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18 Cards in this Set
- Front
- Back
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What does the partitiion coefficient describe?
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Lipid solubility of a drug
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A high partition coefficient translates into what?
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More lipid soluble...drug can cross membranes more easily...drug is better absorbed
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Drug absorption depends on 2 factors. What are they?
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Degree of ionization & lipid solubility
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If lipid solubility is quanitifed by partition coeff, what quantifies "degree of ionization"?
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pKa of the drug and the pH of the drug's environment
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Name 3 main mechanisms of drug movement across barriers.
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1. passive diffusion
2. special carriers 3. endo & exocytosis |
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What is the Henderson-Hasselbalch eqn good for?
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Tells us the % of drug that is ionized or non-ionized
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Does a higher % of non-ionized drug translate into better or worse absorption?
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a higher % of non-ionization means the drug is better absorbed
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How would explain a difference in absorption between 2 acidic drugs if they both have similar pKa values?
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If Drug A and Drug B have similar pKa values and are in the same pH environment, but Drug B absorbs better, Drug B is more lipid soluble and has a higher partition coefficient.
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Describe first pass effect.
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If a drug is given orally, it may become inactive before ever reaching the systemic circulation due to metabolism by the liver.
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What does pKa mean?
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pKa is the pH at which a drug is 50% ionized.
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Name the 5 main routes of drug administration
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1. Enteral
2. Parenteral 3. Pulmonary 4. Rectal 5. Topical |
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If a basic drug with a pKa of 5 is at a pH of 5, how would the % ionized change if the drug is moved to a pH of 4? pH of 6?
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At pH =5, this basic drug is 50% ionized. If the drug is put in a pH = 4, most of the drug will be ionized. In contrast, if the basic drug (pKa = 5) is put in a pH=6, most of the drug will be non-ionized.
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List 4 limitations of the oral route of drug administration.
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1. surface area
2. pH 3. particle size 4. lipid solubility |
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List 4 limitations of the parenteral route of drug administration.
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1. anaphylactic rxns
2. embolism 3. infection 4. hemolysis or blood agglutination |
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List 4 limitations of intramuscular route of drug administration.
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1. blood flow
2. drug ionization 3. lipid solubility 4. molecular size |
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List a limitation of pulmonary route of drug administration.
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Particles larger than 2microns probably not absorbed.
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What is the safest route of drug administration for a drug with a narrow therapeutic index?
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IV infusion
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Does intramuscular absorption rate follow zero order kinetics OR first order kinects?
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first order kinetics
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