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1
Q

Pharmacokinestics

A

What the body does to a drug

2
Q

Pharmacodynamics

A

What the drug does to the body

3
Q

4 Pharmacokinetic properties that determine onset, intensity, and duration of drug action

A
  1. Absorption
  2. Distribution
  3. Metabolism
  4. Elimination
4
Q

Enteral adminitration

A

administering a drug by mouth; most common

Can be oral or sublingual/buccal

5
Q

Two types of oral preparations

A
  1. Enteric-coated preparations (ex. omeprazole, aspirin)

2. Extended-release preparations (ER or XR) (ex. morphine)

6
Q

Half life of morphine

A

2 to 4 hours; therefore, must be administered 6x per day to provide continuous pain relief

7
Q

Parenteral administration

A

drugs introduced directly in to the systemic circulation (ex. heparin poorly absorbed in GI tract; insulin unstable in GI tract)

8
Q

3 Major Parenteral Routes

A
  1. Intravenous (IV) - Ex. Rocuronium, a NM blocker
  2. Intramuscular (IM) - Ex. haloperidol, medroxyprogesterone
  3. Subcutaneous (SC) - Insulin and heparin
9
Q

Types of Administration Routes

A
Enteral (Oral, Sublingual/buccal)
Parenteral (IV, IM, SC)
Oral/Nasal inhalation
Intrathecal/Intraventricular
Topical
Transdermal
Rectal
10
Q

Desmopressin

A

Administered intranasally in the treatment of diabetes insipidus

11
Q

Oral Absorption Pattern

A

Variable; affected by many factors

12
Q

Intravenous Absorption Pattern

A

Absorption not required

13
Q

Subcutaneous Absorption Pattern

A

Depends on drug diluents:

  • Aqueous solution: prompt
  • Depot preparations: slow and sustained
14
Q

Transdermal (patch) Absorption Pattern

A

Slow and sustained

15
Q

Rectal Absorption Pattern

A

Erratic and Variable

16
Q

Inhalation Absorption Pattern

A

Systemic absorption may occur; this is not always desirable

17
Q

Sublingual Absorption Pattern

A

Depends on the drug:
Few drugs (ex. nitro) have rapid direct systemic absorption
Most drugs erratically or incompletely absorbed

18
Q

Oral Pros and Cons

A

+ Safest and most common; convenient, and economical route of administration

  • Limited absorption of some drugs; food may affect absorption, patient compliance is necessary, drugs may be metabolized before systemic absorption
19
Q

Intravenous Pros and Cons

A

+ immediate effects, ideal if dosed in large volumes, suitable for irritating substances and complex mixtures; valuable in emergencies, dose titration possible, ideal for high molecular weight proteins and peptide drugs

  • unsuitable for oily substances, bolus injection may result in adverse effects; most substances must be slowly injected, strict aseptic techniques needed
20
Q

Subcutaneous Pros and Cons

A

+ Suitable for slow-release drugs, ideal for some poorly soluble suspensions

  • pain or necrosis if drug is irritating, unsuitable for drugs administered in large volumes
21
Q

Intramuscular Pros and Cons

A

+ suitable if drug volume is moderate, suitable for oily vehicles and certain irritating substances, preferable to intravenous if patient must self-administer

  • affects certain lab tests (creatine kinase); can be painful, can cause IM hemorrhage (precluded during anticoagulation therapy)
22
Q

Transdermal (patch) Pros and Cons

A

+Bypasses the first-pass effect; convenient and painless, ideal for drugs that are lipophilic and have poor oral bioavailability, ideal for drugs that are quickly eliminated from the body

-some patients are allergic to patches, which can cause irritation; drug must be highly lipophilic, may cause delayed delivery of drug to pharmacological site of action, limited to drugs that can be taken in small daily doses

23
Q

Rectal Pros and Cons

A

+ partially bypasses first-pass effect, bypasses destruction by stomach acid, ideal fi drug causes vomiting, ideal in patients who are vomiting, or comatose

  • drugs may irritation the rectal mucosa, not a well-accepted route
24
Q

Inhalation Pros and Cons

A

+ Absorption is rapid; can have immediate effects, ideal for gases, effective for patients with respiratory problems, dose can be titrated, localized effect to target lungs: lower doses used compared to that with oral or parenteral administration; fewer systemic side effects

