Section 1: Chemical Kinetics & Zero-Order Reaction Basics

Chemical Kinetics Definition

The study of the exact rate, speed, and microscopic mechanisms of chemical reactions.

Kinetics Practical Significance

Enables pharmacists to predict drug stability, expiration dating, total product shelf-life, and mandatory storage conditions.

Reaction Rate Definition

The absolute physical speed at which a specific chemical reaction progresses over time.

Order of Reaction

Describes the exact mathematical relationship detailing how changing drug concentration physically impacts the rate of degradation.

Zero-Order Reaction Metric

Characterized by a reaction type where the drug is lost at a completely constant amount per unit time.

Zero-Order Concentration Rule

The absolute rate of degradation remains entirely independent of the baseline or remaining drug concentration.

Zero-Order Drug Examples

Clinically exemplified by Warfarin, Heparin, Alcohol, Aspirin, Theophylline, Tolbutamide, Salicylates, and Phenytoin.

Zero-Order Master Equation

Expressed mathematically using the linear formula: Ct = Co - kt.

Zero-Order Formula Variables

Co represents initial concentration, Ct represents concentration remaining at time t, and k represents the zero-order rate constant.

Zero-Order Graphic Plot

Plotting direct concentration remaining versus time produces a perfectly straight, linear line on a regular graph.

Zero-Order Plot Metrics

The y-axis charts concentration remaining, the x-axis charts time, the y-intercept matches Co, and the line slope equals negative k (-k).

Zero-Order Half-Life Behavior

It is not constant and decreases continuously over time as the initial drug concentration drops.

Zero-Order Half-Life Equation

Calculated using the explicit mathematical formula: t0.50 = (0.5 * Co) / k.

Shelf-Life General Definition

The exact time period required for 10% of the active drug material to completely disappear or degrade (t0.90).

Zero-Order Shelf-Life Equation

Calculated using the explicit mathematical formula: t0.90 = (0.1 * Co) / k.