PH1.4-5 | PH1.4-5 | Drug Formulations, Delivery Systems and Administration Routes — SDL Guide — Summary & Reflection

KEY TAKEAWAYS

Drug formulation determines the physical form in which an active ingredient is delivered; formulation choice governs dissolution rate, release profile, protection from gastric acid, and patient acceptability. Major forms include plain tablets, enteric-coated tablets (must NOT crush), SR/XR tablets (must NOT crush), capsules, liquids, semi-solids, MDI/DPI inhalers, transdermal patches, and depot injections.

Route of administration determines the pathway to systemic or local action: enteral (oral, sublingual, rectal), parenteral (IV — 100% bioavailability; IM — vaccines/depots; SC — insulin/LMWH; intrathecal — spinal anaesthesia), and topical/inhaled. The sublingual and IV routes bypass hepatic first-pass metabolism entirely.

First-pass metabolism is the key concept linking formulation choice to route selection: drugs with high first-pass extraction require non-oral routes (sublingual, transdermal, parenteral) or dose adjustment.

Technique matters as much as route selection: MDI requires inhalation-actuation coordination (spacer removes this requirement); SC insulin injections require site rotation; IM depot injections must NOT be massaged; sublingual drugs must NOT be swallowed.

REFLECT

Think of a patient (real or from a case study) who was prescribed an inhaler, insulin, or a sublingual drug. Was the route and formulation explained to them? Was the technique demonstrated and checked? If you were the prescribing physician, what additional counselling would you provide? Write two or three sentences reflecting on how formulation knowledge would change your approach to prescribing and patient education.