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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


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.


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