effects that a particular drug has depends on the

cells or tissues targeted by the drug

There are three basic ways by which drugs can exert their mechanism of action:

receptor, enzyme, and non-specific interactions.

drug-receptor interaction

- drug binds to a receptor site
- pharmacologic response is produced

The degree to which a drug attaches and binds with a receptor is called its

affinity

Types of drug-receptor interactions

agonist, partial agonist, antagonist, competitive antagonist and non-competitive antagonist

agonist

a molecule that, by binding to a receptor site, stimulates a response

antagonist

counteracts the action of the agonist can be 1, competitive antagonist 2, non- competitive antagonist and 3 physiological antagonist

partial agonist

Medication that produces a weaker, or less efficacious, response than an agonist.

competitive antagonist

Drug competes with the agonist for binding to the receptor. If it binds, there is no response.

non-competitive antagonist

Binds to a site different from the agonist changing the receptor site; not allowing the agonist to bind

Enzymes

substances that catalyze nearly every biological chemical reaction in a cell

For a drug to alter a physiological effect it must inhibit the action of a specific enzyme. To do this the drug....

"fools" the enzyme into binding to it instead of its normal target cell. This protects these target cells from the actions of the enzymes.

Nonspecific interactions

- do not involve a receptor or an enzyme
- affect cell membranes and various cellular activities, like metabolism, without directly interacting with a particular molecule.

Tablet

Molded or compressed medicinal substance with inert binder included to make a hard mass (Acetaminophen tablet)

Capsule

Gelatin shell that disintegrates in water to administer solids or liquids (Tetracycline capsule)

Pill

Globular or ovoid dose form made by incorporating medicinal agents with other binders to make a plastic mass; obsolete

Lozenge, troche

Flavored dose form designed to be held in the mouth to dissolve or disintegrate slowly (Cough drop)

Suppository

Single dose medication in waxy or fatty conical or ovoid shape that liberates active ingredient after insertion into the rectum or vagina for local or systemic effects (Glycerin suppository)

Solution

One phase system of two or more chemical components (Saline water)

Elixir

Sweetened hydroalcoholic solution containing flavoring materials

Syrup

Nearly saturated aqueous solution of sugar (Dextromethorphan syrup)

Tincture

Alcoholic or hydroalcoholic solution of drugs (Iodine tincture)

Spirit

Solution of volatile substance in alcohol (Aromatic ammonia spirit)

Lotion

Liquid suspension that can be protective

Emulsion

Preparation of two immiscible liquids, usually water and oil, one dispersed as small globules in the other

Suspension

Dispersion containing finely divided insoluble material suspended in a liquid medium

Cream

Emulsions that contain an oily and aqueous phase; external phase aqueous

Ointment

Semisolid preparation for external use that is a consistency that can be applied by rubbing; external phase oily

Transdermal patch

A permeable polymer membrane backed with a drug reservoir designed to provide controlled release of medication over a given period after application to intact skin (Nitroglycerin, scopolamine, fentanyl, nicotine)

Aerosol spray

Solution of volatile liquids with a propellant that delivers drugs to area (Albuterol inhaler, foot spray)

Intradermal implant

Small pellets implanted under the skin that allows drugs to be released slowly

Micropump

An implanted pump that delivers drug via a needle (Insulin pump)

Oral route

most common and simplest, produces slower onset of action

Rectal route

used if a client is vomiting or unconscious, poorly and irregularly absorbed

Intravenous route

produces the most rapid drug response, absorption phase is bypassed

Intramuscular route

drug injected into the deltoid region or gluteal mass, high blood flow through skeletal muscles

Subcutaneous route

injection of solutions or suspensions into the subcutaneous areolar tissue

Intradermal route

injection of small amounts of drugs into the epidermis of the skin

Intrathecal route

injection of solutions into the spinal subarachnoid space

Intraperitoneal route

placing fluid into the peritoneal cavity where exchange of substances can occur

Inhalation route

used for either local or systemic effects, drug is deposited on the bronchiolar endothelium

Topical route

application of drugs to body surfaces such as skin, oral mucosa, and sublingually

Factors Affecting Drug Response: Patient compliance

- lack of understanding or lack of motivation, patients often take medication incorrectly or not at all.

-may result from faulty communication, inadequate patient education, or the patient's health belief system.

Factors Affecting Drug Response: Psychologic factors

- attitude of the prescriber
- placebo
- maximize the drug's effect by talking it up

Tolerance

Drug tolerance is defined as the need for an increasingly larger dose of the drug to obtain the same effects as the original dose or the decreased effect produced after repeated administration of a given dose of the drug.

When a patient becomes tolerant to one drug, tolerance to other drugs with similar pharmacologic actions occurs. This is termed cross-tolerance.

If tolerance develops, a normal sensitivity to the drug's effect may be restored by ceasing administration of the drug.

Tachyphylaxis is the very rapid development of tolerance, often within hours.

Pathologic state

Diseased patients may respond to the administration of medication differently than other patients

Time of administration

The time a drug is administered, especially in relation to meals, alters the response to that drug.

Sex

The sex of the patient can alter a drug's effect. Women may be more sensitive than men to certain drugs, perhaps because of their smaller size or their hormones. Pregnancy alters the effect of certain drugs. Women of child-bearing age should avoid teratogenic drugs, and the oral health care provider should determine whether the patient is pregnant before administering any agent.

Genetic variation

Many differences in patient response to drugs have been associated with variations in ability to metabolize certain drugs. This difference may account for the fact that certain populations have a higher incidence of adverse effects to some drugs—a genetic predisposition.

Drug interactions

A drug's effect may be modified by previous or concomitant administration of another drug. There are many mechanisms by which drug interactions may modify a patient's treatment.

Environment

The environment contains many substances that may affect the action of drugs. Smoking induces enzymes, so higher doses of benzodiazepines are needed to produce the same effect as compared to nonsmokers. Some chemical contaminants, such as pesticides or solvents, can have an effect on a drug's action.

Side effect

predictable, dose related, and acts on nontarget organs

Toxic reaction

predictable, dose related, acts on target organs, extension of the drug's pharmacologic effects

Allergic reaction

not predictable, not dose related

Idiosyncratic reaction

genetically related abnormal drug response.

Clark's Rule

(weight in lbs/150) x adult dose

Fried's Rule

(age in months/150) x adult dose

Acids and Bases

weak acids are better absorbed when the pH is less than the pKa,

weak bases are better absorbed when the pH is greater than the pKa.

unionized vs ionized

The uncharged part behaves like a smooth traveler, easily crossing through body membranes.

On the other hand, the charged part struggles a bit, finding it harder to pass through these membranes.