Science of Medicines: Routes of Drug Administration I

This set of vocabulary flashcards covers various routes of drug administration (enteral, parenteral, topical, transdermal, pulmonary), dosage forms, first-pass metabolism, and pharmacokinetic parameters based on the MSOP1014 lecture notes.

Enteral

oral, sublingual, and rectal delivery

Parenteral

sterile preparations administered by injection, such as IV, IM, or SC

Topical

local treatment or application of medications

Transdermal Drug Delivery Systems (TDDSs)

Formulations that facilitate the passage of therapeutic quantities of drug substances through the skin and into the general circulation for a systemic effect.

First pass metabolism

A physiological process where drugs absorbed from the GI tract enter the hepatic portal circulation and are metabolized by liver microsomal enzymes before reaching general circulation.

Bioavailability

The fraction or amount of an administered dose of a drug that reaches the systemic circulation in an unchanged form.

Sublingual delivery

Administration via the mucosa of the ventral surface of the tongue and the floor of the mouth under the tongue.

Buccal delivery

Administration via the epithelial lining of the cheeks, gums, and upper and lower lips.

Intravenous (IV)

Administration directly into a vein that provides 100% bioavailability and immediate response.

Intramuscular (IM)

Injection directly into striated muscle fibers beneath the subcutaneous layer, such as the Gluteal, Deltoid, or Vastus lateralis.

Subcutaneous (SC)

Administration into the layer of fat below the dermis; the maximum volume injected comfortably is generally $1.3\,ml$.

Intrathecal

Administration of a drug directly into the cerebrospinal fluid.

Intraocular

Administration into the eye, for example, into the vitreous humour.

Log P

The octanol/water partition coefficient; for buccal/sublingual formulations, an ideal property is a value > 2.0.

Small molecular size

A physicochemical property ideal for buccal/sublingual delivery, categorized as being < 800\,Da.

O/W Emulsions

Oil-in-water systems containing approximately $10\%$ oil, commonly used for IV injection and Total Parenteral Nutrition (TPN).

Dry powder for Injection

Dosage forms produced mainly by freeze-drying that must be aseptically reconstituted using a sterile vehicle before administration.

Pulmonary administration

Delivery of respiratory drugs directly through the airways to achieve local effects for diseases like Asthma/COPD or systemic effects.

Inertial impaction

A particle deposition pattern in the respiratory tract occurring in the tracheal region for particles with a size > 6\,\mu m.

Sedimentation

A particle deposition pattern in the bronchiolar region for particles with a size between $2-5\,\mu m$.

Diffusion

A particle deposition pattern in the alveolar region for particles with a size < 2\,\mu m.

MDIs

Metered-Dose Inhalers.

DPIs

Dry-Powder Inhalers.

nebulisers

Devices that convert liquid medication into aerosol for inhalation

Pharmacokinetics

The study of drug Absorption, Distribution, Metabolism, and Elimination (ADME).

Biopharmaceutics

The study of how the physicochemical properties of a drug affect the onset, duration, and intensity of activity.

MEC

Minimum Effective Concentration.

MTC

Maximum Tolerated Concentration.

Cmax

The maximum concentration of a drug achieved in the systemic circulation.

tmax

The time taken to reach the maximum concentration ($C_{max}$).

AUC

Area Under the Curve, representing total drug exposure over time.

Oral (GI tract) physiological environment and relevant characteristics

• stomach (acidic), intestine (neutral-alkaline)

• variable pH, digestive enzymes, long transit time, first-pass through liver

Sublingual/buccal physiological environment and relevant characteristics

• highly vascular mucosa

• thin epithelium, rich blood supply, no first-pass entry

Rectal physiological environment and relevant characteristics

• mucosal lining, mixed drainage

• partial systemic absorption, moderate enzymatic activity

IV physiological environment and relevant characteristics

• direct entry to blood stream

• no absorption required, immediate distribution with blood flow

IM physiological environment and relevant characteristics

• muscle tissue

• moderate vascularity, interstitial fluid distribution

SC physiological environment and relevant characteristics

• subcutaneous fat laer

• lower blood flow, slow, steady uptake

Topical physiological environment and relevant characteristics

• epidermis, especially stratum corneum

• strong barrier function, regional thickness differences

Transdermal physiological environment and relevant characteristics

• dermal capillary network

• requires permeation through skin layers, controlled uptake

Inhalation (pulmonary) physiological environment and relevant characteristics

• alveoli and bronchial mucosa

• high surface area, thin diffusion membrane, mucociliary clearance