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Questions and Answers
Which of the following tetracyclines is specifically used in the treatment of Lyme disease?
Which of the following tetracyclines is specifically used in the treatment of Lyme disease?
What is a notable effect of fetal exposure to tetracyclines?
What is a notable effect of fetal exposure to tetracyclines?
What kind of infections can tigecycline effectively treat?
What kind of infections can tigecycline effectively treat?
What is the primary mechanism of action of antibiotics that inhibit microbial protein synthesis?
What is the primary mechanism of action of antibiotics that inhibit microbial protein synthesis?
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Which tetracycline is used to manage patients with ADH-secreting tumors?
Which tetracycline is used to manage patients with ADH-secreting tumors?
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Which of the following antibiotics is typically considered bactericidal against certain strains of Haemophilus influenzae?
Which of the following antibiotics is typically considered bactericidal against certain strains of Haemophilus influenzae?
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What potential toxicity is associated with the use of outdated tetracyclines?
What potential toxicity is associated with the use of outdated tetracyclines?
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Which macrolide has its absorption impaired by food?
Which macrolide has its absorption impaired by food?
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Which antibiotics are primarily classified as bacteriostatic inhibitors of protein synthesis?
Which antibiotics are primarily classified as bacteriostatic inhibitors of protein synthesis?
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What is a common side effect associated with the use of chloramphenicol?
What is a common side effect associated with the use of chloramphenicol?
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Which of the following is a common adverse effect of doxycycline?
Which of the following is a common adverse effect of doxycycline?
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Which of the following infections is treated with tetracycline specifically?
Which of the following infections is treated with tetracycline specifically?
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What type of resistance mechanism is commonly associated with chloramphenicol?
What type of resistance mechanism is commonly associated with chloramphenicol?
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Which bacterial species is NOT susceptible to chloramphenicol?
Which bacterial species is NOT susceptible to chloramphenicol?
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For which condition is chloramphenicol primarily used as a backup treatment?
For which condition is chloramphenicol primarily used as a backup treatment?
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What property of chloramphenicol allows it to cross the blood-brain barrier?
What property of chloramphenicol allows it to cross the blood-brain barrier?
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What type of bacteria is linezolid primarily effective against?
What type of bacteria is linezolid primarily effective against?
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What is a known side effect of linezolid that may occur in immunosuppressed patients?
What is a known side effect of linezolid that may occur in immunosuppressed patients?
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How does linezolid differ from other protein synthesis inhibitors?
How does linezolid differ from other protein synthesis inhibitors?
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What is the mechanism of resistance seen in very rare cases with linezolid?
What is the mechanism of resistance seen in very rare cases with linezolid?
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What effect does linezolid have on CYP3A4?
What effect does linezolid have on CYP3A4?
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Which macrolide has the longest half-life, making it unique in its elimination process?
Which macrolide has the longest half-life, making it unique in its elimination process?
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Which of the following organisms is most effectively treated by azithromycin compared to erythromycin?
Which of the following organisms is most effectively treated by azithromycin compared to erythromycin?
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What is a common adverse effect associated with erythromycin?
What is a common adverse effect associated with erythromycin?
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Which macrolide is specifically indicated for the prophylaxis against Mycobacterium avium complex?
Which macrolide is specifically indicated for the prophylaxis against Mycobacterium avium complex?
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Fidaxomicin is particularly effective for treating which condition?
Fidaxomicin is particularly effective for treating which condition?
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What is the mechanism of action of fidaxomicin?
What is the mechanism of action of fidaxomicin?
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What is the primary mode of elimination for erythromycin?
What is the primary mode of elimination for erythromycin?
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Which macrolide has shown efficacy in treating ulcers caused by Helicobacter pylori?
Which macrolide has shown efficacy in treating ulcers caused by Helicobacter pylori?
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What is a primary adverse effect associated with telithromycin?
What is a primary adverse effect associated with telithromycin?
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Which drug is structurally related to macrolides but has different resistance mechanisms?
Which drug is structurally related to macrolides but has different resistance mechanisms?
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Which mechanism of resistance is associated with clindamycin?
Which mechanism of resistance is associated with clindamycin?
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What is a common clinical use of clindamycin?
What is a common clinical use of clindamycin?
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Which of the following drugs is known to increase plasma levels of other medications?
Which of the following drugs is known to increase plasma levels of other medications?
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What distinguishes telithromycin from erythromycin?
What distinguishes telithromycin from erythromycin?
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Which of the following is true regarding streptogramins?
Which of the following is true regarding streptogramins?
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Which toxicity is associated with clindamycin?
