Classification of Beta Lactam Antibiotics and Mechanism of Action of Benzyl Penicillin

β-lactam antibiotics (beta-lactam antibiotics) are a broad category of antibiotics. They contain all the antibiotic agents which have a β-lactam ring in their molecular structures. For example, all penicillin derivatives like penams and cephalosporins, carbapenems and monobactams. β-lactam antibiotics work by inhibiting the cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics. Bacteria often develop resistance to β-lactam antibiotics by synthesizing a β-lactamase, an enzyme that attacks the β-lactam ring. To overcome this resistance, β-lactam antibiotics are often given with β-lactamase inhibitors such as clavulanic acid. Classification and Sub-Types of Beta-Lactam Antibiotics 1. Penams - 1.1.1 β-Lactamase-sensitive 1.1.2 β-Lactamase-resistant 1.3.1 Carboxypenicillins 1.3.2 Ureidopenicillins 2. Cephems - 2.2.1 With anti-Haemophilus activity 2.2.2 With anti-anaerobic activity 3. Carbapenems 4. Monobactams 5. β-Lactamase inhibitors Mechanism of Action of Benzyl Penicillin Benzyl penicillin is also known as Penicillin G. It is given typically by injection parenterally as it bypasses the intestines for the simple reason that it is unstable in the acidic stomach. 6- aminopenicillanic acid Penicilloic acid Route of elimination - Penicillin G is eliminated by the kidneys. Non-renal clearance includes hepatic metabolism and biliary excretion. Impact Ratio - Normal renal function is around 10 minutes. Clearance is 560 ml/ minute. Toxicity - Oral LD50 is 8900 mk/kg. Organisms that are affected by it - Enteric bacteria and other eubacteria Therapeutic Uses Benzyl Penicillin is given therapeutically for:- • Cellulitis • Infective Endocarditis • Meningitis • Aspiration pneumonia • Lung abscess • Community-acquired pneumonia • Syphilis • Septicemia in children • Septic Arthritis • Gangrene • Diphtheria As far as the antimicrobial potency of benzyl penicillin is concerned, it is effective against all gram-positive organisms – for example, Neisseria Gonorrhea. Adverse Effects of Benzyl Penicillin Common adverse reactions for benzyl penicillin and β-lactam antibiotics include diarrhea, nausea, rash, urticaria and candidiasis. Frequent ADRs include fever, vomiting, dermatitis and angio-edema. Pain and inflammation at the injection site is also common for parenterally administered β-lactam antibiotics.