Pharmacology Quiz on Antibiotics and Antiparasitics

Penicillins

• Treatment of Gonorrhea: Previously treated with procaine penicillin G and probenecid, but now primarily uses 3rd-generation cephalosporin ceftriaxone due to resistance.
• Treatment of Syphilis (Treponema pallidum): Benzathine penicillin G (3-week treatment, single injection).
• Treatment of Meningitis: Penicillin G (benzylpenicillin).
• Side Effects:
  • Allergic reactions: Rash, angioedema, anaphylaxis. Severe blistering and peeling skin (Stevens-Johnson syndrome/toxic epidermal necrolysis) is a significant concern.
  • Gastrointestinal: Diarrhea, pseudomembranous colitis (Clostridioides difficile infection) especially with ampicillin use.
  • Renal: Acute interstitial nephritis, particularly with methicillin.
  • Neurological: Seizures (intrathecal injection).
  • Hematologic: Reduced coagulation (high doses of piperacillin, nafcillin, penicillin G); neutropenia (with nafcillin), prolonged use.
• Prophylaxis for Surgery and Dental Procedures:
  • Dental: Amoxicillin for high-risk bacterial endocarditis cases.
  • Surgical: Ampicillin-sulbactam (Unasyn), cefazolin (a 1st-generation cephalosporin) are used.

Cephalosporins

• Mechanism of Action: Binds to penicillin-binding proteins (PBPs), inhibiting bacterial cell wall synthesis. Less susceptible to penicillinases than penicillins.
• Classes and Uses:
  • 1st generation: Cefazolin (parenteral), cephalexin (oral). Active against gram-positive cocci (staphylococci, streptococci). Limited activity against gram-negative organisms, enterococci, MRSA, and most gram-negative rods. Used for cellulitis and surgical prophylaxis.
  • 2nd generation: Cefaclor, cefuroxime, cefprozil. Less gram-positive activity but more gram-negative coverage, varying activity against different organisms. Used for infections involving anaerobic Bacteroides fragilis (cefotaxime, cefoxitin), and sinus, ear, and respiratory infections with H. influenzae or Moraxella catarrhalis (cefuroxime, cefaclor).
  • 3rd generation: Ceftazidime, cefotaxime; increased gram-negative activity, good blood-brain barrier penetration. Active against many gram-negative organisms including penicillin-resistant pneumococci, Pseudomonas, and other beta-lactamase-producing bacteria. Ceficprone is used for oral treatment of Gonorrhea (alternative to ceftriaxone)
  • 4th generation: Cefepime, ceftaroline. Combines gram-positive activity of 1st-generation cephalosporins with gram-negative activity of 3rd-generation ones. Resistant to beta-lactamases produced by many gram-negatives (including Enterobacter, Klebsiella, Pseudomonas, Serratia). Ceftaroline has notable activity against MRSA.
• Side Effects:
  • Allergies (skin rashes to anaphylaxis); less frequent than with penicillin. Partial cross-reactivity exists between penicillins and cephalosporins—avoidance of cross-allergenic reaction should be applied.
  • Injections: pain at injection site, phlebitis (IV).
  • Combinations: Increased nephrotoxicity with aminoglycosides. Methylthiotetrazole-containing drugs (some cephalosporins) may cause hypoprothrombinemia and disulfiram-like reaction to ethanol.

Monobactams and Carbapenems

• Monobactams (Aztreonam):
  • Mechanism: Inhibits bacterial cell wall synthesis.
  • Uses: Gram-negative infections, synergistic with aminoglycosides.
  • Side Effects: Nausea, vomiting, diarrhea, vertigo, and rarely hepatotoxicity. No cross-reaction with penicillin.
• Carbapenems:
  • Mechanism: Inhibits cell wall synthesis.
  • Uses: Broad-spectrum activity against gram-positive and gram-negative bacteria, anaerobes, and Pseudomonas aeruginosa. Ertapenem has limited Pseudomonas coverage.
  • Side Effects: Nausea, vomiting, diarrhea, eosinophilia/neutropenia, seizures with high doses of imipenem, rare cross-reactions with penicillin. Combinations with beta-lactamase inhibitors (e.g., imipenem-cilastatin) provide enhanced coverage, and are used in the treatment of complicated Utis, hospital-acquired pneumonia and ventilator-acquired pneumonia.

Tetracyclines

• Uses: Mycoplasma pneumonia (adults), chlamydia, rickettsial infections, vibrios, some spirochetes. Alternative in treatment of pneumonia.
• Doxycycline: Lyme disease (early and disseminated), malaria, amebiasis.
• Tetracycline: Helicobacter pylori, meningococcal carrier state.
• Tigecycline: Complicated skin and soft tissue infections, intra-abdominal infections, community-acquired pneumonia.
• Side Effects:
  • General: Gastric irritation, esophagitis, tooth discoloration and hypoplasia, growth stunting, hepatotoxicity, photosensitivity, benign intracranial hypertension (pseudotumor cerebri). Contraindicated in pregnancy and children < 8 years.
  • Tigecycline specific: Nausea, vomiting, acute pancreatitis, liver/kidney dysfunction, photosensitivity, pseudotumor cerebri, permanent teeth discoloration. Decreases warfarin clearance.

