Flashcards in 9.7 Pharmacology 5 Deck (32):
extent to which drug reaches systemic circulation
What does bioavailability depend on?
- route of administration
- drug's ability to cross membrane barriers
- passive diffusion
- active transport
- facilitated diffusion
Why does ionization state affect absorption?
pH of digestive system interacts with the drug
- how quickly and easily it is to get rid of the drug
volume of distribution
people who weight more require larger amts of the medicine for it to work
factors affecting distribution of drugs in the body
- tissue permeability
- blood flow
- binding to plasma proteins
- binding to subcellular components
- volume of distribution
major tissue permeability concern
blood brain barrier
blood flow and distribution of drugs in the body
- drugs have higher access to well-perfused areas
- why foot wounds don't heal unless peripheral blood flow is adequate
Which drugs can reach a target to create a pharmacologic effect?
only unbound or "free" drugs
- drug remains bound to a protein and is sequestered in the vascular system
- doesn't produce a therapeutic response
binding to subcellular components
- drug is "trapped" by organelles within a cell
- can't be distributed to other target areas
example of subcellular binding
certain antidepressants and antipsychotics with relatively high pH are attracted to the acidic lysosome
volume of distribution: important considerations
- may be possible to increase dosage to achieve therapeutic effect
- only if TI permits
What tissues might drugs be stored in that could have adverse effects?
- adipose tissue
most common site for drug storage - why?
- adipose tissue
- most drugs are lipid-soluble
How long do drugs stay in adipose tissue and why?
tends to stay a long time
- low metabolic rate
- poor blood perfusion
What can concentrate heavily in adipose tissue?
- anesthetics (barbiturates)
- inhaled anesthetics (halothane)
bone and drugs
- some drugs can bind to skeletal matrix
What is a toxic substance that can bind to bone?
How do drugs get stored in muscle?
example of drug that gets stored in muscle
most common organs for drug storage
What drugs are commonly stored in the liver and kidneys?
Problems with drug storage in tissue
- can damage, even in therapeutic doses
- can prevent medicine from reaching target tissue
- can redistribute the drug unpredictably
What are ways that are used to combat drug storage problems?
- controlled-release preparations
- targeting drug to specific cell or tissue
benefit to controlled-release preparations
- prevents large fluctuations in plasma
- sustained levels
controlled-release preps are useful for these types of meds
- cardiovascular (beta and calcium channel blockers)
- anti-Parkinson drugs
How do implanted drugs work?
- small, measured dose on a programmed schedule into a specific body part
- epidural or subarachnoid
examples of implanted drugs
- spasticity: baclofen or lioresal
- insulin pump into fatty tissue
How can a drug be targeted to specific cells or tissues?
- use of a "prodrug" or inactive form
- converts to active form when specific enzymes or biochemical properties of the target tissue recognize it