The main objectives of produgs are as follow:

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The main objectives of produgs are as follow
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Improvement of lipophilicity
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Enhancement of water solubility
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Increased metabolic stability
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Improvement of taste
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site specific drug delivery prodrugs

• Prepared from a drug a carrier site of
  transporting the drug from the site of
  application selectively to the target cells.
• e.g.
• Brain specific targeting of a hydrophilic drug
• Lipophilic carrier (a dihydropyridine)
• Result in a lipophilic prodrug

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• Inside the brain
• The lipophilic carrier is converted
  enzymatically
• To a highly hydrophilic charged species which is
  
• locked in the brain and then hydrolyzed back to
  
• the drug and N-methyl nicotinic acid is
  eliminated
• from the brain.

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The dihydropyridine/pyridinium redoxchemical
delivery systemCDS
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XH group on the drug is an amine, hydroxyl or
carboxyl.
Lipophilic prodrug
N-methyl nicotinic acid
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Interference with transport characteristics

• The introduction of a hydrophilic disposable
  moiety into the drug prevent its absorption from
  the gastrointestinal tract.
• e.g.

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Decreased toxicity and adverse reaction

• The presence of the thiol group in Captopril
• is considered as one of the responsible
  factors for the adverse reaction of these drugs.
• The masking of the SH group, which in vivo
• regenerates this group, results in less toxic
  and probably longer acting drug
• .

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Increased duration of action

• Bitolterol is a prodrug form of colterol in which
  the catechol hydroxyl groups have been converted
  to 4-methylbenzoic-
• (p-toloyl) acid esters, providing increased
  lipid solubility and prolonged duration of action.

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Bronchodilator Activity
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• Furthermore, the prodrug is preferentially
  distributed in lung tissues rather than the
  plasma or heart so that the bronchodilator
  effect, following subsequent biotransformation of
  the prodrug, is not associated with undesirable
  cardiovascular effect, and is slow and prolonged.