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Pharm > Pharm- Pharmacokinetics > Flashcards

Pharm- Pharmacokinetics Flashcards

1
Q

Liberation

A

-Traditional (IR- immediate release)

Special

  • Enteric coated (release in intestines)- delayed release
  • Abuse resistant
  • ER, XR, SR, CR (released thru day)
  • Delayed release- needs certain conditions for release
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2
Q

Absorption

A
  • drug moves from site of admin to site of measurement in body ex: mouth-stomach-intestine-liver-blood
  • must be dissolved to penetrate membranes (rate limiting step: crossing membranes)
  • IV admin has zero absorption rate- fastest
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3
Q

Absorption factors

A
  • physical state (smaller better)
  • absorption surface -concentration (more better)
  • solubility/ binding
  • membrane permeability
  • vascularity/ blood flow
  • GI motility
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4
Q

Types of absorption

A

Passive diffusion -gradient driven/ rate dependent on gradient

Active transport -pumps -transport protein (subject to inhibition/induction)

facilitated diffusion -conformational changes of membrane proteins

Endocytosis -large molecule “swallowed” into cell

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5
Q

Distribution

A
  • transfer of drug to and from body compartments
  • mvmnt of free drug (molecules not bound to proteins)
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6
Q

Volume of distribution

(amount of drug outside of blood in high cncntrn.)

A

Factors that affect:

  • plasma prot. binding
  • metabolism

active transport by target organs

  • intracellular binding
  • pH
  • fat (lipophilicity)
  • membrane permeability
  • storage

* lipophilic drugs “sit” in fat- leak out slowly back into system*

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7
Q

Distribution

A

Efflux pumps/ transport system

  • P-glycoprotein: liver, intestines, kidney, BBB/BTB
  • pump drug out of cells
  • tumor cells produce

Paracellular transport via capillary membrane

  • tissue pentration without crossing lipid bilayer
  • dependnt on blood flow
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8
Q

Distribution / BBB

A
  • brain needs protected environment (BBB)
  • protect/ maintain homeostasis
  • brain capillaries- tightly joined- fatty barrier (glial sheath)
  • drug leaving brain capills. has to cross capill wall and astrocyte membrn
  • high ionized drugs penetrate poor
  • fat soluble drugs penetrate rapidly
  • drugs that target CNS must be lipid soluble to reach brain target site
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9
Q

Metabolism

A

What is it?

-transformation of one chemical to another

Why is it occur?

-so body can get rid of drug

Where does it occur?

-mostly in liver-metabolism happens in every tissue

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10
Q

Drug metabolism

A

Outcomes:

  • Drug to interactive molecule
  • Drove to active molecule
  • Drove to multiple molecules (Active/inactive)
  • No metabolism (Eliminated unchanged)
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11
Q

Phase 1 reactions

A

-Introduces Polar functional group (-OH/-NH2)

Oxidation: Involve cytochrome P450 Enzymes

  • 75% of drug metabolism
  • CYP450 Enzymes involved in many biologic functions (Steroid hormone synthesis)

Effects on pharmacologic activity:

  • Decrease (typical metabolism)
  • Increase (some drugs- prodrugs need metabolism to become active

*One drug can have multiple metabolites (active/ inactive/ toxic)

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12
Q

Cytochrome P 450 (CYP450)

A

Enzyme system composed of heme-containing isozymes

  • 3A4
  • 2D6
  • 2C9
  • 2C19
  • 2E1
  • 1A2

Drug me to the substrate of more than one isozyme

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13
Q

Polymorphisms affect metabolism

A
  • Ultra rapid (low serum concentration)
  • Poor (hgh serum)
  • Extensive (normal- expected serum concentration)
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14
Q

Phase 2 reactions

A

Conjugation reaction make more hydrophilic/ generally larger molecular weight

  • aids elimination via kidneys
  • Results in non-toxic inactive metabolite
  • glucuronidation- Most common (adds Glucose-like molecule)
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15
Q

CYP Terminology

A
  • Substrate: Drug/molecule that gets metabolized
  • Inducer: Drug/molecule that increases synthesis of CYP isozymes
  • Autoinducer: Drug increases synthesis of isozymes for which it is a substrate
  • Inhibitor: Reduces activity or competes for isozyme

(cause enzymes to be less active)

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16
Q

CYP450 metabolism

A
  • Metabolism-Chemical reaction
  • Enzyme facilitates chemical conversion of substrate (drug) to metabolite product
  • Chemical reaction favors substrate or metabolite depending on induction/inhibition of enzyme
17
Q

CYP450 Enzyme Induction

A
  • When enzyme inducer present activity of enzyme increased- pushes reaction to the right
  • Increased serum metabolite concentration/decreased the drug concentration
18
Q

CYP450 enzyme inhibition

A
  • Activity of enzyme is decreased pushes reaction to the left
  • Increased serum drug concentration/slows drug becoming metabolites
19
Q

Example

A
  • Drug A substrate of CYP3A4
  • Drug B is inducer of 3A4
  • If drug B added to drug regimen what happens to serum concentration of drug A?
  • Serum Concentration of A would decrease
  • Metabolite A would increase
20
Q

Elimination

A

Organs involved in elimination:

  • KIDNEY, liver, bile
  • Renal issues affect the drugs we can give to patients

Renal Elimination:

  • Glomerular filtration (Protein do not get passed, Passive free drug only, move from capillary to glomerular space)
  • Proximal tubular secretion (active transport)
  • Distal tubular reabsorption (drug may diffuse back into systemic circulation)
21
Q

Pediatrics: absorption

A

Oral route

-neonates: decreased gastric acid/ gastric emptying

rectal route

-useful, similar to adults

Topical/skin

  • infants have larger skin surface area
  • absorption significantly increased
  • inflammation, occlusion, heat increases absorption

Parenteral

  • IM (given lateral thigh due to low muscle mass in delt/ glute)
  • neonates: IV preferable to IM
22
Q

Pediatrics: metabolism

A

Highly variable and depends on:

  • Drugs mother was on during pregnancy
  • Agent patient
  • Some enzymes produced earlier than others
  • During first few weeks/months metabolic rate lower will need lower doses
  • During toddler/early childhood metabolic rate higher- dose may need to be higher
23
Q

Pediatrics: Drug sensitivity

A

Organ immaturity (Greater risk of toxicities)

-CNS develop slowly ( increased permeability of BBB)

Temperature regulation unstable

-toxic doses of tylenol/ asprin raise body temp

Skin more sensitive (allergic, ^ SA, ^ permeability, temp regulation)

  • Immediate onset ( urticaria, angioedema, anaphylaxis)
  • Delayed onset( erythema multiforme, fixed drug eruption)
24
Q

Half- life (t1/2)

A

-Time to change amount of drug in body by 1/2

25
Q

steady state concentration (Css)

A

What is Css?

-Concentration in the blood of the drug from in to out

What determines the Css?

-Amount of drug given

What determines how long to CSss?

-t1/2

How long does it take to reach Css?

-4-5 half-lifes

26
Q

General concepts

A

Dosing options

  • continous infusion (IV)
  • effect continuosly/ stop whenever
  • infection risk/ vasculitis/ inflamm response

Interval (scheduled dosing)

27
Q

Dosing Intervals

A
28
Q

Loading dose

A

When need to obtain rapid plasma level

-Initial doses of antibiotics/ Drugs that have relatively long half-life

Followed by maintenance doses to maintain steady-state

29
Q

Dose Adjustment

A
30
Q
A

Pharm (4 decks)

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