Influence of biopharmaceutical factors on dosage form design (07/02/19) Flashcards
What are the key steps in absorption?
- Dissolution
2. Permeation =cross epithelial wall into blood or lymphocytes
What are the key competing processes?
- Transit = removal of dosage form before absorption
2. Stability = break down of drug in gut lumen, gut wall or by liver before reaching blood
What is the Biopharmaceutics Classifiaction System (BCS) criteria and limitations?
- Solubility = max dose strength in 250ml or less over pH1-8
- Permeability = over 90% absorption
Limitations: stability at diff. pH, and binding interaction with gut or contents
What are the different Classes in Biopharmaceutics Classification System?
- Class 1 = high solubility, high permeability
- Class 2 = low solubility, high permeability
- Class 3 = high solubility, low permeability
- Class 4 = low solubility, low permeability
Example of Class 1 drug?
Propanol
Example of Class 2 drug?
Ketoprofen
Example of class 3 drug?
Atenolol, gabapentin
Example of class 4 drug?
furosemide
What is the pH of gastric fluid (both fasted and fed)?
Fasted = 1-3.5
Fed = 3-7 (residence time longer)
When should you take a drug with/after meals?
If the drug is unstable in gastric fluid. (example = penicillin, omeprazole, erythromycin
What is required to measure absolute bioavailability?
Requires measurements of blood plasma drug conc vs time (AUC) after extravascular dosing and after IV administration of drug.
What is required to measure relative bioavailability?
Plasma AUC of a test dosage is compared to a standard dosage form. Both administered by same extravascular route (e.g., oral)
A drug is considered bioequivalant if what factors are met?
‘Bioequivalent’ suggests that the test dosage form will have the same therapeutic effectiveness as the standard form.
Bioequivalent if NO significance difference in: AUC, Tmax, and Cmax
(Tmax and Cmax time at peak and drug concentration at the peak of the [Drug] vs time graph)
