Methods to Modify Rate of Drug Absorption
Slow Release Dosage Forms
e.g. retard tablets, spansules, depot injections, subcutaneous implants etc.
Release drug slowly → prolonged action.
Enteric Coated Tablets
Coating prevents the degradation of drug by gastric acid → drug is absorbed from intestine.
Acid labile drugs can be given orally in this form.
Changing Physical Characteristics of the Drug
e.g:
Ultralente insulin
↓
Large crystalline particles which are insoluble in water
↓
release insulin slowly
↓
prolonged action
----
Semilente insulin
↓
Smaller amorphous particles
↓
release insulin fast
↓
quick action
Adding Vasoconstrictor or Applying Tourniquet
↓
decrease blood flow
↓
decrease absorption
e.g. combining vasoconstrictor with local anesthetic to prolong local action and decrease systemic toxicity of anesthetic.
Adding hyaluronidase to the injection
Hyaluronidase breaks down the matrix
↓
promotes the spread of drug
↓
increased absorption.
Rubbing & Massage
Increase absorption.