Which toxicity is associated with clindamycin?
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What is the primary consequence of inhibiting red cell maturation in bone marrow?
What is the primary consequence of inhibiting red cell maturation in bone marrow?
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Which of the following is considered a characteristic of Gray baby syndrome?
Which of the following is considered a characteristic of Gray baby syndrome?
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What effect do tetracyclines have when chelating divalent metal ions?
What effect do tetracyclines have when chelating divalent metal ions?
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Which tetracycline is primarily eliminated in feces?
Which tetracycline is primarily eliminated in feces?
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What is the main reason for the widespread resistance to tetracyclines?
What is the main reason for the widespread resistance to tetracyclines?
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Which of the following infections are tetracyclines primarily used to treat?
Which of the following infections are tetracyclines primarily used to treat?
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What is a notable pharmacokinetic property of Tigecycline?
What is a notable pharmacokinetic property of Tigecycline?
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Which statement about tetracycline resistance mechanisms is true?
Which statement about tetracycline resistance mechanisms is true?
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Study Notes
Pharmacology 2 Overview
- Topics covered include Chloramphenicol, Tetracyclines, Macrolides, Clindamycin, Streptogramins, and Linezolid.
Introduction to Drug Action
- Drugs inhibit bacterial protein synthesis by binding to and interfering with ribosomes.
- Most drugs are bacteriostatic, but some are bactericidal against specific organisms.
- Tetracycline and macrolide resistance is common.
Inhibitors of Microbial Protein Synthesis
- Drugs that inhibit protein synthesis vary in chemical structures and antimicrobial activity.
- Chloramphenicol (broad spectrum).
- Macrolides (moderate spectrum).
- Ketolide (moderate spectrum).
- Lincosamides (moderate spectrum).
- Tetracyclines (broad spectrum).
- Streptogramins (broad spectrum).
- Linezolid (moderate spectrum).
Mechanisms of Action
- Most antibiotics reviewed inhibit protein synthesis at the ribosomal level.
- Binding sites for these antibiotics are on the 50S ribosomal subunit.
- Chloramphenicol inhibits transpeptidation by blocking the binding of the aminoacyl moiety of the charged tRNA acceptor site on the mRNA complex.
Chloramphenicol
- Simple and distinctive chemical structure.
- Effective orally and parenterally, crossing placental and blood-brain barriers.
- Undergoes enterohepatic cycling.
- Inactivated by hepatic glucuronosyltransferase.
- Primarily bacteriostatic, but can be bactericidal against some organisms.
- Not effective against Chlamydia species.
- Resistance is plasmid-mediated, occurring through acetyltransferases.
- Limited clinical use due to toxicity.
- Backup drug for severe Salmonella, pneumococcal, and meningococcal infections (in beta-lactam-sensitive patients).
- Sometimes used for rickettsial diseases and infections caused by anaerobes (e.g., Bacteroides fragilis).
- Commonly used as a topical antimicrobial agent.
- Toxicity includes gastrointestinal disturbances, bone marrow suppression, and gray baby syndrome.
- Drug interactions increase elimination half-lives of certain drugs (e.g., phenytoin, tolbutamide, warfarin).
Tetracyclines
- Broad-spectrum bacteriostatic antibiotics with minor differences in activity against specific organisms.
- Free tetracyclines are crystalline amphoteric substances of low solubility.
- Available as hydrochlorides, which are more soluble.
- Tetracycline solutions are acidic and fairly stable
- Tetracyclines chelate divalent metal ions – interfering with absorption and activity.
- Tigecycline is a glycylcycline and a semisynthetic derivative of minocycline.
- Oral absorption may be impaired by food and multivalent cations (calcium, iron, aluminum)
- Tetracyclines may cross the placental barrier
- Tetracyclines undergo enterohepatic cycling.
- Doxycycline is excreted primarily in feces, other tetracyclines in urine.
- Doxycycline and minocycline have longer half-lives than other tetracyclines.
- Tigecycline is formulated for IV use and has a half-life of 30-36h.
- Resistance to most tetracyclines is widespread – mechanisms include efflux pumps and ribosomal protection proteins.
- Resistance does not affect Tigecycline in most organisms
- Primary uses: infections caused by Mycoplasma pneumoniae, Chlamydiae, Rickettsiae, Vibrios, and some spirochetes.
- Secondary uses: treatment of syphilis, respiratory infections caused by susceptible organisms treatment of leptospirosis, and treatment of acne.
