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Drug Formulation

  • Formulated to allow selective targeting of a tissue site.
  • To avoid pre- or systemic metabolism, 
  • To allow a 24 hour action
  • Different drug formulations allow a treatment regime to be tailored to a patients needs, pharmacological characteristics and disease state.


What determines the drug delivery system we use

  • The dosage
  • The frequency of administration
  • The timing of administration


Oral Medication types

  • Solutions
  • Suspensions
  • Capsules,
  • Tablets
  • Modified release tablets.



Absorption of drugs Via the GI tract:

◦Buccal- above the tongue 

◦Sublingual- underneath the tongue 





  • Young, elderly and patients with swallowing difficulties.
  • May be given via a naso-gastric or PEG tube

  • Drugs given in this way are absorbed extremely rapidly

  • Absorption depends on gastric emptying and is most rapid from the small intestine



  • Young, elderly and patients with swallowing difficulties
  • May be given via a naso-gastric or PEG tube
  •  Absorbed extremely rapidly
  • Dispersions of course drug particles in a liquid phase

  • The dose can be contained in a small volume

  • Good for drugs which are insoluble, unpalatable as they are better tolerated


Tablets and Capsules

Note: Dissolution or tablet break down is the rate limiting step in absorption.

Distinct advantages:

  • Convenience
  • Accuracy of dose
  • Reproducibility
  • Drug stability
  • Ease of mass production


Enteric Coated Tablets

  • Delays disintegration of the tablet until it reaches the small intestine.
  • Tablets are enteric coated to:

◦Protect the drug from stomach acid e.g Omeprazole

◦Protect the stomach from the drug  e.g Aspirin 


Prolonged or Delayed Release Formulations

  • Most disorders required prolonged therapy
  • Maintains drug levels within a therapeutic range
  • Reduces the need for frequent dosing
  • The time course for a drug in the body can be prolonged
  • Ccontains more of the active drug but releases it more slowly over a prolonged period



  •  Synthesised inactive derivatives of an active drug which requires to be metabolically activated after administration
  • Prolongation of duration of action
  • Avoids gut degradation of the drug


Buccal and Sublingual Administration

Ideal method for drugs which have extensive pre-systemic or first pass metabolism.


Forms of rectal Route

  • Suppositoriessolid dosage form that is inserted where it dissolves or melts
  • Creams
  • Liquids




Advantages of rectal route 

  • Useful in the young or old
  • Patients unable to swallow
  • Drugs may be administered rectally:

◦To treat local conditions such as proctitis

◦To achieve systemic absorption (indomethacin)

Bypass pre-systemic metabolism


Vaginal Route

  • Pessaries- a medical device
  • Creams
  • Useful in local disease


Injection based drug delivery system

•Provide fast systemic effects bypassing first-pass metabolism

•Drugs can be administered in unconscious or comatose patients

•Drugs having short half-life can be infused continuously


Intravenous Administration

Useful when:

  • A rapid onset of action is required
  • Careful control of plasma levels is required
  • A drug has a short half-life


Intramuscular Injection

  • The drug is given into the muscle mass
  • May be insoluble or formulated in an oil base
  • Allows a more sustained duration of action up to months
  • Depot Injections contraceptive, neuroleptics
  • May be painful


Subcutaneous Injection

  • A common route of administration
  • Easy to use and bypasses need for venous access
  • Used for insulin, heparin and narcotic analgesics


Types of subcutaneous

  • Dermojet- needleless injection used for mass inoculation (vaccination)
  • Pellet  implantation-drug as a solid pellet is implanted under the skin to provide uniform systemic effect .e.g.testosterone


Transdermal Drug delivery system

  • Adhesive patches containing the drug are applied on the skin
  • The drug crosses the skin surface by diffusion by percutaneous absorption (through skin) and  goes into systemic circulation
  • Bypasses first-pass hepatic inactivation



  • Creams,ointments and skin patches
  • Drugs can be administered to the skin to achieve a local effect i.e steroids or a systemic effect i.e HRT or nitroglycerin.


Skin Patches

  •  Allows the release of a drug from a reservoir into the skin and then into the systemic circulation.
  • Possible to obtain controlled, sustained blood levels of the administered drug such as nicotine, nitroglycerin, opiates, HRT, contraception



  • Used to deliver drugs directly to the lung for local effect or  to achieve a systemic effect I.e anaesthetics
  • Medication administered via a pressurised aerosol, breath actuated aerosol, nebuliser or dry powder device


Advantages and Disadvantages of inhalation?


◦Drug delivered directly to site of action

Little systemic absorption (direct/specific)

Rapid effect

◦Small doses used

◦Reduced adverse effects


◦Patient education is essential


Nanoparticle based drug delivery

  • Precise location
  • More effective & reduce the chances of possible side-effects.
  • Nanocarriers- Nanoparticles,Nanotubule,Nanoshell



  • Cutaneous relates to or affects the skin.
  • Subcutaneous refers to being below the skin (as in a penetrating injury, injection or intravenous line).
  • Percutaneous refers to being passed, done or effected through the skin. For example, some materials pass through exposed skin, causing poisoning.