Tetracycline Antibiotics Overview

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Questions and Answers

What is the mechanism of action of tetracyclines?

Inhibit DNA replication

Inhibit RNA transcription

Inhibit cell wall synthesis

Inhibit protein synthesis by binding to the 30S ribosomal subunit (correct)

Which of the following is a long-acting tetracycline?

Oxytetracycline

Demeclocycline

Doxycycline (correct)

Chlortetracycline

What is a common adverse effect associated with tetracyclines?

Ototoxicity

Cardiac arrhythmias

Nephrotoxicity (correct)

Pulmonary toxicity

Which of the following contributes to the resistance against tetracyclines?

Efflux pump mechanism Signup and view all the answers

Which patients could benefit from tetracycline administration despite renal insufficiency?

Patients requiring treatment for Rocky Mountain spotted fever Signup and view all the answers

What effect do dairy foods have on tetracycline absorption?

Decrease absorption by forming nonabsorbable chelates Signup and view all the answers

Which class of drugs acts on the 30S ribosomal subunit aside from tetracyclines?

Aminoglycosides Signup and view all the answers

Which of the following therapeutic uses is NOT typically associated with tetracyclines?

Tuberculosis Signup and view all the answers

What is the primary mechanism of action of aminoglycosides?

Interfering with the 30S ribosomal subunit Signup and view all the answers

Which of the following is a contraindication for using tetracycline antibiotics?

Pregnant women Signup and view all the answers

What type of infections are aminoglycosides typically used to treat?

Serious infections with aerobic gram-negative bacilli Signup and view all the answers

What is a common adverse effect associated with aminoglycosides?

Ototoxicity Signup and view all the answers

Which mechanism is NOT involved in resistance to aminoglycosides?

Inhibition of metabolic pathways Signup and view all the answers

Which of the following describes the action of chloramphenicol?

Inhibition of peptidyl transferase on the 50S ribosomal subunit Signup and view all the answers

What is a potential adverse effect of chloramphenicol in newborns?

Gray baby syndrome Signup and view all the answers

Which of the following is a characteristic of tetracycline antibiotics?

Bacteriostatic activity Signup and view all the answers

What is the primary mechanism of action for macrolides?

Bind to 50S ribosomal subunit and inhibit protein synthesis Signup and view all the answers

Which of the following antibiotics is known to have a high capacity for causing ototoxicity at high doses?

Clarithromycin Signup and view all the answers

What is one common resistance mechanism against macrolides?

Active efflux pump mechanisms Signup and view all the answers

In which situation can macrolides serve as an alternative treatment?

Infection in penicillin-allergic patients Signup and view all the answers

What serious gastrointestinal adverse effect is associated with Clindamycin?

Pseudomembranous colitis Signup and view all the answers

Which type of infections are clindamycin particularly effective against?

Anaerobic infections and Gram-positive cocci Signup and view all the answers

What is a key adverse effect of macrolides?

Cholestatic jaundice Signup and view all the answers

What is the mechanism of action for Streptogramins?

Bind to the 50S ribosomal subunit and inhibit protein synthesis Signup and view all the answers

Study Notes

Tetracycline

Short-acting: Chlortetracycline, Oxytetracycline, Tetracycline
Intermediate-acting: Demeclocycline, Methacycline
Long-acting: Doxycycline (Vibramycin), Minocycline (Minocin)

Tetracycline Spectrum & Mechanism of Action

Effective against rickettsiae, gram-positive and gram-negative bacteria, chlamydia
Inhibits protein synthesis by binding to the 30S subunit of the bacterial ribosome, preventing the binding of aminoacyl tRNA to the mRNA ribosomal complex
Bacteriostatic

Tetracycline Absorption

Incomplete GI absorption: tetracycline (60-80%), doxycycline (95%), minocycline (100%)
Dairy foods decrease absorption through chelation with calcium ions; also magnesium, iron, and aluminum (antacids)

Tetracycline Distribution

Widely distributed in the body
Bind in tissues undergoing calcification (teeth, bones) or tumors with high calcium content (gastric carcinoma)
Cross the placenta and concentrate in fetal bones and teeth

Tetracycline Excretion

Doxycycline and minocycline are largely excreted in feces, making them suitable for use in renal insufficiency

Tetracycline Resistance

Efflux pump
Enzymatic inactivation
Prevention of binding to ribosomes

Tetracycline Therapeutic Uses

Lyme disease
Mycoplasma pneumonia
Rocky Mountain spotted fever
Acne
Chlamydia
Cholera

