Solution Properties and Pharmaceutical Formulations

Vocabulary practice flashcards covering solution properties, colligative properties, buffers, tonicity, drug absorption factors, excipients, solid-state forms, and delivery considerations.

pH = pKa Ionization State

The state in which a drug or substance is 50% ionized and 50% non-ionized.

Optimal Buffer Condition

The condition met when $\text{pH} = \text{pKa}$, allowing a buffer solution to work at its best.

Effective Range of a Buffer

The operational pH range of a buffer, defined as $\text{pKa} \pm 1\,\text{pH unit}$.

Pharmaceutical Buffer

A solution component designed to resist pH changes and maintain stability, solubility, and patient comfort.

Four Colligative Properties

Vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure.

Colligative Properties Basis

Physical properties that depend on the number of dissolved particles, not the identity of the particles.

Effect of Dissolved Particles on Osmotic Pressure

An effect where having more dissolved particles causes osmotic pressure to increase.

Effect of Dissolved Particles on Boiling Point

An effect where having more dissolved particles causes boiling point to increase.

Effect of Dissolved Particles on Freezing Point

An effect where having more dissolved particles causes freezing point to decrease.

Effect of Dissolved Particles on Vapor Pressure

An effect where having more dissolved particles causes vapor pressure to decrease.

Van't Hoff Factor ($i$)

The number of particles produced when a solute dissolves in a solvent.

Van't Hoff Factor for Sugar

A value equal to $1$, indicating that sugar does not dissociate into multiple particles.

Van't Hoff Factor for NaCl

A value equal to $2$, representing the number of particles produced when sodium chloride dissolves.

Van't Hoff Factor for $\text{CaCl}_2$

A value equal to $3$, representing the number of particles produced when calcium chloride dissolves.

Osmotic Pressure Dependence on Van't Hoff Factor

Osmotic pressure increases as the Van't Hoff factor increases because more particles are present.

Isotonic NaCl Concentration

A sodium chloride solution concentration of $0.9\%\text{ NaCl}$.

Hypotonic Solution Effect on Red Blood Cells

Causes water to enter the cells, leading to hemolysis.

Hemolysis

The swelling and bursting of red blood cells.

Hypertonic Solution Effect on Red Blood Cells

Causes water to leave the cells, leading to crenation.

Crenation

The shrinkage and wrinkling of red blood cells.

Isotonicity Freezing-Point Depression

The freezing-point depression value corresponding to isotonicity, defined as $\Delta T_f = 0.52^\circ\text{C}$.

Solubility

The amount of drug that can dissolve in a solvent.

Importance of Solubility

The principle that a drug must dissolve before it can be absorbed.

Dissolution

The rate at which a drug dissolves.

Bioavailability Impact of Dissolution

Faster dissolution generally leads to faster absorption and improved bioavailability.

Diffusion

Movement of molecules or particles from high concentration to low concentration.

Permeability

The ability of a drug to cross biological membranes.

Bioavailability

The fraction of drug that reaches systemic circulation.

Determinants of Bioavailability

Solubility, dissolution, diffusion, permeability, and ionization.

Viscosity

The resistance of a liquid to flow.

Viscosity Comparison: Water vs. Syrup

Syrup has a higher viscosity than water.

Viscosity Effect on Suspension Stability

Higher viscosity improves stability and decreases sedimentation.

Disadvantages of High Viscosity

Makes formulations harder for pouring, dosing, and injection.

Purpose of Polymers in Formulations

Controlling drug release and improving formulation stability.

Dosage Forms Commonly Using Polymers

Extended-release and controlled-release dosage forms.

Excipient

An inactive ingredient in a formulation.

Benzalkonium Chloride

An excipient that functions as a preservative.

Boric Acid and Sodium Borate

Excipients that function as buffering agents.

Sodium Chloride in Formulations

An excipient used for tonicity adjustment.

Dextrose in Formulations

An excipient used for tonicity adjustment.

Crystalline Drug Form

A drug structure characterized by an ordered structure, greater stability, and lower solubility.

Amorphous Drug Form

A drug structure characterized by a disordered structure, greater solubility, faster dissolution, and lower stability.

Polymorphism

The ability of the same drug to exist in different crystal forms.

Importance of Polymorphism

Different polymorphs can have different stability, solubility, and bioavailability.

Precipitation

The process of a drug coming out of solution.

Consequences of Precipitation

It can reduce potency, stability, and effectiveness.

Dose Dumping

Sudden release of a large amount of drug from a controlled-release dosage form.

Danger of Dose Dumping

It can cause toxicity.

Incompatibility

An undesirable interaction between formulation components.

Consequences of Improper Storage

Can cause drug degradation, instability, and loss of potency.

Essential Ophthalmic Product Properties

Proper pH, proper tonicity, and sterility.

Spacer with a pMDI Inhaler

A device attachment that improves lung deposition and decreases throat deposition.

Primary Beneficiaries of Spacers

Children, older adults, and patients with poor inhaler coordination.

Weak Acid Form at $\text{pH} < \text{pKa}$

The state in which the non-ionized form ($\text{HA}$) predominates.

Weak Acid Form at $\text{pH} > \text{pKa}$

The state in which the ionized form ($\text{A}^-$) predominates.

Weak Base Form at $\text{pH} < \text{pKa}$

The state in which the ionized form ($\text{BH}^+$) predominates.

Weak Base Form at $\text{pH} > \text{pKa}$

The state in which the non-ionized form ($\text{B}$) predominates.

Colligative Properties Summary Rule

More particles results in $\uparrow$ osmotic pressure, $\uparrow$ boiling point, $\downarrow$ freezing point, and $\downarrow$ vapor pressure.

Systemic Circulation Target

The body's central blood stream reached by the fraction of drug measured as bioavailability.

Sedimentation in Suspensions

The settling of particles in a liquid suspension, which decreases as viscosity increases.