Lecture 1 - Part 2 Flashcards
What is pharmacokinetics (PK)?
- what the body does to the drug
- absorption, digestion, metabolism, excretion (ADME)
What is pharmacodynamics (PD)?
- what the drug does to the body
- MOA (mechanism or action)
- dose response (efficacy, potency, therapeutic index)
- effects
- side effects (SEs) aka Adverse Drug Reaction (ADRs)
What are the two ways drugs can be absorbed?
1) passive diffusion: water and water-soluble substances and small lipids move with a concentration gradient
2) active transport : minerals, some sugars, and most amino acids move against a concentration gradient with an input of energy
Define bioavailability
- the extent to which the drug reaches the systemic circulation
- the percentage of the drug administered that reaches the bloodstream
what does bioavailability depend on?
1) route of administration
2) drug’s ability to cross membrane barriers
- active, passive, facilitated, special processes
What does drug distribution mean?
after absorption, where the drug goes based on tissue permeability, blood flow, plasma proteins, and subcellular components
Where are drugs stored?
1) adipose
2) bone
3) muscle
4) organs
What is volume of distribution (Vd)
a ratio that expresses the amount of drug administered/concentration of drug in plasma
what factors affect distribution?
1) tissue permeability
2) blood flow
3) binding to plasma proteins
4)binding to subcellular components
What organ takes part in drug excretion?
kidneys (nephron)
Define clearance of drugs
the ability of all organs and tissues to eliminate the drug or the ability of a single organ or tissue to eliminate the drug
what is a drug’s half life?
amount of time required for 50% of the drug remaining in the body to be eliminated
What factors can cause variations in response to drugs?
1) genetics
2) disease (esp liver or kidneys)
3) age
4) diet
5) gender
6) drug interactions
7) environmental
8) cigarettes/alcohol
9) obseity
10) exercise
11) injuries
Drug absorption in infants
- less acidic stomach –> increases bioavailability of acid labile drugs -PCN
- delayed gastric emptying –> increases time to reach therapeutic concentrations
- larger relative skin surface area –> increases cutaneous perfusion
- thinner stratum corneum –> increases absorption (topicals)
Drug distribution in infants
- body water
- preterm: 85%; term: 75%; 5 months: 60% (adult level)
- adipose tissue (baby fat 15%)
- serum albumin binding decreased: ~90-92% (98% adult)
metabolism in infants
- hepatic enzyme activity 50-70% of adult, but reach adult levels in 1st year
excretion in infants
- glomerular filtration and tubular secretion decreased
- reach adult levels ~ 5-7 months (in first 7 months, need to worry about adverse reactions from drugs dependent upon the kidney for elimination
absorption in the elderly
- increased gastric pH vs adult (much more versus infant)
- delayed gastric emptying (increases time to reach therapeutic concentrations)
distribution in the elderly
- body water: decreased TBW to 53% of adult
- increased adipose tissue (more body fat)
- decreased serum albumin binding: ~95% (98% in 40-50 year old adult)
metabolism in the elderly
1) little change in liver function tests, however there is some decrease in hepatic biotransformation
excretion in the elderly
- decreased glomerular filtration and tubular secretion (this is the cause of most adverse drug reaction sin the elderly)
what influences what the drug does to the body?
- depends on the drug receptors and the ability of the drug to bind to those receptors
What is a dose-response curve?
- provides information about the dosage range over which the drug is effective
- provides information about peak response
What is E50
- the median effective dose
- dose at which 50% of the population responds to the drug in a specific manner
