4 - Drug Delivery Modalities & The plasma Concentration Curve Flashcards
What is the most common enteral route of drug administration
Oral — easy to take, can be modified (e.g., enteric-coated, extended-release)
What is the benefit of sublingual administration
Rapid absorption and bypasses first-pass metabolism (e.g., glyceryl trinitrate for angina)
When is rectal administration used
When oral intake isn’t possible; partial bypass of first-pass metabolism (e.g., diazepam for seizures)
Which parenteral route provides the fastest systemic effect
Intravenous (IV) — fast and direct
What is a key feature of intramuscular (IM) administration
Moderate absorption; can be sustained with depot formulations
What is the absorption profile of subcutaneous (SC) administratio
Slower absorption with sustained release
What is the benefit of intrathecal administration
Bypasses the blood–brain barrier (e.g., epidural)
Which route provides rapid systemic absorption of anaesthetics?
Inhalation
What is the effect of topical/cutaneous drug administration
Localised effect (e.g., steroid creams), with some systemic absorption possible (e.g., nicotine patches)
What does the plasma concentration curve describe
Drug concentration in plasma over time after administration
What can we learn from the plasma concentration curve
Onset, peak effect, duration, and therapeutic range
What factors affect the plasma concentration curve
- Route of administration
- Drug formulation (e.g., extended-release)
- Elimination rate (slow vs. fast clearance)
What percentage of body volume is blood plasma
55%
What does blood plasma contain
Proteins
Glucose
Clotting factors
Electrolytes
Hormones
CO2
Drugs.
How are drug concentrations in plasma measured
By mass spectrometry or HPLC, using plasma samples at different time points
What is the therapeutic window
The range between the Minimum Effective Concentration (MEC) and the Maximum Tolerated Concentration (MTC)
What is the goal of repeated dosing
To maintain drug levels within the therapeutic window
What is therapeutic drug monitoring used for
Drugs with a narrow therapeutic window (e.g., HIV medications)
What is the pharmacokinetic profile of IV morphine for acute pain
Rapid peak, short duration
How do oral antibiotics behave pharmacokinetically
Slower absorption, lower peak, longer duration
What is the effect of enteric-coated tablets
Delayed release and prolonged peak effect
Why is IV morphine used for acute pain
- Rapid absorption and effect.
- High peak concentration quickly relieves pain.
- Rapid distribution throughout the body. Ideal when the patient is in agony and needs immediate relief
Why use an IV infusion for antibiotics
Provides longer-term effect without a high systemic peak
Reduces side effects due to lower peak concentration
Delivers a sustained therapeutic level
Offers moderate distribution and elimination — ideal for controlled treatment of infection
What are the benefits of long-term oral antibiotics for infections
Convenient — no need for frequent dosing
Slower absorption and lower peak (reduced side effects)
Slower distribution and elimination — provides extended effect over time. Ideal when compliance and convenience are priorities
