ED50, Therapeutic Index, and Drug Interactions

Vocabulary flashcards covering ED50, Therapeutic Index, drug-drug interaction outcomes, basic interaction mechanisms, CYP enzyme alterations, and combined toxicity based on the lecture material.

ED50

Average effective dose required for $50\%$ of the population (e.g., $170\,mg$ to raise gastric pH to 5 in $50\%$ of 100 subjects).

Therapeutic Index (TI)

Ratio of $LD50$ to $ED50$, represented as $\text{TI} = \frac{LD50}{ED50}$. A higher TI indicates a relatively safe drug (e.g., Drug X with $\text{TI} = 10$), while a lower TI indicates a relatively unsafe drug (e.g., Drug Y with $\text{TI} = 2$).

Drug Interactions

Alteration of drug efficacy, effect, or safety by drugs, food, or supplements.

Intensification

A drug interaction outcome that can be beneficial (e.g., sulbactam + ampicillin) or detrimental (e.g., aspirin + warfarin).

Reduction

A drug interaction outcome that can be beneficial (e.g., naloxone + morphine) or detrimental (e.g., propranolol + albuterol).

Unique Response

A drug interaction outcome producing a unique clinical response, such as disulfiram + alcohol.

Direct Interactions

A basic drug interaction mechanism involving physical or chemical inactivation in IV solutions.

Pharmacokinetic Interactions

A basic drug interaction mechanism featuring altered absorption, distribution, or metabolism via CYP enzymes.

CYP Induction

Accelerates metabolism of co-administered drugs (e.g., phenobarbital decreases oral contraceptive efficacy).

CYP Inhibition

Slows metabolism, increasing drug levels and toxicity risk (e.g., cobicistat increases atazanavir levels).

Combined Toxicity

A condition resulting from overlapping organ toxicities of combined substances (e.g., alcohol + acetaminophen).