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Examples of salts that improve drug solubility
- Phytoin sodium for injection
- Ampicillin sodium in oral suspension/injection
Solubility of unionized drug
Intrinsic solubilty must be below ___ for a need to be salt form
Less than 1 mg/ml
Salts from weak bases yield more ____ solutions.
Salts from Weak acids yield more ____ solution.s
Minocylcline HCl IV solution has a pH of
2 to 2.8
Salt form has a ______ percent of active drug compared to non-salt form.
Synthetic derivative of a drug that is transformed in vivo to liberate an active drug molecule.
Purpose of prodrug
- Biostability/prolonged action
Erythromycin ethylsuccinate is less soluble than
Erythromycin for better taste (suspension), Bypass gastric degradation (degrade in stomach), and better absorption (more lipophilic).
Phosphate is added to
Increase water solubility, added to create a phosphate-ester derivative.
T/F phosphate ester is the same as a phosphate salt
FALSE Example is disopyramide phosphate
Rate limiting step for absorption
Drug dissolution rate for oral bioavailability
Dissolution of solid in liquid occurs in 2 phases
Interfacial reaction liberates molecules from solid phase
Diffusion of liberated molecules away from solid into the bulk liquid.
Noyes whitney equation dissolution rate
Terms for dissolution equation
- dm/dt= mass dissolved in time
- A is surface area
- Cs is drug solubility
- C is concentration
- k is dissolution rate constant
- D is diffusion coefficient of solute in medium
- h is thickness of static boundary layer
Dissolution equation affected by
Size, Solubility in water, volume of dissolution medium, and thickness of static boundary.
to move from one phase to another (polar and nonpolar phases)
Partition is important to
Traverse lipid bilayers
Oil over water
- Into fat
- Into microorganisms
- Into plastic
- between oil and water
Most common organic solvent used
Octanol because it mimics membrane
Butanol mimics ______
Chloroform mimics _____
- Buccal membrane
- Blood brain barrier
Unionized drug has higher partition coefficient and is
Drug absorption most likely found in regions with pHs
favoring unionized form