Pharmacology: Drug Delivery Systems

Conventional Drug Therapy

• Prescribed by healthcare professionals for various medical conditions
• Typically uses FDA-approved medications
• Includes oral tablets, injections, inhalers, or topical treatments
• Focuses on alleviating symptoms and addressing disease causes
• Requires adherence to prescribed dosages and schedules

Delayed-Release Systems

• Formulations designed to release drugs at a specific time or location
• Improves patient compliance by reducing dosing frequency
• Useful for drugs sensitive to stomach acid or needing targeted delivery
• Delivers the drug gradually over an extended period
• Minimizes side effects by delivering the drug where it is needed most

Extended-Release Dosage Forms

• Designed to release medication slowly over an extended period
• Provides a sustained therapeutic effect
• Offers reduced dosing frequency and improved patient compliance
• Maintains a constant drug concentration within the therapeutic range
• Reduces potential side effects from rapid blood level fluctuations
• Examples include extended-release capsules, tablets, patches, and injections

Modified-Release Drug Delivery Systems

• Formulations designed to release medications slowly and consistently over extended time periods
• Includes extended-release, delayed-release, and targeted-release systems
• Reduces dosing frequency and maintains constant drug levels

Principles of Obtaining Prolonged-Action Preparations

• Formulations provide sustained drug release over an extended period, often through slow-release mechanisms
• Factors influencing drug action duration include: formulation design, drug properties, and route of administration
• Toxicity risk may increase with prolonged-action formulations due to extended exposure
• Balancing prolonged action and preventing drug accumulation is crucial in formulation design

Targeted-Release Dosage Forms

• Designed to release medications at a specific site or over a specific time period in the body
• Improves drug effectiveness and reduces side effects
• Examples include enteric-coated tablets, liposomes, and microspheres
• Improves patient compliance by reducing dosing frequency
• Requires careful design and manufacturing for proper targeting and delivery

Key Terms: Bioavailability

• Extent and rate at which a drug is absorbed into the bloodstream and becomes available for use by the body
• Route of administration, first-pass metabolism, and drug interactions affect bioavailability
• Expressed as a percentage, indicating the fraction of the administered dose reaching systemic circulation
• Affected by food, as some drugs are better absorbed on an empty stomach

Biological Half-Life

• Time it takes for a substance to decrease by half through metabolism and elimination in the body
• Crucial factor in determining dosing frequency
• Affected by factors like age, liver function, kidney function, and drug interactions

Controlled Release

• Deliberate, gradual release of a drug over time to maintain a steady concentration in the body
• Enhances patient compliance and drug efficacy
• Achieved through various mechanisms such as matrix systems, reservoir systems, or membrane-controlled systems
• Used in chronic conditions needing consistent drug levels

Delayed-Release

• Designed to release active ingredients at a specific time or location in the body
• Often used to improve drug absorption or reduce side effects
• Has special coatings/formulations to resist stomach acid breakdown
• Especially useful for drugs with a narrow therapeutic window

Dose Dumping

• Rapid, unintended release of a drug from its dosage form, leading to potentially dangerous spikes in blood concentration
• Caused by physical damage to the dosage form, altered drug properties, and drug-drug interactions
• Formulation modifications can prevent dose dumping

Extended-Release

• Formulated to slowly release active ingredients into the bloodstream over an extended period, maintaining a steady drug concentration
• Designed to be taken less frequently than immediate-release formulations
• Helps reduce side effects by steadying drug levels

Modified-Release

• Drug formulations designed to release medication in a controlled manner over an extended period
• Includes various types like extended-release, delayed-release, and sustained-release
• Helps maintain constant drug levels in the bloodstream, improving efficacy and reducing side effects
• Optimizes drug absorption, distribution, metabolism, and excretion (ADME) profiles

Narrow Therapeutic Index

• Medications with a small difference between the therapeutic dose and the toxic dose
• Requires careful dosing to avoid harmful side effects
• Close monitoring of blood levels is crucial
• Individual variation in metabolism affects therapeutic index

Osmotic Pressure

• Pressure exerted by the movement of solvent molecules across a semipermeable membrane to equalize solute concentration on both sides

Peak and Trough Plasma Drug Level

• Highest (peak) and lowest (trough) drug concentrations in the bloodstream after administration
• Peak indicates absorption/distribution; trough measures metabolism/elimination
• Monitoring helps maintain therapeutic drug levels and minimize toxicity

Prodrugs

• Inactive compounds that undergo metabolic conversion to become active drugs in the body
• Improve drug delivery, efficacy, or reduce side effects
• Enhance bioavailability by improving solubility or membrane permeability

Prolonged Release

• Formulations designed to slowly release drugs over an extended period, maintaining therapeutic levels
• Improves patient compliance by reducing dosing frequency
• Results in more stable blood levels and potentially fewer side effects

Steady-State Plasma Concentration

• Point at which the rate of drug input equals the rate of drug elimination, resulting in consistent drug levels over time
• Typically achieved after 4-5 half-lives
• Important for drugs with a narrow therapeutic index to maintain consistent therapeutic effects

Sustained Release

• Drug delivery system designed to release medication gradually over an extended period to maintain consistent blood levels
• Reduces dosing frequency and improves patient adherence
• Useful for chronic conditions
• Enhanced by specialized coatings or matrices

Targeted-Release

• Drug delivery systems designed to release medication at specific locations in the body or over specific timeframes
• Directly targets the desired site, minimizing side effects on other areas

Therapeutic Concentration

• Medication levels in the body producing desired effects without causing significant toxicity
• Maintaining therapeutic concentration is crucial for optimal treatment outcomes

Therapeutic Index

• Compares the therapeutic dose (efficacy) with the toxic dose (harm)
• Higher index indicates safer drug profiles
• Helps determine appropriate dosage ranges for appropriate treatment
• Low index requires careful monitoring

Zero-Order Kinetics

• Constant rate of drug metabolism regardless of drug concentration
• Linear decrease in drug levels over time
• Commonly seen in high-dose scenarios where enzyme systems reach maximum capacity
• Not influenced by changes in drug concentration; excretion mechanisms may exhibit zero-order kinetics