Pharmacology
Antimicrobials and Chemotherapy
Antimicrobial drugs for MBBS and NEET-PG: beta-lactams, aminoglycosides, antitubercular, antifungal, antimalarial and antiretroviral therapy, mapped to NMC codes.
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Antimicrobials and Chemotherapy
Antimicrobial drugs for MBBS and NEET-PG: beta-lactams, aminoglycosides, antitubercular, antifungal, antimalarial and antiretroviral therapy, mapped to NMC codes.
This chapter covers the antimicrobial agents used against bacteria, mycobacteria, fungi, protozoa and viruses. It groups antibiotics by mechanism, sets out the key toxicities, and covers the principles of tuberculosis, malaria, fungal and antiretroviral therapy along with the drivers of antimicrobial resistance.
High-yield: Antimicrobials and Chemotherapy
- Beta-lactams such as penicillins and cephalosporins inhibit bacterial cell wall synthesis and are bactericidal.
- Aminoglycosides such as gentamicin inhibit protein synthesis and cause dose-related nephrotoxicity and ototoxicity.
- Macrolides such as erythromycin and clarithromycin inhibit protein synthesis and inhibit cytochrome enzymes, raising the levels of other drugs.
- Fluoroquinolones such as ciprofloxacin can cause tendon rupture and QT prolongation and are avoided in children and pregnancy.
- Vancomycin is used for methicillin-resistant Staphylococcus aureus and can cause red man syndrome if infused too fast.
- Tetracyclines are avoided in children and pregnancy because they stain developing teeth and affect bone growth.
- Rifampicin is a potent enzyme inducer that colours body fluids orange and is a cornerstone of tuberculosis therapy.
- Isoniazid can cause peripheral neuropathy prevented by pyridoxine and can cause hepatitis.
- Ethambutol causes reversible optic neuritis with loss of colour vision, requiring eye monitoring.
- Metronidazole treats anaerobic and protozoal infections and causes a disulfiram-like reaction with alcohol.
- Chloroquine is used in sensitive malaria and can cause retinopathy with long-term use.
- Amphotericin B is a potent antifungal that causes nephrotoxicity and infusion reactions.
- Aciclovir treats herpes infections by selective activation in infected cells, giving a wide safety margin.
- Antiretroviral therapy uses at least three drugs from different classes to suppress HIV and prevent resistance.
Antimicrobial toxicity flags
- **Aminoglycosides:** Nephrotoxicity and ototoxicity; monitor levels and renal function.
- **Antitubercular drugs:** Isoniazid neuropathy, rifampicin induction, ethambutol optic neuritis.
- **Metronidazole:** Disulfiram-like reaction with alcohol; anaerobes and protozoa.
- **Vancomycin:** For MRSA; red man syndrome with rapid infusion.
NMC competencies in this chapter
- **PH1.42:** General principles of antimicrobial therapy and resistance
- **PH1.43:** Beta-lactams and other cell wall inhibitors
- **PH1.44:** Protein synthesis inhibitors and other antibacterials
- **PH1.45:** Antitubercular and antileprotic drugs
- **PH1.46:** Antifungal and antiviral drugs
- **PH1.47:** Antimalarial and antiprotozoal drugs
- **PH1.48:** Anthelmintic drugs and antiretroviral therapy
Frequently Asked Questions
Why is pyridoxine given with isoniazid?
Isoniazid interferes with vitamin B6 metabolism and can cause peripheral neuropathy, which pyridoxine supplementation prevents.
Why avoid alcohol with metronidazole?
Metronidazole inhibits acetaldehyde breakdown, producing a disulfiram-like reaction with flushing, nausea and vomiting when alcohol is taken.
What causes red man syndrome?
Rapid infusion of vancomycin releases histamine, causing flushing of the upper body; slowing the infusion prevents it.
Why are tetracyclines avoided in children and pregnancy?
They bind to developing teeth and bone, causing permanent tooth discolouration and affecting bone growth in the fetus and young children.
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