L30 - Physiological factors affecting drug absorption 1 Flashcards
(15 cards)
Why are most drugs taken orally?
Most drugs are taken orally due to convenience and well-accepted by patients.
What is the primary site of drug absorption in the gastrointestinal (GI) tract?
The primary site of drug absorption is the small intestine.
What role does gastric fluid play in drug absorption?
Gastric fluid is acidic and contains pepsin enzymes, which can degrade some drugs.
Why are gastro-resistant dosage forms used for certain drugs?
Gastro-resistant dosage forms do not release the drug in acidic conditions.
Why can’t insulin be administered orally?
Insulin is completely degraded by pepsin, making oral administration impossible; it must be administered via subcutaneous injection.
What is the significance of gastric emptying in drug absorption?
The rate of gastric emptying is important for the rate of gastrointestinal absorption.
What is the Biopharmaceutical Classification Scheme (BCS) and how are drugs categorized within it?
The BCS classifies drugs into four classes based on permeability and solubility: Class 1 (highly permeable, highly soluble), Class 2 (highly permeable, poorly soluble), Class 3 (poorly permeable, highly soluble), Class 4 (poorly permeable, poorly soluble).
What does a LogP value indicate about a drug?
A LogP value indicates the balance of hydrophilicity and lipophilicity of a drug, with an ideal range of ~1 to 3.
How can prodrugs improve membrane permeability? Provide an example.
Prodrugs can improve membrane permeability by adding functional groups. For example, bacampicillin is an ester of ampicillin.
How does the type of meal consumed affect gastric emptying rate?
The type of meal can reduce gastric emptying rate, with fatty acids and triglycerides having a significant impact.
What impact do fatty acids and triglycerides have on gastric emptying, and how does chain length or saturation play a role?
Fatty acids and triglycerides reduce gastric emptying rate, with the effect being proportional to concentration and chain length; unsaturated triglycerides reduce emptying more than saturated ones.
List three factors that can reduce gastric emptying rate.
Factors that can reduce gastric emptying rate include: meal volume, type of meal, and certain drugs (e.g., anticholinergics, narcotics).
What is the hepatic first-pass effect?
The hepatic first-pass effect is the reduction of bioavailability due to the first passage of a drug through the liver.
How does the first-pass effect influence the bioavailability of drugs with inactive metabolites?
If the metabolite is inactive, the first-pass effect results in a net loss of drug that reaches systemic circulation.
What are possible strategies to overcome the first-pass effect for drugs with high metabolism in the liver?
Strategies may include using non-oral administration routes or increasing the oral dosage.
