Quiz 48: Antibiotics Affecting Bacterial Protein Synthesis


Alcohol is mainly absorbed from the stomach and decreases gastric emptying. So, the alcohol increases elimination half-life of erythromycin due to the decreased gastric emptying. This also reduces the blood concentration of the drug, which may fail to produce the required therapeutic response. Chronic alcohol ingestion causes decreased liver functioning, thereby the decreased metabolism of the drug. In patients with decreased liver functioning, erythromycin may cause impaired hearing, vertigo and dizziness.

Warfarin (brand name, Coumadin) is an anticoagulant used to prevent the formation of blood clots (to prevent thrombosis). It undergoes metabolism by the liver cytochromeP450 enzymes. Macrolides (Eg: clarithromycin, azithromycin) are the bacteriostatic drugs that act by inhibiting the protein synthesis. These drug are the potent inhibitors of cytochrome P450 enzymes, which increase the plasma concentration of warfarin. Increased warfarin concentration further increase the risk of bleeding. Thus, the plasma levels of warfarin must be regularly monitored when given along with the macrolides.

Pneumonia is a condition of pulmonary inflammation, which mainly affects the alveoli. The causes of pneumonia may vary from person to person because many of the microbes such as bacteria and viruses, some of the drugs, and genetic inheritance can cause pneumonia. The symptoms of pneumonia include the chest pain, difficulty in breathing, cough with phlegm and fever. The bacterial capsules such as capsules of klebsiella pneumonia and streptococcus pneumoniae (both can cause pneumonia) secrete a type of glycocalyx, the capsules make these organisms resistant towards a variety of chemical disinfectant treatments, antibiotics such as beta lactams and phagocytosis. Drug resistant pneumococcal species (DRPS) also do not respond to regular antibiotic treatment. Thus, the patient did not respond to the initial antibiotic therapy. Certain drugs such as ceftriaxone are used for the treatment of pneumonia.

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