Phthalylsulfathiazole

Phthalylsulfathiazole (also known as sulfathalidine)^[1] is a sulfonamide broad-spectrum antimicrobial used primarily for treating gastrointestinal infections.^[2][3]

Phthalylsulfathiazole

Clinical data
AHFS/Drugs.com	International Drug Names
ATC code	A07AB02 (WHO)
Identifiers
IUPAC name 2-[({4-[(1,3-Thiazol-2-ylamino)sulfonyl]phenyl}amino)carbonyl]benzoic acid
CAS Number	85-73-4 N
PubChem CID	4806
DrugBank	DB13248 Y
ChemSpider	4641 N
UNII	6875L5852V
KEGG	D02440 Y
ChEMBL	ChEMBL1524273 N
CompTox Dashboard (EPA)	DTXSID8023470
ECHA InfoCard	100.001.480
Chemical and physical data
Formula	C17H13N3O5S2
Molar mass	403.43 g·mol−1
3D model (JSmol)	Interactive image
SMILES C1=CC=C(C(=C1)C(=O)NC2=CC=C(C=C2)S(=O)(=O)NC3=NC=CS3)C(=O)O
InChI InChI=1S/C17H13N3O5S2/c21-15(13-3-1-2-4-14(13)16(22)23)19-11-5-7-12(8-6-11)27(24,25)20-17-18-9-10-26-17/h1-10H,(H,18,20)(H,19,21)(H,22,23) N Key:PBMSWVPMRUJMPE-UHFFFAOYSA-N N
NY (what is this?)  (verify)

Medical uses

Phthalylsulfathiazole is indicated for treating various intestinal conditions, including dysentery, colitis, gastroenteritis, and for preoperative preparation in intestinal surgery.^[2][4] It may be administered in combination with other antimicrobials such as metronidazole, furazolidone, or neomycin for enhanced efficacy.^[3]

Like all antibiotics, phthalylsulfathiazole should be carefully monitored to avoid promoting bacterial resistance.^[3]

Available forms

Phthalylsulfathiazole is typically given orally in tablet form to target intestinal infections directly.^[2] Due to the phthalic acid substitution on the aniline nitrogen, it remains unabsorbed in the bloodstream, focusing its action within the gut.^[5]

Adverse Effects

Common side effects include nausea, stomach upset, and skin rash.^[6] Rare but serious adverse effects may involve vitamin B deficiency, agranulocytosis, or aplastic anemia.^[7]

Mechanism of action

Phthalylsulfathiazole acts by competitive antagonism with para-aminobenzoic acid, inhibiting the dihydropteroate synthetase enzyme crucial for dihydrofolic acid synthesis. This inhibition disrupts purine and pyrimidine synthesis, impairing bacterial growth and reproduction.^[8] Once in the large intestine, phthalylsulfathiazole hydrolyzes to release sulfathiazole, the active antimicrobial component.^[9]