Podcast
Questions and Answers
Which factor has the greatest impact on the rate of drug absorption when comparing different administration routes?
Which factor has the greatest impact on the rate of drug absorption when comparing different administration routes?
- The solubility of the drug
- The thickness of tissue
- The blood supply at the site of administration (correct)
- The formulation of the drug
How does a drug's solubility affect its absorption?
How does a drug's solubility affect its absorption?
- Higher solubility allows it to cross the plasma membrane easily. (correct)
- Lower solubility results in a faster absorption.
- Solubility has no effect on absorption.
- Drugs must be solid to be absorbed.
What is the primary benefit of intravascular drug administration?
What is the primary benefit of intravascular drug administration?
- It is always less expensive than oral administration.
- It requires less precise dosing.
- It provides a longer duration of action.
- It bypasses absorption barriers. (correct)
Which of the following descriptions best explains why absorption is faster through the small intestine compared to the skin?
Which of the following descriptions best explains why absorption is faster through the small intestine compared to the skin?
Which condition could potentially slow down the absorption rate of a drug in a subcutaneous injection?
Which condition could potentially slow down the absorption rate of a drug in a subcutaneous injection?
Which type of drugs can pass through the plasma membrane via simple diffusion?
Which type of drugs can pass through the plasma membrane via simple diffusion?
What primarily affects the pharmacological action of a drug after entering systemic circulation?
What primarily affects the pharmacological action of a drug after entering systemic circulation?
Which barrier provides protection to the CNS from harmful substances?
Which barrier provides protection to the CNS from harmful substances?
What factor does NOT affect the distribution of a drug within the body?
What factor does NOT affect the distribution of a drug within the body?
Which of the following describes how water-soluble drugs typically cross plasma membranes?
Which of the following describes how water-soluble drugs typically cross plasma membranes?
What type of tissues are drugs likely to distribute to more slowly?
What type of tissues are drugs likely to distribute to more slowly?
What factor can limit drug distribution across the placental barrier?
What factor can limit drug distribution across the placental barrier?
The permeability of which type of tissue barriers can significantly influence drug absorption?
The permeability of which type of tissue barriers can significantly influence drug absorption?
What is primarily responsible for the irreversible loss of a drug from the plasma?
What is primarily responsible for the irreversible loss of a drug from the plasma?
Which of the following factors can influence the process of renal excretion of drugs?
Which of the following factors can influence the process of renal excretion of drugs?
Which route is primarily used by the body for the excretion of volatile substances?
Which route is primarily used by the body for the excretion of volatile substances?
What percentage of the original drug dose ultimately reaches systemic circulation after absorption and metabolism?
What percentage of the original drug dose ultimately reaches systemic circulation after absorption and metabolism?
Which factor does NOT play a role in the reabsorption of lipid-soluble drugs in the kidneys?
Which factor does NOT play a role in the reabsorption of lipid-soluble drugs in the kidneys?
What term describes the range of drug concentration offering therapeutic effects while minimizing toxicity?
What term describes the range of drug concentration offering therapeutic effects while minimizing toxicity?
Which of the following is a primary site for drug excretion from the body?
Which of the following is a primary site for drug excretion from the body?
How does the solubility of a drug primarily affect its absorption?
How does the solubility of a drug primarily affect its absorption?
Flashcards are hidden until you start studying
Study Notes
Drug Absorption
- Drugs are absorbed from the site of administration into the bloodstream.
- The rate of absorption depends on various factors, including:
- Drug solubility (lipid-soluble drugs are absorbed faster)
- Route of administration – oral vs. intravenous
- Tissue surface area and thickness
- Blood supply at the site of administration
- Example:
- A patient takes a 100mg dose of a drug
- 80 mg of the dose is absorbed from the small intestine and reaches the liver via the hepatic portal vein → 20 mg was not absorbed from the small intestine
- The liver then metabolises the remaining 80 mg → 60 mg is irreversibly lost (eliminated)
- Only 20 % of the original dose reaches the systemic circulation
- The amount of drug that reaches systemic circulation is known as the BIOAVAILABILITY of the drug
Drug Distribution
- The drug is distributed to various body compartments after reaching the systemic circulation.
- Distribution depends on:
- Drug solubility
- Cardiovascular functioning
- Perfusion of the area
- Degree of blood flow
- The permeability of the capillaries
- pH of the area
- Binding of drug to plasma proteins
- Barriers to drug distribution:
- Blood-brain barrier
- Placental barrier
- Intravascular administration:
- Intravenous and intra-arterial routes bypass absorption
- Drugs are immediately distributed around the body.
- Medication (tablet) taken orally must disintegrate, dissolve, and be absorbed from the small intestine into the hepatic portal system before entering the systemic circulation.
Drug Elimination
- The pharmacological effects of a drug continue until it is removed from the body.
- Elimination is the irreversible loss of the drug from the plasma, which occurs through metabolism and excretion.
- The liver is the primary site of elimination due to metabolism.
- Excretion is the irreversible loss of the drug from the body:
- Kidneys excrete most drugs and their metabolites
- Drugs can be eliminated in bile and removed from the body in faeces
- Lungs are the primary route for excretion of volatile substances like inhalation anaesthetics
- Other routes include intestine, salivary, sweat and mammary glands
Renal Excretion
- Kidneys are the main site of drug excretion from the body.
- Free unbound drug can be filtered from the blood into the renal filtrate.
- Lipid-soluble drugs may be reabsorbed from the renal filtrate back into systemic circulation.
- Water-soluble drugs can also be secreted from the blood into the filtrate.
- The process of excretion is dependent on:
- Urinary pH
- Renal function
- Cardiovascular function
Pharmacokinetics - How the Body Affects the Drug
- Pharmacokinetics describes how the body absorbs, distributes, metabolizes, and excretes drugs.
- It is essential for understanding how a drug will act within the body and for determining the most appropriate dosage.
Rational Drug Use: Dosage Regime Development
- The therapeutic range is the concentration of a drug that has a high probability of producing the desired therapeutic effect with a low probability of toxic effects.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
