Sulfonamides Overview

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Questions and Answers

What is the typical ratio of Sulfamethoxazole to Trimethoprim in the combination therapy?

5 parts Sulfamethoxazole to 1 part Trimethoprim (correct)

4 parts Sulfamethoxazole to 1 part Trimethoprim

6 parts Sulfamethoxazole to 2 parts Trimethoprim

3 parts Sulfamethoxazole to 1 part Trimethoprim

Which of the following infections is NOT typically treated with Trimethoprim and Sulfamethoxazole?

Bacterial respiratory tract infections

Uncomplicated urinary tract infections (correct)

Acute otitis media

Gastrointestinal infections such as Shigellosis

What is one of the highlighted adverse effects associated with Trimethoprim and Sulfamethoxazole therapy?

Hepatic failure

Skin rash (correct)

Kidney dysfunction

Bronchospasm

What is the mode of action of Trimethoprim in the combination therapy?

Blocks bacterial DHFR to inhibit folate production Signup and view all the answers

What type of effect might the combination of Trimethoprim and Sulfamethoxazole exhibit?

Bactericidal effect under certain conditions Signup and view all the answers

What is a significant reason for the reduced use of sulfonamides as a single therapy?

High resistance rates Signup and view all the answers

Sulfamethoxazole is commonly administered with which of the following?

Trimethoprim Signup and view all the answers

Which sulfonamide is classified as an non-absorbed oral agent?

Sulfasalazine Signup and view all the answers

In what condition is sulfasalazine primarily used?

Rheumatoid arthritis Signup and view all the answers

What is the serum half-life of sulfadiazine?

10 hours Signup and view all the answers

Sulfacetamide is primarily used to treat which of the following?

Bacterial conjunctivitis Signup and view all the answers

Which of the following statements best describes the mechanism of action of Sulfonamides?

They act as competitive inhibitors for the enzyme converting PABA. Signup and view all the answers

What is a significant limitation of Sulfonamides regarding bacterial susceptibility?

Some bacteria can utilize pre-formed folate from the environment. Signup and view all the answers

What type of sulfonamide is silver sulfadiazine classified as?

Topical agent Signup and view all the answers

What is the primary cause of resistance to Sulfonamides observed in bacteria?

Mutation in dihydropteroate synthase. Signup and view all the answers

What is the overall incidence rate of adverse effects associated with sulfonamides?

5% Signup and view all the answers

Why is the combination of Sulfonamides and Trimethoprim often beneficial in treatment?

Together, they provide a broader antibacterial spectrum. Signup and view all the answers

Among the following, which bacteria are typically susceptible to Sulfonamides?

Haemophilus influenzae. Signup and view all the answers

What is a noted adverse consequence of Sulfonamide therapy?

Reversible bacterial growth upon discontinuation. Signup and view all the answers

Which of the following statements accurately reflects the antibacterial spectrum of Sulfonamides?

They exhibit poor activity against atypical bacteria. Signup and view all the answers

What type of resistance mechanism is observed through the decreased entry or increased efflux of Sulfonamides in bacteria?

Physical barrier resistance. Signup and view all the answers

Which of the following is a common skin reaction associated with sulfa allergies?

Urticaria Signup and view all the answers

What serious blood-related condition is associated with sulfonamides, particularly at higher doses?

Aplastic Anemia Signup and view all the answers

For which group of patients are sulfonamides contraindicated due to the risk of kernicterus?

Pregnant women near term Signup and view all the answers

What effect do sulfonamides have on warfarin therapy?

Inhibit the metabolism of warfarin Signup and view all the answers

Which adverse effect is most commonly associated with sulfonamides in dehydrated patients?

Acute kidney failure Signup and view all the answers

What is the mechanism of action for Trimethoprim when used with sulfonamides?

It acts as a folate antagonist Signup and view all the answers

Which of the following is NOT a typical adverse effect of sulfonamides?

