potentcy and efficacy

ED50 maintenance, loading doses

theraputic index

Potency

the amount of drug that must be given in order to produce a particular response- its relative pharmacologic activity- is called the potency of the drug….so a drug that is highly potent requires only a little amount to produce its effect. The affinity of a drug is related to its potency….drugs with high affinity for a receptor need little drug to bind to the receptor and are thus highly potent drugs. P51

Efficacy

how well a drug produces its desired effect is called its efficacy…the efficacy of a drug is related to its intrinsic activity….drugs with high intrinsic activity have greater efficacy p51 (potency is not efficacy!!! Do not confuse!!!)(two drugs can have different potency but same efficancy)

Therapeutic index

the relation of ED50 and LD50 is called the therapeutic index…therapeutic index can be explained by this equation, where TI represents the therapeutic index:   p52

       ED50

                             TI= ----------

                                    LD50

ED50 is 99 mg and the LD50 is 100 mg then the TI is 0.99 which is rounded to 1.00

When the ED50 and the LD50 do not differ by much ten the drug is considered to have a narrow index.

PharmicoTheraputics

PharmicoKenetics

Pharm- Dynamics

Pharmacotherapeutics

the achievement of the desired therapeutic goal from drug therapy

It is the indications and therapies a drug are given!!!!

Indications and therapies are often interchangeable for pharmacotherapeutics

Can be used to induce a cure

Generally pharmacotherapeutics of a drug is determined through clinical drug trials

Pharmacokinetics (4 areas)

A. D. M. E

absorbtion, distribution, metabolism, excretion

p 40 is the movement of the drug particles inside the body and the processes that occur during this movement

Absorption

Distribution

Excretion

Metabolism

is the conversion of the drug into another substance or substances

More explanation is on p 45

P- 450 system

also called cytochrome P-450 system, microsomal enzymes specific liver enzymes

Liver metabolism is predominantly achieved by specific liver

This system is a combination of several types of cytochromes called families

Only three families are involved in drug metabolism: CYP1, CYP2, CYP3

The other enzymes in the P-450 group metabolize naturally occurring enzymes such as fatty acids

….more on p 46….

Steady state

is a steady level of drug in the blood stream… it is a point at which the amount of drug being administered and the amount being eliminated balance off…this balance means that what comes in equals what goes out

4-5 half lives

Clearance

p 49 a pharmokinetic concept….several pharmacokinetic factors work together to affect the rate at which drug molecules disappear from the circulatory system …the rate is called clearance…the clearance rate of a drug….

Renal and hepatic metabolism is the major modes of clearance

Some drugs are primarily cleared by one mechanism rather then the other

Other drugs the two mechanisms are both actively involved in clearance

Gender effects patients clearance:

Women more rapid….clozpine, erythromycin, theophylline

Men more rapidly…lorazepam, acetaminophen, and digoxin

Slower clearance means that the drug particles stay in the circulation longer, increasing the half life and the potential for increased therapeutic and adverse effects from the drug

Pharmacodynamics

p 49 is the biological, chemical, and physiologic actions of a particular drug within the body and the study of how those actions occur

Pharmacodynamics is how the Drug acts to the body!!!!

Receptor

:p 49 cells in the body have receptors…most drugs create their effects in the body by attaching to special sites called receptors!!! At the receptor site the drug is able to stimulate the cell to act in a way that the cell is designed to act

Drug molecules only attach to certain receptor sites producing a particular effect in the cell…the drug stimulates the cell to act in a way the cell was designed to act…drugs do that by attaching to to the body’s receptors for intrinsic elements such as hormones, neurotransmitters, and other internal methods of regulating cell function

1. glomular filtration- protein bound wont be excreeted

2. passive tubular reabsorption- particles move along their concentration gradient

3. active tubular secretion- active transport out

* the intensity of a drugs resonse is directly related to the number of receptors occupied

* max response occurs when all the receptors have moleculesattached

different drugs have different strengths of attraction or affinity for sites

once a drug is attached to a receptor it has different abilities to stimulate the receptor

minimum effective concentration

amount of drug needed to have a response

Intrinsic activity

Is a drug interaction that affects pharmacodynamics

p 60 it occurs when two or more “like” drugs (in terms of therapeutic effect) are combined, and the result is the sum of the drugs’ effect

If written as an equation the concept looks like this:

1 ( Drug A) = 1 (Drug B) = 2

AN Additive effect may be intentional or may be unintentionally cause harm

(two examples of Codeine and Alcohol….p 60)

Is a drug interaction that affects pharmacodynamics

p 61 occurs when two or more “unlike” drugs (in terms of therapeutic effect or mechanism of action) are used together to produce a combined effect, and the outcome is a drug effect greater than either drug’s activity alone.

  The concept equation looks like this:
1 (Drug A) + 1 (Drug B) = 3

 Just like a n additive interaction, a synergistic interaction may be intentional or may intentionally cause harm

 an interaction in which the effect of only one of the two drugs is increased

 Equation Concept looks like this:

½ (Drug A) + 1 (Drug B) = 2

 Potentioned Effect  Is a drug interaction that affects pharmacodynamics

 A drug of mild effect enhances the effect of the second drug

 Example p 61

Is the opposite of synergist effect

 Is a drug interaction that affects pharmacodynamics

 It results in a therapeutic effect that is less than the effect of either drug alone because the second drug wither diminishes or cancels the effects of the first drug

 Concept equation :
1 (Drug A) + 1 ( Drug B) = 0

 Example p 61…..

1. health status

2. age and gender

3. lifestyle diet and habits

4. environment

5. culture and traits

United states pharmacopeia national formulary (1820)

* current authoratative source for drug standards

* revsied every 5 yrs

* high standards

* came about because of meat packing industry (unsanitary)

* required labels on drugs

* designated USP as authority

* came about becasue of sulfanamide deaths

* Establish the FDA for testing and labeling prior to sales

* after Thalidomide caused birth defects in EU the USA tighten controls and testing on drugs

• established FDA
• established drug schedule catagory
• C1- heroine no use, limited research
• C2- morphine (reqs precription type, no phone ins, refill needs no Rx)
• C3- other narcs (written/phone order ok, 5 refilles q 6 months)
• C4- benzos etc (same as above)
• C5- antidiarrhea (some OTC)

ENTERAL = Enters your body with food... PO

PARENTERAL= anything with a needle

TOPICAL= technically another parental bc it bypasses GI

Wierd PO Forms

Troches

Syrups

Elixers

Emulsions/Suspensions

Troches- lozenges

Syrups-   65 % sugar

Elixer-     alcohol mixture

Emulsions- 2 liquids that dont mix (oil and water)

Suspension- finely divided solid in a liquid