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101 Cards in this Set
- Front
- Back
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Partition coefficient = ?
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Lipid/water solubility
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Aqueous solubility of a drug is _____ to its charge
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proportional
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Lipid solubility is _______ to its charge
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inversely proportional
*the more charged = the less lipid soluble |
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Compounds unionized, uncharged or nonpolar at physiolocial pH's
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Neutral
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What environment are neutral compounds usually more soluble in?
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lipid environments
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What are 2 examples of Neutral Compounds?
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Halothane
Hydrocortisone |
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Example of drugs that are always ionized, charged, or polar at physiological pH's
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Quaternary AmmonIUM compounds
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In what environment are permanently charged compounds usually more soluble?
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Aqueous environments
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Compounds that give up a proton in their unionized form
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Weak organic acids
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In what environment do weak organic acids pass membranes?
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Acidic b/c they will be in their unionized form
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In what environment could a weak organic acid become trapped?
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Alkaline environment
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Compounds that accept a proton in their unionized form
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Weak organic bases
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In what environment could a Weak organic base become trapped?
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Acidic environment
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What environment allows a Weak Organic Base to pass membranes?
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Alkaline environment
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What does pH = pKa mean?
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50% ionized and 50% unionized
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What pKa is more acidic: lower or higher?
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Lower
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What form predominates when pH < pKa?
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Acid form
**Weak organic acid will be uncharged **Weak organic base will be charged |
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What form predominates when pH > pKa?
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Base form
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log 0 = ?
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1
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antilog 1 = ?
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10
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antilog 2 = ?
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100
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How do you calculate ratio of Ionized vs. Unionized forms?
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1. [pKa - pH] = difference
2. Antilog of difference |
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Passage of drug molecules across biological membranes = ?
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Drug Permeation
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Describe "Aqueous Diffusion or Filtration"
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Drugs permeate membranes via the aqueous channels within central pores of specific proteins
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Capillaries in which part of the body lack pores with aqueous channels
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Brain
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5 parts of the brain with an open Blood-brain barrier
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Pituitary gland
Pineal gland Medium eminence Area postrema Choroid plexus |
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The largest pores involved in aqeuous diffusion exist where?
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Endothelial cells of the Kidney Glomeruli
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Most common route of Drug Permeation
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Lipid or Passive diffusion
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What is the force behind Lipid Diffusion?
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Concentration gradient
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In what environment do organic acids best pass lipid membranes?
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Acidic
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In what environment do organic bases best pass lipid membranes?
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Basic environments
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Why does Active Transport have limited capacity?
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Saturation of carrier molecules
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Where are 4 sites of Active Transport of drugs?
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Neuronal membranes
Choroid Plexus Renal Tubular cells Hepatocytes |
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List 5 characteristics of Active Transport
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1. structure selectivity
2. competition by congeners 3. energy requirement 4. easily saturated 5. movement against a concentration gradient |
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Carrier-mediated process not requiring energy
Movement of chemical CANNOT occur against a concentration or electrochemical gradient |
Facilitated diffusion
*can be saturated |
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List 4 examples of compounds that participate in facilitated diffusion
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Sugars
Amino acids Purines Pyrimidines |
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These function in the movement of molecules into or out of tissues
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Transporters
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When cells engulf extracellular material within membrane vesicles
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Pinocytosis = endocytosis
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What Molecular weight can cells perform pinocytosis?
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over MW 1000
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Pinocytosis is only important for which few chemicals?
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Proteins -> Botulinum toxin
Protein Complexes -B12 with Intrinsic Factor -Iron with Transferrin |
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Define Pharmacokinetics
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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 |
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What are the 2 important aspects of Pharmacokinetics?
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Rate
Extent |
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Why are drugs that are administered in aqueous solution absorbed more rapidly than those given in oily solution, suspension or solid form?
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because they mix more readily with the aqueous phase at the absorptive site
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What 2 things is Dissolution rate dependent on?
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Formulation itself and the patient
*there is variation among patients and products formulated by different manufacturers |
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T or F: Dilute concentrations absorb more readily than high concentrations of drug
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False
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T or F: the rate of absorption from a subcutaneous site is usually lower than from an Intramuscular site
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True
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Why is the rate of Absorption from a subcutaneous site usually lower than from an Intramuscular site?
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b/c blood from to subcutaneous tissue is usually lower than flow to muscle
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What explains for the fact that drugs are absorbed better from the small intestine than the stomach?
