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==Introduction==

|linkpage =WikiDrugs

|linktext =WikiDrugs

|sublink1 = Antibiotics

|subtext1 = Antibiotics

 

 

Sulphonamides are derivatives of sulphanilamide, an active metabolite of the pro-drug and dye prontosil. Commonly used ones are: '''sulphadiazine, sulphaquinoxaline, sulphadimethoxine, sulphadoxine''' and '''sulphanilamide'''.

Sulphonamides are derivatives of sulphanilamide, an active metabolite of the pro-drug and dye prontosil. Commonly used ones are: '''sulphadiazine, sulphaquinoxaline, sulphadimethoxine, sulphadoxine''' and '''sulphanilamide'''.

==Mechanism of Action==

==Mechanism of Action==

Sulphonamides act by competing with an essential precursor in folic acid synthesis in bacteria. Bacteria need to synthesise folic acid in order to grow as they are unable to obtain it from their 'diet' like mammals can. Since the bacterium is unable to synthesize RNA or DNA, due to its lack of folic acid, its growth is inhibited. As such, sulphonamides are '''bacteriostatic'''.

Sulphonamides act by competing with an essential precursor in folic acid synthesis in bacteria. Bacteria need to synthesise folic acid in order to grow as they are unable to obtain it from their 'diet' like mammals can. Since the bacterium is unable to synthesize RNA or DNA, due to its lack of folic acid, its growth is inhibited. As such, sulphonamides are '''bacteriostatic'''.

==Spectrum of Activity==

==Spectrum of Activity==

These are generally broad spectrum antibiotics.

These are generally broad spectrum antibiotics.

* They are active against aerobic gram-positive cocci and some rods.

* They are active against aerobic gram-positive cocci and some rods.

* They are active against gram-negative rods, including enterobacteriaceae.

* They are active against gram-negative rods, including enterobacteriaceae.

* They are active against the anaerobes, ''Actinomyces'' and ''Fusobacterium'', but inactive against clostridial species and anaerobic cocci.

* They are active against the anaerobes, ''Actinomyces'' and ''Fusobacterium'', but inactive against clostridial species and anaerobic cocci.

* Reistance is now widespread.

* Resistance is now widespread.

* Drugs which contain a PABA nuclear core, such as procaine, antagonise their actions.

* Drugs which contain a PABA nuclear core, such as procaine, antagonise their actions.

==Pharmacokinetic Considerations==

==Pharmacokinetic Considerations==

* Sulphonamides are lipophilic weak acids of varying pKas.  

* Sulphonamides are lipophilic weak acids of varying pKas.  

* Most are absorbed readily from the gut, except Succinylsulphathiazole and Phthalylsuphathiazole.

* Most are absorbed readily from the gut, except Succinylsulphathiazole and Phthalylsuphathiazole.

* Sulphonamides inhibit thyroid gland function and so mild signs of hypothyroidism have been seen in dogs that have had intesive dosage regimens.

* Sulphonamides inhibit thyroid gland function and so mild signs of hypothyroidism have been seen in dogs that have had intesive dosage regimens.

===Hepatotoxixity===

===Hepatotoxicity===

 

*some of these casue hepatic necrosis in susceptible animals

*some of these casue hepatic necrosis in susceptible animals

*has been associated with a reduced capability of detoxifying the metabolites

*has been associated with a reduced capability of detoxifying the metabolites

*Doberman Pincher breed appear to be susceptible

*Doberman Pinscher breed appears to be susceptible

[[Category:Hepatotoxicity,_Drug_induced]]

[[Category:Hepatotoxicity,_Drug_induced]]