Pharmacology of Sulfonamides

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Questions and Answers

Which infections are indicated for SMZ/TMP (Bactrim)?

Cholera and Rickettsial infections

Uncomplicated UTI and Traveler’s Diarrhea (correct)

Hemophilus influenza and Strep pneumonia

Bacterial vaginosis and PCP

What is the effect of Nitrofurantoin on patients with impaired GFR?

No effect on efficacy

Increased efficacy of treatment

Decrease in efficacy and increased systemic toxicity (correct)

Increased urine concentration

What is a possible mechanism of action for Nitrofurantoin?

Inhibition of bacterial cell wall synthesis

Inhibition of acetyl coenzyme A in bacterial metabolism (correct)

Disruption of DNA replication

Interference with protein synthesis

Which drug is likely to have increased anticoagulant effects when co-administered with SMZ/TMP?

Warfarin Signup and view all the answers

Which bacteria are primarily targeted by Bactrim for bacterial meningitis treatment?

Haemophilus influenza, Strep pneumonia, and Neisseria meningitidis Signup and view all the answers

What should be considered when co-administering Rifampin with certain antibiotics?

Increased risk of birth control failure Signup and view all the answers

Which of the following conditions is associated with the use of Tetracyclines?

Rickettsial infections Signup and view all the answers

Which of the following is NOT a mechanism of bacterial resistance?

Increased drug uptake Signup and view all the answers

Which of the following conditions is not effectively treated with tetracyclines?

Tuberculosis Signup and view all the answers

What is a significant risk associated with the use of tetracyclines in certain populations?

Use in pregnancy or in children Signup and view all the answers

Which bacterial infection is most likely associated with severe dehydration if not treated promptly?

Cholera Signup and view all the answers

What is an atypical use of tetracyclines?

Management of SIADH Signup and view all the answers

Which of the following statements concerning the spectrum of activity of tetracyclines is true?

They have activity against both gram-negative and gram-positive organisms. Signup and view all the answers

What is the primary mechanism of action for sulfonamides in bacterial cells?

Inhibition of dihydropteroate synthetase Signup and view all the answers

Which of the following is NOT a characteristic feature of nitrofurantoin pharmacokinetics?

Biliary excretion predominating its clearance Signup and view all the answers

Which mechanism contributes to bacterial resistance against beta-lactam antibiotics?

Alteration of target sites Signup and view all the answers

Which classes of antibiotics are effective against SPACE organisms?

Carbapenems and Fluoroquinolones Signup and view all the answers

What is a significant drug interaction to consider when prescribing trimethoprim/sulfamethoxazole?

Increased effect of oral anticoagulants Signup and view all the answers

What class of antibiotics primarily exhibits a bactericidal effect?

Beta-lactams Signup and view all the answers

Which statement about the spectrum of activity of trimethoprim/sulfamethoxazole is accurate?

It is effective against both gram-positive and gram-negative bacteria Signup and view all the answers

Which of the following is a common reason bacteria develop resistance to antibiotics?

Active efflux mechanisms Signup and view all the answers

What is the primary factor influencing the utilization of aminoglycosides in treating infections?

Concentration-dependent killing Signup and view all the answers

What is a potential adverse effect associated with the use of sulfonamides?

Hematologic abnormalities Signup and view all the answers

Which of the following best describes the primary reason host cells are not affected by sulfonamides?

Host cells require preformed folic acid and cannot synthesize it. Signup and view all the answers

What pharmacokinetic characteristic is common to sulfonamides?

Excretion via glomerular filtration. Signup and view all the answers

Which mechanism of bacterial resistance involves changes in the structure of dihydropteroate synthetase?

Decreased affinity for sulfonamides due to structural modification. Signup and view all the answers

Which of the following organisms is known to be susceptible to sulfonamides?

Staphylococcus (MRSA) Signup and view all the answers

What adverse effect is associated with the use of sulfonamides during pregnancy?

Kernicterus in neonates due to bilirubin displacement. Signup and view all the answers

What type of drug interaction is most likely to occur with sulfonamides?

Inhibition of anticoagulant metabolism. Signup and view all the answers

Which of the following is a common hypersensitivity reaction associated with sulfonamides?

Steven Johnson Syndrome. Signup and view all the answers

Why is trimethoprim often combined with sulfonamides in treatment?

To provide a synergistic effect against bacteria. Signup and view all the answers

Which of the following antibiotics has a primary spectrum of activity against isolated gram-negative organisms?