Severe headache Signup and view all the answers

In patients with glucose-6-phosphate dehydrogenase deficiency, which condition is particularly of concern when taking sulfonamides?

Hemolytic anemia Signup and view all the answers

Study Notes

Sulfonamides

Structural analogs of PABA (Para-AminoBenzoic Acid)
Competitive inhibitors that compete with PABA for binding to the active site of dihydropteroate synthase
Considered folate antagonists
Inhibit the synthesis of dihydrofolic acid, a precursor to tetrahydrofolic acid (THF)
THF is a coenzyme required for the synthesis of purines, pyrimidines, and amino acids
Host cell immune defenses are critical to completely eradicate the pathogen
Reversible effect
If the drug is removed and bacteria have not been destroyed, then bacterial growth may resume
Bacteria that cannot import folate from the environment are susceptible
Humans and some bacteria utilize pre-formed folate from the environment (e.g., diet) and thus are not affected
Broad antibacterial spectrum
Includes Gram-positive, Gram-negative, and some atypical bacteria
Examples of susceptible bacteria include Staphylococcus aureus, Streptococcus pneumoniae, Gram-negative enteric bacteria (e.g., E.coli), Haemophilus influenzae, Listeria monocytogenes
Poor activity against anaerobic bacteria, Pseudomonas aeruginosa, and atypical bacteria
Increasing resistance is a major problem
Resistance is due to mutations in dihydropteroate synthase, decreased entry of Sulfonamides, increased efflux, acquisition of an alternative metabolic pathway to produce dihydrofolic acid, and increased production of dihydropteroate synthase
Use of Sulfonamides as a single therapy has become less common due to increasing resistance
Classified into three groups based on their pharmacological properties: Oral, Absorbed, and Excreted Rapidly; Oral, Non-absorbed; Topical
Commonly used Sulfonamides in each group include Sulfisoxazole, Sulfadiazine, Sulfamethoxazole, Sulfasalazine, Sulfacetamide, and Silver sulfadiazine
Most common adverse effect is hypersensitivity (Sulfa allergy)
Other common adverse effects include skin rash, fever, malaise, Stevens-Johnson Syndrome, exfoliative dermatitis, photosensitivity, anaphylaxis, anorexia, nausea, vomiting, crystalluria, hemolytic anemia, aplastic anemia, hepatomegaly, liver necrosis, and kernicterus
Sulfonamides are excreted by the kidneys
Adjust dose for individuals with significant renal insufficiency
Sulfonamides inhibit CYP2C8 and CYP2C9, potentiating the effects of warfarin and increasing the INR
Avoid administering Sulfonamides with Warfarin if possible

Trimethoprim

Inhibits dihydrofolate reductase (DHFR)
Highly selective for prokaryotic DHFR over mammalian DHFR
Considered a folate antagonist
Available as a single agent or in combination
Typically combined with Sulfamethoxazole (a Sulfonamide) for synergistic effects
Ratio of Sulfamethoxazole to Trimethoprim is usually 5:1
Numerous Gram positive and Gram negative bacteria are sensitive to this combination
Trimethoprim alone is bacteriostatic
When combined with Sulfamethoxazole, the effect may be bactericidal
Resistance is rapidly increasing
Used to treat urinary tract infections, bacterial respiratory tract infections, acute otitis media, acute maxillary sinusitis, gastrointestinal infections (e.g., Shigellosis, Typhoid fever, Acute diarrhea due to E.coli), Pneumocystis jiroveci pneumonia, and other infections
Most common adverse effects are skin conditions (e.g., rash)
Other adverse effects include glossitis, stomatitis, and other effects from the sulfanomide.

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Description

Explore the mechanisms and characteristics of sulfonamides in this quiz. Learn about their role as competitive inhibitors and their impact on bacterial growth by inhibiting the synthesis of folate. This quiz covers the structural analogs of PABA and the spectrum of bacteria they affect.