Pharmaceutics - NAPLEX

$\text{pH}=\text{p}K_a+\log\left(\frac{[A^-]}{[HA]}\right)$. Describes the relationship between pH and the ionization state of a weak acid, where the log ratio of conjugate base to acid shifts the equilibrium.

$\text{pH}=\text{p}K_a+\log\left(\frac{[B]}{[BH^+]}\right)$. Describes the relationship between pH and the ionization state of a weak base, where the log ratio of base to conjugate acid shifts the equilibrium.

pH where ionized and unionized forms are equal ($50%$ each). Represents the equilibrium point where half the molecules are protonated and half deprotonated, indicating equal concentrations of ionized and unionized forms.

$\text{pH}<\text{p}K_a$. At lower pH, the environment favors the protonated, unionized form of the weak acid, enhancing lipid solubility and membrane permeation.

$\text{pH}>\text{p}K_a$. At higher pH, the environment favors the deprotonated, unionized form of the weak base, enhancing lipid solubility and membrane permeation.

$%\text{ionized}=\frac{100}{1+10^{(\text{p}K_a-\text{pH})}}$. Derived from the Henderson-Hasselbalch equation, quantifies the proportion of ionized weak acid molecules based on the pH-pKa difference.

$%\text{ionized}=\frac{100}{1+10^{(\text{pH}-\text{p}K_a)}}$. Derived from the Henderson-Hasselbalch equation, quantifies the proportion of ionized weak base molecules based on the pH-pKa difference.

$\frac{dC}{dt}=\frac{DA}{h}(C_s-C)$. Models the rate of drug dissolution as proportional to the diffusion coefficient, surface area, and concentration gradient across the boundary layer.

Decreasing particle size (increases surface area $A$). Smaller particles provide greater surface area for solvent interaction, accelerating the dissolution process per the Noyes-Whitney equation.

Fraction of administered dose reaching systemic circulation unchanged. Quantifies the extent of drug absorption into the bloodstream without alteration, critical for assessing oral versus intravenous efficacy.

$F=\frac{\text{AUC}{po}}{\text{AUC}{iv}}\times\frac{\text{Dose}{iv}}{\text{Dose}{po}}$. Compares the systemic exposure from oral dosing to intravenous, adjusted for dose differences, to determine absorption efficiency.

Inactive/less active form converted in vivo to active drug. Allows for improved pharmacokinetics, such as enhanced solubility or targeted activation, by metabolic conversion to the therapeutic moiety.

Osmolarity: Osm/L; osmolality: Osm/kg (water). Osmolarity measures solute concentration per liter of solution, while osmolality measures per kilogram of solvent, accounting for temperature-independent properties.

Maintain pH to optimize stability, solubility, and patient acceptability. Resists pH changes from external factors, ensuring consistent drug properties and tolerability in the formulation.

Insoluble solid particles dispersed in a liquid vehicle. Provides a heterogeneous system for poorly soluble drugs, allowing uniform dosing upon shaking for even particle distribution.

Flocculated: fast settling, easy resuspension; deflocculated: slow, caking risk. Flocculation forms loose aggregates that settle quickly but redisperse easily, while deflocculation leads to compact sediments prone to hardening.

Two immiscible liquids with one dispersed in the other, stabilized by emulsifier. Enables delivery of immiscible phases by reducing interfacial tension and preventing coalescence through emulsifier stabilization.

Oil-in-water (O/W). Higher HLB surfactants preferentially stabilize oil droplets in aqueous continuous phase due to greater water affinity.

Water-in-oil (W/O). Lower HLB surfactants preferentially stabilize water droplets in oily continuous phase due to greater oil affinity.

$\text{HLB}_{mix}=f_1\text{HLB}_1+f_2\text{HLB}_2$. Provides a weighted average to achieve the optimal HLB for stabilizing a specific emulsion by blending surfactants.

Free of viable microorganisms (bacteria, fungi, and spores). Ensures absence of living microbes to prevent infection, critical for parenteral and ophthalmic preparations.

Same osmotic pressure as blood/tears; no net water movement. Ensures osmotic equilibrium with physiological fluids, preventing cellular dehydration or swelling upon administration.

Agent added to inhibit microbial growth during storage and use. Prevents contamination and spoilage in products susceptible to repeated exposure, extending shelf life and safety.