Tetracycline Adverse Effects

GI discomfort: anorexia, epigastric pain, abdominal distention, nausea, vomiting, diarrhea, sore mouth, perianal irritation
Hepatotoxicity
Nephrotoxicity
Teeth damage in neonates if doses are not adjusted
Low capacity to glucuronidate antibiotic and underdeveloped renal function in neonates, leading to decreased excretion ability
Poor feeding, cyanosis, and death in neonates

Aminoglycosides

Streptomycin
Gentamycin (Genticin, Gentamycin)
Tobramycin
Amikacin
Kenamycin
Netilmicin
Neomycin (Cicatrin powder, Polyfax ointment)

Aminoglycosides Mechanism of Action

Binds to the 30S ribosomal subunit, interfering with the assembly of the functional ribosomal apparatus or misreading of the genetic code
Effective against aerobic gram-negative bacteria
Bactericidal or bacteriostatic

Aminoglycosides Kinetics

All are parenteral except neomycin
Neomycin is only used topically to reduce intestinal bacteria

Aminoglycosides Resistance

Decreased uptake
Altered receptor
Enzymatic modification

Aminoglycosides Therapeutic Uses

Bacterial endocarditis (in combination with penicillin)
Tuberculosis (in combination with Streptomycin)
Tularemia (hunters skinning infected animals)
Urinary tract infections (E. coli, Enterobacter)
Pneumonia (Pseudomonas, E. coli, Klebsiella)
Meningitis
Peritonitis
Serious infections with Enterobacteriaceae and other aerobic gram-negative bacilli

Aminoglycosides Adverse Effects

Ototoxicity
Nephrotoxicity
Neuromuscular paralysis
Contact dermatitis (neomycin topical)
Monitor peak and trough plasma levels

Macrolides

Erythromycin
Azithromycin
Clarithromycin
Dirithromycin
Troleandomycin
Telithromycin

Macrolides Mechanism of Action

Bind to the 50S subunit of the bacterial ribosome, inhibiting the translocation step of protein synthesis
Bacteriostatic activity
Achieve better intracellular concentrations with gram-positive bacteria
Clarithromycin and Azithromycin are more effective against anaerobes

Macrolides Metabolism

Inhibits the oxidation of other drugs through interaction with the cytochrome P-450 system.

Macrolides Resistance

Inability of the organism to take up the antibiotic
Decreased affinity of the binding site for the antibiotic
Efflux pump

Macrolides Therapeutic Uses

Mycoplasma pneumonia
Syphilis (in penicillin-allergic patients)
Chlamydia (alternative to tetracycline during pregnancy)
Legionellosis pneumonia
Corynebacterium diptheriae carriers (prevention)
Ureaplasma urethritis
Alternative to penicillin in allergic patients
Clarithromycin (Klaricid) and Azithromycin (Azomax) are used for:
- COPD and pneumonia
- Pharyngitis and tonsillitis
- Acute maxillary sinusitis
- Lower respiratory tract infections

Macrolides Adverse Effects

Epigastric distress: nausea, vomiting, pain, diarrhea
Cholestatic jaundice
Ototoxicity (high doses)

Chloramphenicol

Chloramphenicol Mechanism of Action

Binds to the 50S ribosomal subunit, inhibiting the peptidyl transferase step of protein synthesis
Bacteriostatic
Broad spectrum

Chloramphenicol Kinetics

Excretion depends on conversion in the liver to glucuronide, then excretion in the kidneys

Chloramphenicol Therapeutic Uses

Severe odontogenic infections threatening orbital contents or the brain
Typhoid fever (Salmonella)
Refractory meningitis caused by H. influenzae, S. pneumoniae, N. meningitidis, rickettsia, brucella, and Bacteroides

Chloramphenicol Adverse Effects

Anemias
- Hemolytic (reversible and mild)
- Aplastic
Gray baby syndrome (especially in neonates)

Clindamycin

Clindamycin Mechanism of Action

Binds to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis
Bacteriostatic, but bactericidal against susceptible organisms in vivo

Clindamycin Spectrum

Similar to erythromycin
Increased activity against gram-positive and gram-negative anaerobes, including Staphylococcus aureus

Clindamycin Therapeutic Uses

Infections caused by Streptococcus, Staphylococcus, pneumococcus, and anaerobic organisms
Purulent osteitis or other bone infections caused by anaerobes

Clindamycin Adverse Effects

GI distress: diarrhea
Pseudomembranous colitis caused by Clostridium difficile
Superinfections

Streptogramins

Quinupristin-dalfopristin

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Description

This quiz explores the various types of tetracycline antibiotics, their mechanism of action, absorption, and distribution in the body. It covers short-acting, intermediate-acting, and long-acting tetracyclines, delving into their effectiveness against different bacteria and how certain foods affect their absorption. Test your knowledge of these important antibiotics!