Nitrofurantoin Signup and view all the answers

What is a significant adverse reaction associated with the use of expired sulfonamides?

Urticaria and skin rashes. Signup and view all the answers

What is the primary mechanism by which Trimethoprim exerts its antibacterial effect?

Inhibition of dihydrofolate reductase Signup and view all the answers

Which condition is NOT indicated for the use of sulfonamides?

Osteomyelitis Signup and view all the answers

Which of the following adverse effects is particularly concerning for patients with folate deficiency when using Trimethoprim?

Hematologic reactions Signup and view all the answers

What is the anticipated effect of combining Trimethoprim and Sulfamethoxazole?

Synergistic bactericidal activity Signup and view all the answers

Which bacteria is specifically noted for its susceptibility to Trimethoprim?

Escherichia coli Signup and view all the answers

Trimethoprim is primarily excreted by which mechanism?

Active renal secretion and glomerular filtration Signup and view all the answers

Which statement is true regarding the spectrum of activity of Bactrim (Trimethoprim/Sulfamethoxazole)?

It has a broad activity against both Gram-positive and Gram-negative organisms. Signup and view all the answers

What is a common mechanism of bacterial resistance to Trimethoprim?

Production of an alternative dihydrofolate reductase Signup and view all the answers

In which patient population is caution advised when prescribing Trimethoprim due to possible folate deficiency?

Pregnant women and alcoholics Signup and view all the answers

Which Gram-negative organism is specifically noted to have resistance against Trimethoprim?

Pseudomonas aeruginosa Signup and view all the answers

Study Notes

Indications for SMZ/TMP (Bactrim)

Effective against urinary tract infections (UTIs), gastrointestinal infections, respiratory tract infections (RTIs), and sexually transmitted diseases (STDs).
Used in prophylaxis for uncomplicated UTIs and acute/chronic prostatitis.
Treats traveler’s diarrhea, cholera, and pneumocystis carinii pneumonia (PCP).

Drug Interactions and Precautions

Warfarin: Increases anticoagulant effects, necessitating monitoring.
Methotrexate: Sulfonamides may displace methotrexate from protein binding, leading to increased free levels.

Nitrofurantoin

Mechanism of action is unclear but may inhibit early bacterial carbohydrate metabolism.
High renal excretion; ineffective if creatinine clearance (CrCl) is less than 50 mcg/ml.
Primarily used for UTIs due to high urine concentration of the drug.

Indications for Trimethoprim

Used for acute uncomplicated UTIs, recurrent UTI prophylaxis, and traveler’s diarrhea treatment and prophylaxis.
Effective against Gram-positive and Gram-negative bacteria, and some protozoa like Pneumocystis carinii.

Mechanism of Action: Trimethoprim

Non-sulfonamide analogue inhibiting dihydrofolate reductase, leading to disruption in folic acid synthesis.
More effective against bacterial dihydrofolate than human counterparts, making it bacteriostatic or bactericidal based on growth conditions.

Spectrum of Activity: Trimethoprim

Covers various strains including Staphylococcus, Streptococcus, E. coli, Klebsiella pneumonia, and others.
Highlights the importance of using in conjunction with dapsone for specific cases.

Sulfonamides Mechanism and Pharmacokinetics

Mimic para-aminobenzoic acid (PABA), inhibiting bacterial folic acid synthesis.
Excreted through glomerular filtration, commonly used for UTIs due to good renal clearance.

Adverse Reactions to Sulfonamides

Include anaphylaxis, skin rashes (Stevens-Johnson syndrome), and nephrotoxicity.
Risks of kernicterus in newborns when exposed during the last months of pregnancy.

Classes of Antibiotics

Include penicillins, cephalosporins, aminoglycosides, and tetracyclines, each with specific mechanisms targeting bacterial cell walls or protein synthesis.
Quinolones and tetracyclines cover atypical infections and demonstrate unique bactericidal properties.

Tetracyclines Clinical Uses

Effective against brucellosis, cholera, and Borrelia burgdorferi (Lyme disease).
Demeclocycline is the only tetracycline used for SIADH.

Key Takeaways

Avoid tetracyclines in pregnant women and young children.
Monitor interactions with drugs like rifampin and warn against use of certain birth control methods concurrently with antibiotics.

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Description

Explore the key concepts of sulfonamides and their pharmacokinetics in this quiz. Learn about the folic acid pathway, how sulfonamides function as bacteriostatic agents, and their common uses in treating UTIs. Test your understanding of adverse reactions and the biochemical processes involved.