Prodrug/Sulphanomides

Beschreibung

Karteikarten am Prodrug/Sulphanomides, erstellt von Valentina Valenz am 17/05/2016.
Valentina Valenz
Karteikarten von Valentina Valenz, aktualisiert more than 1 year ago
Valentina Valenz
Erstellt von Valentina Valenz vor mehr als 8 Jahre
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Zusammenfassung der Ressource

Frage Antworten
EXAMPLES Aspirin (prodrug) --> salicylic acid (active agent) Phenacetin (prodrug) --> paracetamol (active agent)
TRANSPORT CHARACTERISTICS prodrugs can interfere with transport (EXAMPLE: putting hydrophilic group may restrict gut to one specific area)
PHARMACEUTICAL PROBLEMS - poor water solubility - aesthetic properties such as taste or tissue irritation - formulation problems
PHARMOKINETIC PROBLEMS - incomplete absorption of the drug across biological barriers - too rapid absorption or excretion - poor site specificty
PHARMACEUTICAL SOLUTION 1 improve flavour of drug by decreasing water solubility so drug does not dissolve on the tongue (CHLORAMPHENICOL = OH --> alkyl chain)
PHARMACEUTICAL SOLUTION 2 reduce pain by improving water solubility. injections hurt, however when made more soluble they hurt less (CLINDAMYCIN phosphate ester addition)
PHARMACEUTICAL SOLUTION 3 mask drug toxicity side effects (SALICYLIC ACID causes gastric bleeding, ASPRIN doesn't OH --> ester)
SULPHANOMIDE AS A PRODRUG - antibacterial agents, active drug of PRONTOSIL (prodrug) - have a versatile synthesis with many derivates - competes with PABA, PABA is the enzyme active in DHF synthesis
GENERAL SYNTHESIS
SIMILARITIES WITH PABA 1º aryl amine Para substituents Similar charges Polar substituents Van der Waals b/c aromatic H-bonding Ionic factors in substituents Similar lengths (6.9 v. 6.7 Å) Similar widths (2.4 v. 2.3 Å)
ROLE OF DIHYDROFOLATE REDUCTASE DHF --> THF
BIOSYNTHESIS OF FOLATES - DHF plays ket role in synthesis of DNA bases - DHF introduces a methyl group into thymine - synthesis of DHF, THF, 10-fromylTHF -DHF not synthesised in HUMAN bodies -DHF pathway interrupted by Trimethoprim
INHIBITION OF DHF PATHWAY 1 - Trimethoprim and a sulphadrug are combined to hit bacteria - high selectivity to DHF - sulphadrug -> inhibits PABA insertion - Trimethoprim inhibits (DHFR) - effective for bronchial adn urinary tract infections
INHIBITION OF DHF PATHWAY 2 - methotrexate is another inhibitor of DHF - low selectivity for bacteria but block DHFR - used in acute childhood leukemia, does not differentiate between normal and malignant cells - v. toxic with serious side effects
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