Week 1 Chapter 1, 3, 4
1. Absorption: This is the process of moving a drug from the site of
administration into the bloodstream. Factors affecting absorption
include the drug's formulation rate and extent like rate of dissolution,
blood flow, surface area, PH partitioning, route of administration, and
interactions with other substances that may alter gastric motility.
2. Distribution: Once in the bloodstream, drugs are transported
throughout the body. Distribution can be influenced by blood flow,
capillary permeability, lipid solubility, the drug's ability to bind to
plasma proteins, and the presence of barriers like the blood-brain
barrier, placenta, receptor site affinity cause action (agonist), block
action (antagonist). And 3 ways to cross a cell membrane (channels
and pores, transport system P-glycoprotein, direct penetration).
3. Metabolism: This process changes the drug's activity, often making it
easier to excrete. Metabolism primarily occurs in the liver and can be
affected by age, liver function, and interactions with other drugs that
modify hepatic enzymes.
4. Excretion: The removal of drugs from the body, primarily through the
kidneys. Factors like renal function and drug interactions that alter
renal filtration rates can influence excretion.
Advantages and Disadvantages of Common Drug Administration
Routes
1. Enteral (Oral)
Advantages: Convenient, non-invasive, and generally safe.
Disadvantages: Slower absorption, affected by food and
digestive enzymes, and first-pass metabolism in the liver can
reduce drug efficacy.
2. Topical
Advantages: Direct application to the site of action, reduced
systemic effects.
Disadvantages: Limited to surface areas, potential for local
irritation.
3. Parenteral (Sq, IV, IM)
, Advantages: Rapid absorption bypasses the digestive system,
useful for patients unable to take oral medications.
Disadvantages: Invasive, risk of infection, requires professional
administration.
Effect of Altered Hepatorenal Function
Hepatic Function: Impaired liver function can lead to decreased
drug metabolism, increasing the risk of drug accumulation and
toxicity.
Renal Function: Kidney disease can slow drug excretion, prolonging
drug action and increasing toxicity risk. Monitoring for signs of
toxicity is crucial in patients with compromised renal function.
Effect of Altered Hepatorenal Function on Drug Effects and
Serum Drug Levels
Altered hepatorenal function can significantly impact drug
metabolism and excretion. When liver function is compromised, the
metabolism of drugs is reduced, leading to higher serum drug levels
and an increased risk of toxicity. Similarly, impaired kidney function
slows drug excretion, prolonging drug action and further increasing
toxicity risk. This necessitates careful monitoring and dosage
adjustments to prevent adverse effects.
Plasma Protein Binding
Drugs often bind to plasma proteins in the blood, which affects their
distribution. Only unbound drugs can exert therapeutic effects. If two
drugs compete for the same binding sites, one may displace the other,
increasing the concentration of the free drug and potentially leading
to toxicity. For example, diazepam can displace phenytoin, raising
phenytoin's free concentration and risk of adverse effects.
First Pass Effect
The first-pass effect refers to the initial metabolism of a drug in the
liver after oral administration, reducing its concentration before it
reaches systemic circulation. This can decrease the drug's efficacy,
requiring higher doses or alternative administration routes to achieve
the desired therapeutic effect.
1. Absorption: This is the process of moving a drug from the site of
administration into the bloodstream. Factors affecting absorption
include the drug's formulation rate and extent like rate of dissolution,
blood flow, surface area, PH partitioning, route of administration, and
interactions with other substances that may alter gastric motility.
2. Distribution: Once in the bloodstream, drugs are transported
throughout the body. Distribution can be influenced by blood flow,
capillary permeability, lipid solubility, the drug's ability to bind to
plasma proteins, and the presence of barriers like the blood-brain
barrier, placenta, receptor site affinity cause action (agonist), block
action (antagonist). And 3 ways to cross a cell membrane (channels
and pores, transport system P-glycoprotein, direct penetration).
3. Metabolism: This process changes the drug's activity, often making it
easier to excrete. Metabolism primarily occurs in the liver and can be
affected by age, liver function, and interactions with other drugs that
modify hepatic enzymes.
4. Excretion: The removal of drugs from the body, primarily through the
kidneys. Factors like renal function and drug interactions that alter
renal filtration rates can influence excretion.
Advantages and Disadvantages of Common Drug Administration
Routes
1. Enteral (Oral)
Advantages: Convenient, non-invasive, and generally safe.
Disadvantages: Slower absorption, affected by food and
digestive enzymes, and first-pass metabolism in the liver can
reduce drug efficacy.
2. Topical
Advantages: Direct application to the site of action, reduced
systemic effects.
Disadvantages: Limited to surface areas, potential for local
irritation.
3. Parenteral (Sq, IV, IM)
, Advantages: Rapid absorption bypasses the digestive system,
useful for patients unable to take oral medications.
Disadvantages: Invasive, risk of infection, requires professional
administration.
Effect of Altered Hepatorenal Function
Hepatic Function: Impaired liver function can lead to decreased
drug metabolism, increasing the risk of drug accumulation and
toxicity.
Renal Function: Kidney disease can slow drug excretion, prolonging
drug action and increasing toxicity risk. Monitoring for signs of
toxicity is crucial in patients with compromised renal function.
Effect of Altered Hepatorenal Function on Drug Effects and
Serum Drug Levels
Altered hepatorenal function can significantly impact drug
metabolism and excretion. When liver function is compromised, the
metabolism of drugs is reduced, leading to higher serum drug levels
and an increased risk of toxicity. Similarly, impaired kidney function
slows drug excretion, prolonging drug action and further increasing
toxicity risk. This necessitates careful monitoring and dosage
adjustments to prevent adverse effects.
Plasma Protein Binding
Drugs often bind to plasma proteins in the blood, which affects their
distribution. Only unbound drugs can exert therapeutic effects. If two
drugs compete for the same binding sites, one may displace the other,
increasing the concentration of the free drug and potentially leading
to toxicity. For example, diazepam can displace phenytoin, raising
phenytoin's free concentration and risk of adverse effects.
First Pass Effect
The first-pass effect refers to the initial metabolism of a drug in the
liver after oral administration, reducing its concentration before it
reaches systemic circulation. This can decrease the drug's efficacy,
requiring higher doses or alternative administration routes to achieve
the desired therapeutic effect.