  • most addictive route (drug can enter the brain quickly); patient may have difficulty regulating dose; some patients may have difficulty using inhalers
25
Q

Sublingual Pros and Cons

A

+ Bypasses first-pass effect; bypasses destruction by stomach acid, drug stability maintained because the pH of saliva relatively neutral; may cause immediate pharmacological effects

  • limited to certain types of drugs, limited to drugs that can be taken in small doses; may lose part of the drug dose if swallowed
26
Q

Mechanisms of Absorption of Drugs from the GI tract

A
  1. Passive Diffusion
  2. Facilitated Diffusion
  3. Active transport
  4. Endocytosis and Exocytosis
27
Q

Factors influencing Absorption

A
  1. Effect of PH
  2. Blood flow to absorption site
  3. Total surface area available for absorption
  4. Contact time at the absorption surface
  5. Expression of P-glycoprotein
28
Q

pKa

A

Ionization constant; ratio between charged and uncharged forms determined by the pH at the site of absorption and by the strength of the weak acid or the weak base

29
Q

pKa relationship to acidicty

A

Lower pKa = more acidic

Higher pKa= more basic

30
Q

Distribution Equilibrium

A

permeable form of a drug achieves an equal concentration in all body water spaces

31
Q

Why do the intestines have more absorption than the stomach?

A

1000- fold surface area

Receives more blood flow

32
Q

When pH < pKa, what forms predominate?

A

Protonated forms of HA and BH+ predominate

33
Q

When pH> pKa, what forms predominate?

A

Deprotonated forms A- and B predominate

34
Q

P -glycoprotein

A

Transmembrane transporter protein responsible for transporting various mmolecules, including drugs, across cell membranes; transports drugs from tissues to blood (pumps drugs out of cells); multidrug resistance

35
Q

Where is P-glycoprotein expressed?

A

Tissues throughout the body including liver, kidneys, placenta, intestines, and brain capillaries

36
Q

Areas of high expression of P-glycoprotein ___________ drug absorption.

A

reduces

37
Q

Bioavailability

A

Rate and extent to which an administered drug reaches the systemic circulation; important for calculating drug dosages for nonintravenous routes of administration

38
Q

IV administration confers ______ % bioavailability.

A

100%

39
Q

Factors that Influence Bioavailability

A
  1. First-Pass Hepatic Metabolism
  2. Solubility of the drug
  3. Chemical Instability of the drug
  4. Nature of the drug formulation
40
Q

Bioequivalence

A

Two drugs formations are bioequivalent if they show comparable bioavailability and similar times to achieve peak blood concentrations.

41
Q

Therapeutic Equivalence

A

Two drug formulations show therapeutic equivalence if they are pharmaceutically equivalent (same dosage, same active ingredient, same route of administration) with similar clinical and safety profiles.

42
Q

What does clinical effectiveness depend on?

A

Both the max serum drug concentration and the time required (after administration) to reach peak concentration

43
Q

Drug Distribution

A

process by which a drug reversibly leaves the bloodstream and enters the interstitium (Extracellular fluid) and the tissues

44
Q

Distribution of the drug from the plasma to the intersititium depends on….

A
CO & Local Blood Flow
Capillary Permeability
Tissue volume
Degree of binding of the drug to plasma and tissue proteins
Relative lipophilicity of the drug
45
Q

Volume of Distribution (Vd)

A

fluid volume that is required to contain the entire drug in the body at the same concentration measured in the plasma

Vd = (Amount of drug in body) / (plasma concentration at time zero)

46
Q

Drugs with high molecular weight or is extensively protein bound gets trapped where?

A

Plasma Compartment (Ex. Heparin)

Low Vd that approximates plasma volume

47
Q

Drug has low molecular weight but is hydrophilic ends up where?

A

Extracellular Fluid (Ex. Aminoglycoside antibiotics)

It can pass through endothelial slit junctions of capillaries into interstitial fluid; hydrophilic drugs cannot move across lipid membranes into intracellular fluid

48
Q

Drug has low molecular weight but is lipophilic ends up where?

A

Total body water (ex. ethanol)

It can move into interstitium through slit junctions and also pass through cell membrane into intracellular fluid. 60% of body weight.

49
Q

An increase in Vd ______ the half-life and ________ the duration of action of hte drug.

A

Increases, extends