Unit 1. Lec 1: Pharmacokinectics Flashcards by Moronfoluwa Olajide

Define Pharmacokinetics

Study of absorption, distrubition and elimination of drugs and other substances

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What is the affect of drugs on illnesses?

They do not cure the illness, they just mask the symptoms

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True or False: All drugs at high enough concentrations are poisonous

True

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What determines the poisonious level of a drug/substance?

Dosage

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Absorption

The process by which the drugs enter the systemic circulation

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What is the only way to bypass absorption

Through IV

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What other ways can drugs enter systemic circulation?

Oral–>GI system–>systemic blood
Skin (super lipophilic)–>systemic blood
Inhalent (Lungs)–>systemic blood

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True of False: Drugs taken by the hepatic vein are absorbed

Provide explanation

False; b/c they have not entered the systemic circulation

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Distribution

The phenomenon by which drugs reach its site of action. (To target receptor)

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Elimination

The process by which the drugs are enzymatically altered (biotransformation) mainly in the liver and eventually excreted by the kidneys.

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What must occur for the absorption, distribution and elimination of drugs?

The drug must cross the cell membrane

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How well a drug can cross the cell membrane is correlated with?

their physiological characteristics

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List the factors that determine the transfer of drugs across membranes

Molecular size and shape of drug
Solubility of drug (lipid:water partition coefficient)
Most drugs are weak acids or weak bases

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What types of drugs can cross the blood brain barrier (BBB)?

Highly lipid soluble

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What types of drugs cannot cross the BBB?

Water soluble

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What is the lipid:water partition coefficient explaining?

How lipid soluble a drug is

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Weak acids…..
Weak bases…..

Weak acids give H+ ion
Weak bases take H+ ion

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Nonionized drugs ____ cross the cell membrane. Ionized drugs ____ cross

can, cannot

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What is a nonionized vs ionized ion?

Nonionized=no charge
Ionized=charged

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You add 1 g of a drug, 1 g of water and 1 g of oil in a separatory funnel and mix it. You remove the water and measure 0.1 g of the drug in the water and 0.9 g of the drug in the oil. What is the lipid:partition coefficient?

0.9/0.1 or 9 making the drug lipophilic

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The degree of ionization depends on what?

What is pka

50% of ionization; pH=pka

When the pH is low (more acidic), weak acid is

More unionized

When the pH is high (more basic) ,weak acids are

More ionized

When the pH is low (more acidic), weak bases are

more ionized

When the pH is high (more basic), the weak bases are

more unionized

What is the Henderson-Hasselbalch Equation

Allows for the calculation of the degree of ionzation for weak acids or weak bases

What is the Henderson Hasselbalch equation for a weak acid | I owe U

pH=pka +log10(I/U) | I=ionized U=unionized

What is the Henderson Hasselbalch equation for weak bases | U are Basic, U over I

pH=pka+log10(U/I) | I=Ionized U=Unionized

List pH of selected body fluids

* Gastric juice:1.0-3.0 * Small intestine (duodenum): 5.0-6.0 * Small intestine (ileum): 8.0 * Large Intestine: 8.0 * Plasma: 7.4 * Cerebrospinal fluid: 7.3 * Urine: 4.0-8.0

Term for when drugs become trapped on one side of a lipid mucosal barrier due to change of pH

Ion trapping

Weak acids get trapped on what side?

Basic

List the processes (5) of drug transfer

* Passive Diffusion * Active Transport (Carrier-mediated process) * Facilitated Diffusion ( Carrier-mediated process) * Bulk Flow * Pinocytosis

What is the most common form of drug transfer?

Passive diffusion

Passive diffusion: 1. movement on gradient? 2. saturable? 3. carrier mediated? 4. example

1. Moves only DOWN the [ ] gradient 2. NOT saturable 3. NOT carrier-mediated 4. ethanol (alcohol)

Active transport: 1. movement on gradient? 2. saturable? 3. carrier mediated? 4. Energy? 5. examples

1. Can move up and down [ ] gradient 2. Can be saturated (limited carrier proteins) 3. Requires a carrier 4. Needs ATP 5. Pencilin in kindneys, p-gylcoprotein, and MRP

What are xenobiotics?

Foreign chemical substance that goes through active transport

Faciliated diffusion: 1. movement on gradient? 2. saturable? 3. carrier mediated? 4. example

1. Moves only DOWN the [ ] gradient 2. Can be saturated 3. Involves a carrier (no energy needed) 4. amino acids transport into the brain

What does fixed capacity mean?

You reach vmax so you cant go higher than that

Describe bulk flow

* Movement of free molecules through the capillary junctions ## Footnote Only free drugs can move through the fenestrations (holes) b/n capillaries, but most drugs are bound to plasma proteins (Not with BBB)

Describe Pinocytosis

Formation and movement of vesicles ## Footnote Plays a minor role in drug transport

List the factors (5) that influence drug absorption

1. Solubility 2. Concentration 3. Circulation 4. Surface area 5. Time

How does Solubility affect drug absorption?

* Aqueous vs oily solution * Higher Lipid H2O coeffient means drugs absorb better * pH (ex. aspirin coat)

How does concentration affect drug absorption

High [ ] of drug absorbs more rapidly

How does circulation affect drug absorption?

* Higher circulation, Higher absorption (e.g. local massage, heat application) * Lower circulation, Lower absorption (e.g. state of shock, disease state)

How does surface area affect drug absorption?

* Increase surface area, increase absorption * e.g. Intestinal muscosa (oral meds), pulmonary alveolar epithelium (gases like anesthia), skin (patches, pesticides)

How does time affect drug absorption?

* Shorter time (present of drug), faster absorption * Longer time (presence of drug), slower absorption

Which of the following bypasses absorption? a. PO b. Topically c. Intravenous d. Inhalation

c. Intravenous ## Footnote PO-->Goes through first pass effect

2. Which of the following processes has the potential issue of becoming saturated? a. Passive transport b. Active transport c. Facilitated diffusion d. B and C

d. B and C ## Footnote Facilited diffusion has NO transporters

3. Which of the following is the correct equation for calculating the degree of ionization of a week base? a. pH = pKa + log U/I b. pH = pKa + log I/U c. pKa = pH + log U/I d. pKa = pH + log I/U

a. pH=pKa+logU/I ## Footnote b. pH=pKa + logI/U (Weak Acid)

6. Which of the following is not an influence on drug absorption? a. Bulk Flow b. Solubility c. Concentration d. Circulation

a. Bulk Flow (process of drug transfer)