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101 Cards in this Set

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Partition coefficient = ?
Lipid/water solubility
Aqueous solubility of a drug is _____ to its charge
proportional
Lipid solubility is _______ to its charge
inversely proportional

*the more charged = the less lipid soluble
Compounds unionized, uncharged or nonpolar at physiolocial pH's
Neutral
What environment are neutral compounds usually more soluble in?
lipid environments
What are 2 examples of Neutral Compounds?
Halothane

Hydrocortisone
Example of drugs that are always ionized, charged, or polar at physiological pH's
Quaternary AmmonIUM compounds
In what environment are permanently charged compounds usually more soluble?
Aqueous environments
Compounds that give up a proton in their unionized form
Weak organic acids
In what environment do weak organic acids pass membranes?
Acidic b/c they will be in their unionized form
In what environment could a weak organic acid become trapped?
Alkaline environment
Compounds that accept a proton in their unionized form
Weak organic bases
In what environment could a Weak organic base become trapped?
Acidic environment
What environment allows a Weak Organic Base to pass membranes?
Alkaline environment
What does pH = pKa mean?
50% ionized and 50% unionized
What pKa is more acidic: lower or higher?
Lower
What form predominates when pH < pKa?
Acid form

**Weak organic acid will be uncharged
**Weak organic base will be charged
What form predominates when pH > pKa?
Base form
log 0 = ?
1
antilog 1 = ?
10
antilog 2 = ?
100
How do you calculate ratio of Ionized vs. Unionized forms?
1. [pKa - pH] = difference

2. Antilog of difference
Passage of drug molecules across biological membranes = ?
Drug Permeation
Describe "Aqueous Diffusion or Filtration"
Drugs permeate membranes via the aqueous channels within central pores of specific proteins
Capillaries in which part of the body lack pores with aqueous channels
Brain
5 parts of the brain with an open Blood-brain barrier
Pituitary gland
Pineal gland
Medium eminence
Area postrema
Choroid plexus
The largest pores involved in aqeuous diffusion exist where?
Endothelial cells of the Kidney Glomeruli
Most common route of Drug Permeation
Lipid or Passive diffusion
What is the force behind Lipid Diffusion?
Concentration gradient
In what environment do organic acids best pass lipid membranes?
Acidic
In what environment do organic bases best pass lipid membranes?
Basic environments
Why does Active Transport have limited capacity?
Saturation of carrier molecules
Where are 4 sites of Active Transport of drugs?
Neuronal membranes

Choroid Plexus

Renal Tubular cells

Hepatocytes
List 5 characteristics of Active Transport
1. structure selectivity
2. competition by congeners
3. energy requirement
4. easily saturated
5. movement against a concentration gradient
Carrier-mediated process not requiring energy

Movement of chemical CANNOT occur against a concentration or electrochemical gradient
Facilitated diffusion

*can be saturated
List 4 examples of compounds that participate in facilitated diffusion
Sugars
Amino acids
Purines
Pyrimidines
These function in the movement of molecules into or out of tissues
Transporters
When cells engulf extracellular material within membrane vesicles
Pinocytosis = endocytosis
What Molecular weight can cells perform pinocytosis?
over MW 1000
Pinocytosis is only important for which few chemicals?
Proteins -> Botulinum toxin

Protein Complexes
-B12 with Intrinsic Factor
-Iron with Transferrin
Define Pharmacokinetics
Deals with the time course of the fate of a drug in the body and the relationship of these processes to the intensity and duration of clinical responses

*Absorption, Distribution, Metabolism, and Excretion of a drug
What are the 2 important aspects of Pharmacokinetics?
Rate

Extent
Why are drugs that are administered in aqueous solution absorbed more rapidly than those given in oily solution, suspension or solid form?
because they mix more readily with the aqueous phase at the absorptive site
What 2 things is Dissolution rate dependent on?
Formulation itself and the patient

*there is variation among patients and products formulated by different manufacturers
T or F: Dilute concentrations absorb more readily than high concentrations of drug
False
T or F: the rate of absorption from a subcutaneous site is usually lower than from an Intramuscular site
True
Why is the rate of Absorption from a subcutaneous site usually lower than from an Intramuscular site?
b/c blood from to subcutaneous tissue is usually lower than flow to muscle
What explains for the fact that drugs are absorbed better from the small intestine than the stomach?
Larger surface area
Environment that is favorable to absorption of Weak Acids
Acidic environment
Environment that is favorable to ABSORPTION of Weak Bases
Basic environment
T or F: the shorter amount of time a drug remains in contact with the membranes, the greater amount absorbed
False
Part of GI where drugs stay in contact for a longer period of time
Small Intestine = greater absorption
Most common route of drug administration
ORAL
Oral administration has poor absorption of these types of molecules
Large and Charged
2 things that can destroy a drug given orally
Enzymes (peptides and proteins)

Low pH (penicillin, cephalosporins)
2 drugs that if given orally will bind or complex with GI contents
Tetracycline with Calcium

Fluoroquinolines with Calcium
T or F: Most drugs are absorbed more readily when given on a full stomach
False: absorbed more readily on empty stomach
Important!!!