- selective uses: treatment of gastrointestinal ulcers caused by helicobacter pylori (tetracycline); Lyme disease (doxycycline); meningococcal carrier state (minocycline); prevention of malaria; treatment of amebiasis
- Tigecycline is for intravenous use and has broad spectrum.
- Toxicity includes gastrointestinal disturbances, bony structure and tooth effects, hepatic toxicity.
- Renal toxicity - one form of renal tubular acidosis (fanconi's syndrome) has been attributed to the use of outdated tetracyclines; Photosensitivity (demeclocycline), Vestibular toxicity (reversible dizziness and vertigo reported)
Macrolides
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Large cyclic lactone ring structures with attached sugars.
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Good oral bioavailability.
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Azithromycin absorption is impeded by food.
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Distribute to most body tissues, but azithromycin concentrates in phagocytes.
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Erythromycin (half-life 2 hours).
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Clarithromycin (half-life 6 hours).
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Azithromycin (half-life 2-4 days).
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Antibacterial activity against Campylobacter, Chlamydia, Mycoplasma, Legionella, gram-positive cocci, and some gram-negative organisms.
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Azithromycin and clarithromycin have greater activity against species of Chlamydia, Mycobacterium avium complex, and Toxoplasma.
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Azithromycin has a similar spectrum of activity, but is more active against H. influenzae, Moraxella catarrhalis, and Neisseria.
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Clinical uses: treatment of urogenital infections; community-acquired pneumonia; prophylaxis against and treatment of M avium complex; component of drug regimens for ulcers caused by H. pylori.
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Fidaxomicin (narrow-spectrum macrolide, inhibits protein synthesis). -Active against Gram positive anaerobes
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Systemic absorption is minimal
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Effective in treatment of C. difficile colitis (possibly lower relapse rate)
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Toxicity includes gastrointestinal irritation, skin rashes, eosinophilia (especially with erythromycin).
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Hypersensitivity-based acute cholestatic hepatitis (with erythromycin estolate).
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Erythromycin inhibits hepatic cytochrome P450, potentially increasing levels of other drugs (anticoagulants, carbamazepine, cisapride, digoxin, and theophylline).
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Toxicity includes gastrointestinal disturbances, bony structure effects, and hepatic toxicity.
Telithromycin (Ketolide)
- Structurally related to macrolides, similar spectrum of activity as erythromycin
- Active against some macrolide-resistant strains.
- Used in community-acquired pneumonia, including infections from multidrug resistant organisms.
- Elimination in bile and urine.
- Adverse effects include hepatic dysfunction, QTc prolongation.
Clindamycin
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Inhibits bacterial protein synthesis via a mechanism similar to macrolides, but not chemically related
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Cross-resistance between clindamycin and macrolides is common
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Mechanisms of resistance include methylation of the 50S ribosome subunit binding site; enzymatic inactivation
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Gram-negative aerobes are intrinsically resistant.
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Good tissue penetration after oral absorption
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Metabolites are eliminated via biliary and renal excretion.
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Clinical uses: severe infections caused by anaerobes; gram-positive cocci; prophylaxis of endocarditis.
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Combination with pyrimethamine for AIDS-related toxoplasmosis.
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Toxicity includes gastrointestinal irritation, skin rashes, neutropenia and possible superinfections (e.g., C. difficile colitis).
Streptogramins
- Combination of two streptogramins (quinupristin-dalfopristin)
- Bactericidal activity with longer duration (post-antibiotic effects).
- Active against pneumococci, MRSA, VRSA & E. Faecium.
- Administered intravenously.
- Potential for pain and arthralgia-myalgia syndrome. -Potent inhibitors of CYP3A4 increasing plasma levels of many drugs (e.g., astemizole, cisapride, cyclosporine, diazepam, non nucleoside reverse transcriptase inhibitors (NNRTI), and warfarin)
Linezolid
- Novel class of antibiotics (oxazolidinones)
- Active against drug-resistant gram-positive cocci (MRSA, PRSP, VRE).
- Active against L. monocytogenes and corynebacteria.
- Binds to unique site on 23S ribosomal RNA of 50S subunit.
- No cross-resistance with other protein synthesis inhibitors.
- Available as oral and parenteral forms
- Eliminated by the liver (4-6 hour half life)
- Toxicity includes thrombocytopenia and neutropenia
- Possible serotonin syndrome when given with SSRIs
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Description
This quiz covers key topics in Pharmacology 2, focusing on various classes of antibiotics including Chloramphenicol, Tetracyclines, and Macrolides. It explores their mechanisms of action, properties, and the challenges of resistance in microbial treatment. Test your knowledge on how these drugs inhibit protein synthesis and their spectrum of activity.
