phthalylsulfathiazole

Action and Spectrum

Actions and Spectrum: 

phthalylsulfathiazole’s mechanism of action involves its structural similarity to para-aminobenzoic acid (PABA), a precursor required for folic acid synthesis in bacterial cells. Folic acid is essential for producing DNA, RNA, and proteins. phthalylsulfathiazole competitively inhibits the enzyme dihydropteroate synthase, which is responsible for incorporating PABA into the folic acid synthesis pathway. 

By inhibiting this enzyme, phthalylsulfathiazole disrupts the formation of folic acid, leading to the depletion of essential metabolites required for bacterial growth and reproduction. This ultimately results in the bacteriostatic effect of phthalylsulfathiazole, where bacterial growth is halted. 

phthalylsulfathiazole has a broad spectrum of activity against various Gram-positive and Gram-negative bacteria. Its primary use is in veterinary medicine to treat animals’ gastrointestinal and systemic bacterial infections. It’s worth noting that phthalylsulfathiazole is used less frequently in human medicine due to the availability of other, more effective antibiotics. 

The spectrum of activity of phthalylsulfathiazole includes bacterial species such as: 

• Gram-positive Bacteria: Some Staphylococcus and Streptococcus species. 
• Gram-negative Bacteria: Certain Escherichia coli, Salmonella, and Shigella species. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Nausea 

Acute toxicity 

Agranulocytosis 

Vitamin B insufficiency 

Skin Rash 

Stomach upset 

Hypothyroidism 

Neurological reactions 

Hypoglycaemia 

Pseudomembranous colitis 

Black Box Warning

Black box warning: 

None 

Contraindication / Caution

Contraindications/caution: 

Contraindications: 

• Hypersensitivity: Individuals or animals with known hypersensitivity or allergy to phthalylsulfathiazole or other sulfonamide antibiotics should not use this medication. Hypersensitivity reactions can range from mild skin rashes to severe allergic reactions, including anaphylaxis. 
• Severe Liver or Kidney Dysfunction: phthalylsulfathiazole is metabolized in the liver and excreted through the kidneys. Individuals or animals with severe liver or kidney dysfunction may not be able to properly metabolize and eliminate the drug, leading to potential toxicity.  
• Porphyria: phthalylsulfathiazole and other sulfonamide antibiotics can trigger or exacerbate porphyria, a group of rare disorders that affect heme production, a hemoglobin component. 

Pregnancy / Lactation

Pregnancy consideration: Use only if the potential risks and benefits need to be weighed. 

Lactation: Excretion of the drug in human breast milk is unknown 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

phthalylsulfathiazole interferes with bacterial growth by inhibiting folic acid synthesis, an essential precursor for synthesizing nucleic acids and proteins. It achieves this by competitively inhibiting the enzyme dihydropteroate synthase, which is responsible for incorporating para-aminobenzoic acid (PABA) into the folic acid synthesis pathway. Without sufficient folic acid, bacterial cells cannot replicate or maintain essential cellular functions, leading to the bacteriostatic effect of phthalylsulfathiazole. 

Pharmacokinetics: 

Absorption 

phthalylsulfathiazole is administered orally in tablet or capsule form. It is well-absorbed from the gastrointestinal tract after ingestion. The absorption process allows the drug to enter the bloodstream and distribute to various tissues. 

Distribution 

phthalylsulfathiazole is widely distributed throughout the body, including tissues and body fluids. It can cross the placenta and be detected in breast milk. Its distribution is essential to reach the sites of infection and exert its bacteriostatic effects. 

Metabolism 

phthalylsulfathiazole undergoes metabolism in the liver. One of the primary metabolic pathways involves acetylation, where the drug is acetylated to form acetylated metabolites. These metabolites are less active pharmacologically than the parent compound. 

Elimination and Excretion 

The metabolites of phthalylsulfathiazole, including the acetylated forms, are primarily excreted in the urine. The kidneys play a significant role in eliminating the drug and its metabolites from the body. The elimination half-life of phthalylsulfathiazole varies, but it is relatively short compared to other antibiotics. 

Adminstartion

Administration: 

Oral administration 

phthalylsulfathiazole is typically taken multiple times a day orally. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: phthalylsulfathiazole 

Why do we use phthalylsulfathiazole? 

phthalylsulfathiazole is an antibiotic historically used to treat various bacterial infections in humans and animals. However, its use has become less common over time due to the availability of more effective and less toxic antibiotics.  

• Gastrointestinal Infections: phthalylsulfathiazole was commonly used to treat gastrointestinal tract bacterial infections, including diarrhea caused by susceptible bacteria. It was used to combat infections caused by Escherichia coli, Salmonella, and Shigella. 
• Urinary Tract Infections: In some cases, phthalylsulfathiazole was used to treat urinary tract infections caused by susceptible bacteria. Its mechanism of action involves inhibiting bacterial growth by interfering with the synthesis of folic acid. 
• Respiratory Tract Infections: phthalylsulfathiazole was occasionally used to treat respiratory tract infections caused by certain bacteria.