3 drugs with a high First-Pass Effect
1. Morphine

2. Nitroglycerin

3. Lidocaine
Explain "First-Pass" Metabolism
some drugs are metabolized by enzymes in the intestinal flora, intestinal mucosa or liver before gaining access to the general circulation

Presystemic metabolism can siginificantly decrease systemic availability
5 things that slow down gastric emptying
1. fats
2. low pH
3. Bulk
4. Anticholinergics
5. Hypothyroidism
5 things that speed up gastric emptying
1. Fasting
2. Hunger
3. high pH
4. Anxiety
5. Hyperthyroidism
Why do drugs that slow gastric emptying delay absorption?
b/c the drug resides for a longer time in the poor absorptive environment of the stomach before they reach the intestine
What is the most direct route of drug administration?
Intravenous = bypasses the absorption barriers

*100% Bioavailability
Drug administration that is easiest to titrate
Intravenous
2 Drug characteristics that make them suitable for IV administration
1. Large volumes

2. Irritating substances
2 drugs characteristics that make them not suitable for IV administration
Oily substances

Suspensions
Intramuscular method used to provide a slowly absorbed reservoir of drug
Depot injection of drugs in oil
Administration suitable for implantation of some solid pellets
Subcutaneous
Example of drug injected subcutaneously as solid pellet
Norplant: progestin implant for long term contraception
Administration route used for Volatile compounds
Inhalation
2 volatile compounds that are given via inhalation
Halothane

Amyl Nitrite
2 properties of the lungs that allows for rapid absorption via inhalation of drug
1. large surface area of alveolar membranes

2. high blood flow thru lungs
7 drugs given by topical route (patches)
1. Nicotine
2. Estrogen
3. Testosterone
4. Fentanyl = opioid analgesic (pain releiver)
5. Scopolamine = anticholinergic
6. Clonidine = anti-hypertensive
7. Nitroglycerin = vasodilator

Smoking hermaphrodite clone vent's into a Scope looking for Dynamite; all while wearing a Patch
When is the Rectal route of administration useful?
when oral ingestion is precluded b/c of vomiting or when the patient is unconscious
2 groups of patients in which the rectal route is often used
Small children

Geriatric patients if they can't swallow well
Drug often given by Rectal route due to seizures
Diazepam
The compartment where a drug appears to distribute = ?
Apparent Volume of Distribution (Vd)
How is the Apparent Volume of Distribution calculated?
Vd = amount of drug (iv) / Co

*Co = extrapolated conc. of drug in plasma at time 0 after equilibration
Total body water = ___% of body weight
60%
Explain the distribution of fluids in each compartment
Intracellular = 2/3
Extracellular = 1/3
-Plasma = 1/4 of EC
-Interstitial = 3/4 of EC
Types of drugs found in Plasma water
1. Strongly plasma-protein bound drugs

2. Large drugs
Example of drug found in plasma water
Heparin = an anticoagulant
Type of drug found in Extracellular water and give an example
Large water-soluble drugs

Mannitol = osmotic diuretic
Type of drug found in total body water and give specific example
Small water-soluble drugs

Ethanol
Example of a drug that avidly binds to tissue
Chloroquine = anti-malarial drug
Example of a drug that is stored in FAT
Thiopental = barbiturate general anesthetic
Drug that is deposited in Calcium-rich regions (=bone and teeth) and is not administered to children with developing teeth
Tetracyclines
3 drugs that accumulate in bone
Tetracyclines

Lead

Fluoride
3 properties of drugs that have a high plasma protein binding
1. have a low Vd (b/c they are in the plasma)
2. high plasma conc.
3. often prolonged half-life
What serves as a transcellular reservoir for drugs slowly absorbed or undergoing enterohepatic circulation?
GI tract
Term for when pH gradient influences the distribution of weak organic acids and bases
Ion-trapping
Plasma protein binding drugs have a high or low Volume of distribution?
Low
Tissue binding drugs have a high or low volume of distribution?
high
Which is absorbed faster: Intramuscular or Subcutaneous? Why?
Intramuscular due to higher blood flow
What is one advantage of administering via the Rectal route?
Drug does NOT pass through the Liver before entering the Systemic circulation
Liters in a 70 kg man:
1. Plasma water
2. Extracellular water
3. Total body water
4. Tissue concentration
1. 3 L
2. 14 L
3. 42 L
4. >49 L
What is the consequence if certain drugs tend to distribute into reservoirs, such as fat
Decreases plasma levels

Prolongs half-lives
Which is absorbed faster: Intramuscular or Subcutaneous? Why?
Intramuscular due to higher blood flow
What is one advantage of administering via the Rectal route?
Drug does NOT pass through the Liver before entering the Systemic circulation
Liters in a 70 kg man:
1. Plasma water
2. Extracellular water
3. Total body water
4. Tissue concentration
1. 3 L
2. 14 L
3. 42 L
4. >49 L
What is the consequence if certain drugs tend to distribute into reservoirs, such as fat
Decreases plasma levels

Prolongs half-lives