Fluoroquinolones

• Mechanism of Action: Inhibits bacterial DNA gyrase and topoisomerase IV, interfering with DNA replication and transcription.
• Uses:
  • GI and GU: Gram-negative infections (e.g., gonorrhea, E. coli, Klebsiella, Pseudomonas). Traveler's diarrhea, typhoid fever, anthrax, and pseudomonas.
  • Respiratory: Community-acquired pneumonia (CAP), including atypical pathogens (chlamydiae, mycoplasma, legionella).
  • Skin/skin structure: Infections including MRSA and Enterococcus using Delafloxacin.
  • Other: Meningococcal carrier state, TB treatment and neutropenic patients prophylaxis.
• Side Effects:
  • Common: Nausea, vomiting, diarrhea.
  • Serious: Tendinitis, tendon rupture, cartilage damage and arthropathy in children and young patients. Avoid in pregnancy and those < 18.
  • Other: Skin rashes, headache, dizziness, insomnia, liver problems, photosensitivity, neurotoxicity, opportunistic infections (Candida). QTc prolongation possible.
• Important Considerations: Often combined with other agents for staphylococcal infections. Avoid in enterococcal infections. Gatifloxacin is available as an ophthalmic solution.

Sulfonamides

• Mechanism: Antimetabolites inhibiting folic acid synthesis.
• Uses:
  • Pneumocystis pneumonia: Trimethoprim-sulfamethoxazole (TMP-SMZ) is the drug of choice.
  • Skin infections: TMP-SMZ, skin and skin structure infections - cellulitis and abscesses.
  • Other infections: Sinusitis, ear and respiratory infections (H. influenzae/M. catarrhalis), nocardiosis, toxoplasmosis, backup for cholera, typhoid, shigellosis, MRSA, Listeria. Sulfasalazine is used for inflammatory bowel disease, Sodium sulfacetamide for bacterial conjunctivitis, silver sulfadiazine for burn wound prophylaxis.
• Side Effects:
  • Common: Fever, rashes, photosensitivity, nausea, vomiting, diarrhea.
  • Serious: Stevens-Johnson syndrome, crystalluria, hemolytic/aplastic anemia, granulocytopenia, thrombocytopenia, leukemoid reactions. Hemolytic reactions are possible in G6PD deficiencies.

Antifungals

• Polyenes (Amphotericin B, Nystatin): Binds to ergosterol, creating pores in fungal membranes.
• Antimetabolites (Flucytosine): Converted to 5-fluorouracil to inhibit nucleic acid synthesis.
• Azoles (Fluconazole, Itraconazole, Voriconazole, Posaconazole): Inhibit ergosterol synthesis.
• Echinocandins: Inhibit β-(1,3)-glucan synthase, impeding cell wall production..
• Allylamines (Terbinafine): Inhibit squalene epoxidase, blocking ergosterol synthesis.
• Other: Griseofulvin, Ciclopirox, Tolnaftate – different mechanisms and targets. Specific indications for each.

Anti-TB Drugs

• First-line Drugs: Isoniazid (INH), Rifampin (RIF), Pyrazinamide (PZA), and Ethambutol (EMB).
• Mechanism of action: Varies but generally disrupting TB bacteria growth.
• Uses and Side Effects:
  • INH: active and latent TB; hepatotoxicity, peripheral neuropathy, CNS effects, lupus syndrome.
  • RIF: active TB, latent TB (INH-resistant cases); hepatotoxicity, orange discoloration, GI upset, flu-like symptoms, drug-interactions.
  • PZA: active TB initial therapy; hepatotoxicity, hyperuricemia, arthralgia, GI upset.
  • EMB: active TB combination therapy; optic neuritis, hyperuricemia, peripheral neuropathy.
• Second-line Drugs: Streptomycin, Ethionamide, Capreomycin; used when first-line drugs are ineffective or not tolerated due to drug resistance or intolerance.

Antimalarials

• Treatment: Chloroquine, artemisinin-based combination therapies (ACTs), quinine, mefloquine. Specific agents are indicated for particular cases and areas (Chloroquine, mefloquine, or Doxycycline are more appropriate for prevention)
• Prevention: Chloroquine, mefloquine, atovaquone-proguanil, and doxycycline.

Antivirals

• Hepatitis B: Nucleoside reverse transcriptase inhibitors (NRTIs) (tenofovir, entecavir, lamivudine).
• Influenza: Neuraminidase inhibitors (oseltamivir, zanamivir, baloxavir marboxil); and Amantadine and Rimantadine (less-commonly used).
• HIV: NRTIs, non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), integrase inhibitors, entry inhibitors.

Aminoglycosides

• Side effects: Ototoxicity and nephrotoxicity (kidney damage). Gentamicin, tobramycin, and amikacin are most commonly associated with nephrotoxicity.

Antiprotozoals

• Metronidazole (pharmacokinetics): Well-absorbed, metabolized in the liver, excreted in urine.
• Filariasis: Diethylcarbamazine (DEC), ivermectin, and albendazole.
• Toxoplasmosis: Pyrimethamine (with sulfadiazine), clindamycin, spiramycin, or atovaquone.
• Tapeworm infections: Praziquantel, niclosamide, and albendazole.

Opiates

• Mechanism of Action: Bind opioid receptors in the CNS, mimicking endogenous peptides. Inhibit adenylyl cyclase, increase postsynaptic potassium efflux, and reduce presynaptic calcium influx.
• Uses: Analgesia, cough suppression, diarrhea treatment, acute pulmonary edema, anesthesia adjuncts
• Specific Drugs: Morphine, codeine.

Test your knowledge on pharmacology with this quiz focused on antibiotics and antiparasitic drugs. Explore drug mechanisms, side effects, and recommended treatments in various infections, including lymphatic filariasis, tapeworms, and gonorrhea. This quiz is perfect for students and professionals in the medical field.