Drug effects on elimination and clearance
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What are the two drug types?
Water soluble and lipid soluble
What is drug action?
- drug must get access to sites of action
- Drugs tend to bind to tissues, usually protein
- drug alter the action of enzymes, ion channels and receptors
What do drugs do to receptors?
Drugs activate or block the receptor, activation of the receptor activates a cell signal
What are the law of mass action that applies to drug receptor interaction?
- Pharmacological effects are reversible because the drug receptor complex is reversible
- Pharmacological effects are proportional to the number receptors occupied
- Pharmacological effect plataeu because they are limited by the total number of receptors
- Drug effects are proportional to the dose!!!
measure amount of drug required for effect
maximum effect obtained with drug
reproducibility of data
What is the main determinant in the decline in GFR?
What drug are eliminated directly by the kids?
- Water soluble
- involves no chemical change to the drug
What drugs are readily reabsorbed?
highly lipid soluble
How do you assess kid fxn?
serum creatine reflects GFR
How does age affect renal fxn?
THere is a steady and proportional decline in the average GFR with increase of age
What are the two mechanism how drugs are handled by kids?
- active tubular secretion
- passive diffusion, depends on ionization at certain pHs
What should we know about gentamycin?
- ONce a day dosing, with kid failure dosing increases past once daily
- toxicity relates to trough concentrations
What should we know about digoxin?
IN the presence of renal failure must increase the dosing frequency
What are the results of drug concentations with renal failure?
Accumulation of drug in the body can lead to toxicity
What is first pass metabolism?
Following non-parental dosage form a significant portion of the dose may be metabolically inactivated in the intestinal endothelium or the liver before it reaches systemic circulation
What is the role of metabolism?
- Metabolites are less active
- metabolites are more water soluble and more polar
- Prodrugs that require metabolism to be active as active metabolites
- Metabolites are more toxic
What is the phase I reactions of metabolism?
Convert the parent drug into a more polar metabolite introducing or unmasking a functional group, metabolites are usually inactive
WHat is phase II reaction of metabolism?
Conjugate an endogenous substrate to a funcational gorup on the drug or phase I metabolite
What happens to pharmacokinetic properties as people age?
- Acetylation and conjugation do not change
- Oxidative metabolism by CYP decreases with age resulting in a decreased clearance of drugs
WHat does hepatocellular disease do to the liver?
Decreases liver perfusion
WHat are the indicators of liver disease?
Establishe cirrhosis, splenomegaly, jaundice, increased prothrombin time
How can cardiac failure affect the liver?
Decreas liver perfusion
What are some pharmcodynamic consideration of liver disease?
Tissues may be excessively sensitive to low concentrations of the drug ex: morphine  in the brain in the presence of liver failure
What does the liver fxn test consist of?
- Alkaline phosphatase
- Other liver labs
Why is transaminase part of the LFT?
because it is released after liver heaptocellular injury
What are the two forms of transaminases?
- Aspartate aminotransaminase
- Alanine aminotransaminase: more specific in myopathies
elevated transaminases indicate:
- acute toxic injusty apap ischemia
- acute viral disease
- alcohol heapatitis
What does an elevated AST:ALT
elevated in alcolic disease
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