JC Pharmacology Wk 9 Chapter 20

• Tetracyclines and Sulfonamides are older broad-spectrum bacteriostatic medications.
• They are rarely used for systemic infections due to antimicrobial resistance.
• They are not favoured due to development of more effective, less toxic medications.
• Urinary antiseptics are used only in UTIs.

Tetracyclines

• Effective against a wide range of gram(+) and gram(-) microbes.
• They are not usually the drug of choice.
• These drugs distribute widely into most body tissues and fluids.
• Older tetracycline medications are excreted mainly in urine.
• Doxycycline is eliminated in urine and feces.
• Minocycline is eliminated mainly by the liver, but also in urine.
• Tetracycline is the prototype.
• Further examples of drugs include: Doxycycline (Vibramycin), Eravacycline (Xerava), Demeclocycline, Minocycline (Minocin), Omadacycline (Nuzyra), Sarecycline (Seysara), Tigecycline (Tygacil).

Sulfonamides

• These are bacteriostatic against a wide range of gram(+) and gram(-) microbes.
• Increasing resistance contributes to decreasing efficacy.
• Susceptibility should be documented by culture and sensitivity testing.
• Some sulfonamides can treat systemic infections, while others have local effects only.
• Trimethoprim-sulfamethoxazole (Bactrim) is the prototype.
• Other examples of drugs include: Mafenide (Sulfamylon), Sulfadiazine, Sulfasalazine (Azulfidine), Silver sulfadiazine (Silvadene).

Question 1

• True or False: Tetracyclines and sulfonamides are older bacteriostatic medications that are rarely used for systemic infections.
• Answer: True.
• Rationale: Tetracyclines and sulfonamides are older, broad-spectrum bacteriostatic medications that are rarely used for systemic infections because of microbial resistance and the development of more effective or less toxic drugs.

Urinary Antiseptics

• Can become bactericidal due to high concentration levels in renal tubules and urine.
• These medications are not used for systemic infections.
• Do not attain therapeutic plasma levels.

Mechanisms of Action

• Tetracyclines penetrate microbial cells, inhibiting protein synthesis.
• Sulfonamides halt multiplication of new bacteria.
• Sulfonamides do not kill mature, fully formed bacteria.

Question 2

• True or False: Phenazopyridine is an antimicrobial used in the treatment of UTIs.
• Answer: False.
• Rationale: Phenazopyridine provides pain relief linked to UTIs, but it is not an antimicrobial medication.

Tetracycline Indications

• Tetracyclines are a drug of choice in the treatment of specific infections like cholera, Rocky Mountain spotted fever, syphilis, typhus, and H. pylori.
• Useful in animal bites and Lyme disease.
• Can be used for chlamydia infections and as an adjunct in STD treatment.
• Also for prophylaxis/treatment of anthrax and long-term acne treatment.
• Substitute for penicillin in hypersensitivity cases.

Sulfonamide Indications

• Used for severe UTIs caused by organisms like E. coli, Proteus and Klebsiella.
• Can treat P. jirovecii pneumonitis.
• Sometimes used in combination to treat chronic bronchitis.
• Can be used for ulcerative colitis and other uncommon infections.
• Topically used for prevention of burn wound infections, ocular and other soft tissue infections.

Urinary Antiseptic Indications

• Urinary antiseptics are used only for UTIs.
• Example drugs include: Nitrofurantoin (Macrobid), Phenazopyridine (Pyridium), Trimethoprim.

Contraindications

• Tetracyclines should not be given to:
  • Patients with kidney failure
  • Pregnant females
  • Children under 8 years old
  • Can discolor tooth enamel and depress bone growth
• Sulfonamides should not be given to:
  • Infants under 2 months

Principles of Therapy - Tetracyclines

• Culture and susceptibility studies are needed before therapy begins.
• This is due to drug resistance.
• The Oral route is effective and preferred.
• Tetracyclines decompose with age, light exposure, extreme heat, and humidity.
• Medications must be stored correctly.

Principles of Therapy - Sulfonamides and Urinary Antiseptics

• Culture and susceptibility studies are needed before therapy begins.
• A loading dose produces therapeutic blood levels more quickly.
• Loading dose = twice maintenance dose.
• Urine pH is important in pharmacotherapy.

Question 3

• True or False: Tetracyclines can be prescribed for the treatment of specific STDs.
• Answer: True.
• Rationale: Tetracyclines can be prescribed for the treatment of certain chlamydial infections, pelvic inflammatory disease, and sexually transmitted diseases.

Special Population Use

• Children
• Older adults
• Abnormal kidney function
• Hepatic impairment
• Critical illness

Tetracyclines and Sulfonamides are broad-spectrum bacteriostatic medications, not often used for systemic infections due to resistance and the availability of more effective, less toxic options. Tetracyclines are effective against many microbes and distribute widely in the body. Sulfonamides are also bacteriostatic against a range of microbes.