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Larger surface area
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Environment that is favorable to absorption of Weak Acids
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Acidic environment
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Environment that is favorable to ABSORPTION of Weak Bases
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Basic environment
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T or F: the shorter amount of time a drug remains in contact with the membranes, the greater amount absorbed
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False
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Part of GI where drugs stay in contact for a longer period of time
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Small Intestine = greater absorption
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Most common route of drug administration
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ORAL
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Oral administration has poor absorption of these types of molecules
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Large and Charged
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2 things that can destroy a drug given orally
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Enzymes (peptides and proteins)
Low pH (penicillin, cephalosporins) |
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2 drugs that if given orally will bind or complex with GI contents
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Tetracycline with Calcium
Fluoroquinolines with Calcium |
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T or F: Most drugs are absorbed more readily when given on a full stomach
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False: absorbed more readily on empty stomach
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Important!!!
3 drugs with a high First-Pass Effect |
1. Morphine
2. Nitroglycerin 3. Lidocaine |
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Explain "First-Pass" Metabolism
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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 |
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5 things that slow down gastric emptying
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1. fats
2. low pH 3. Bulk 4. Anticholinergics 5. Hypothyroidism |
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5 things that speed up gastric emptying
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1. Fasting
2. Hunger 3. high pH 4. Anxiety 5. Hyperthyroidism |
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Why do drugs that slow gastric emptying delay absorption?
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b/c the drug resides for a longer time in the poor absorptive environment of the stomach before they reach the intestine
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What is the most direct route of drug administration?
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Intravenous = bypasses the absorption barriers
*100% Bioavailability |
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Drug administration that is easiest to titrate
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Intravenous
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2 Drug characteristics that make them suitable for IV administration
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1. Large volumes
2. Irritating substances |
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2 drugs characteristics that make them not suitable for IV administration
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Oily substances
Suspensions |
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Intramuscular method used to provide a slowly absorbed reservoir of drug
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Depot injection of drugs in oil
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Administration suitable for implantation of some solid pellets
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Subcutaneous
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Example of drug injected subcutaneously as solid pellet
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Norplant: progestin implant for long term contraception
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Administration route used for Volatile compounds
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Inhalation
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2 volatile compounds that are given via inhalation
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Halothane
Amyl Nitrite |
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2 properties of the lungs that allows for rapid absorption via inhalation of drug
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1. large surface area of alveolar membranes
2. high blood flow thru lungs |
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7 drugs given by topical route (patches)
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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 |
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When is the Rectal route of administration useful?
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when oral ingestion is precluded b/c of vomiting or when the patient is unconscious
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2 groups of patients in which the rectal route is often used
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Small children
Geriatric patients if they can't swallow well |
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Drug often given by Rectal route due to seizures
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Diazepam
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The compartment where a drug appears to distribute = ?
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Apparent Volume of Distribution (Vd)
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How is the Apparent Volume of Distribution calculated?
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Vd = amount of drug (iv) / Co
*Co = extrapolated conc. of drug in plasma at time 0 after equilibration |
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Total body water = ___% of body weight
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60%
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Explain the distribution of fluids in each compartment
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Intracellular = 2/3
Extracellular = 1/3 -Plasma = 1/4 of EC -Interstitial = 3/4 of EC |
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Types of drugs found in Plasma water
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1. Strongly plasma-protein bound drugs
2. Large drugs |
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Example of drug found in plasma water
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Heparin = an anticoagulant
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Type of drug found in Extracellular water and give an example
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Large water-soluble drugs
Mannitol = osmotic diuretic |
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Type of drug found in total body water and give specific example
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Small water-soluble drugs
Ethanol |
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Example of a drug that avidly binds to tissue
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Chloroquine = anti-malarial drug
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Example of a drug that is stored in FAT
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Thiopental = barbiturate general anesthetic
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Drug that is deposited in Calcium-rich regions (=bone and teeth) and is not administered to children with developing teeth
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Tetracyclines
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3 drugs that accumulate in bone
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Tetracyclines
Lead Fluoride |
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3 properties of drugs that have a high plasma protein binding
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1. have a low Vd (b/c they are in the plasma)
2. high plasma conc. 3. often prolonged half-life |
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What serves as a transcellular reservoir for drugs slowly absorbed or undergoing enterohepatic circulation?
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GI tract
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Term for when pH gradient influences the distribution of weak organic acids and bases
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Ion-trapping
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Plasma protein binding drugs have a high or low Volume of distribution?
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Low
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Tissue binding drugs have a high or low volume of distribution?
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high
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Which is absorbed faster: Intramuscular or Subcutaneous? Why?
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Intramuscular due to higher blood flow
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What is one advantage of administering via the Rectal route?
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Drug does NOT pass through the Liver before entering the Systemic circulation
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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 |
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What is the consequence if certain drugs tend to distribute into reservoirs, such as fat
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Decreases plasma levels
Prolongs half-lives |
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Which is absorbed faster: Intramuscular or Subcutaneous? Why?
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Intramuscular due to higher blood flow
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What is one advantage of administering via the Rectal route?
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Drug does NOT pass through the Liver before entering the Systemic circulation
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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 |
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What is the consequence if certain drugs tend to distribute into reservoirs, such as fat
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Decreases plasma levels
Prolongs half-lives |
