Penicillin and Its Adverse Reactions

Penicillin

• Penicillin V is absorbed better than Penicillin G and is less affected by food.
• Penicillin V is less affected by disturbances in the gastrointestinal tract.
• Penicillin V is used to treat respiratory tract infections, urinary tract infections, dental infections, and β-hemolytic Streptococcal pharyngitis.
• Benzathine Ampicillin is used to treat Staph.Pseudomonas infections, shigellosis, and syphilis.
• Penicillin is used for prophylaxis against infective endocarditis.

Adverse Reactions of Penicillin

• Hypersensitivity: Most common drug implicated in drug allergies, can cause rash, itching, urticaria, fever, and anaphylaxis.
• More common with parenteral administration, Highest with procaine penicillin
• Skin sensitivity test (A scratch test or intradermal test) should be done before parenteral administration.
• Thrombophlebitis of injected vein.
• Diarrhea with ampicillin.
• Seizures: especially in renal impairment.

Drug Interactions of Penicillin

• Synergism: Penicillin + Aminoglycosides; both drugs shouldn’t be mixed in the same syringe. Penicillin facilitates the entry of aminoglycosides by inhibiting the cell wall synthesis.
• Antagonism: Penicillin + Tetracyclines: Bacteriostatic (Tetracyclines) with bactericidal effect of penicillin.
• Potentiation: Penicillin + Probenecid: Probenecid competes with penicillin on the excretory pathway leading to increased plasma concentration of penicillins.
• Penicillins decrease the effect of oral contraceptive pills.

Vancomycin

• Poorly absorbed orally.
• Administered intravenously as an infusion over 1 hour.
• Used to treat MRSA infections (e.g., osteomyelitis, pneumonia, endocarditis).
• Used orally to treat Pseudomembranous colitis, although metronidazole is preferred due to less resistance.
• Adverse effects: Infusion-related reactions, Red-man syndrome.

Fosfomycin

• Used to treat urinary tract infection and cystitis in women.
• Safe during pregnancy.

Teicoplanin

• Used to treat serious staphylococcal and streptococcal infections.
• Has no gram-negative activity.
• Long duration of action.
• Indicated for MRSA infection, multi-resistant gram-positive infections (e.g., Enterococcus faecium), and serious gram-positive infections in patients allergic to other antimicrobials.

Beta-Lactamase Inhibitors

• Beta-Lactamase enzymes are produced by bacteria that inactivate beta-lactam antibiotics.
• Beta-lactamase inhibitors include clavulanic acid, sulbactam, and tazobactam.
• Examples:
  • Amoxicillin + Clavulanic Acid
  • Ampicillin + Sulbactam
  • Piperacillin + Tazobactam
• Hepatotoxicity has been reported with the use of amoxicillin + clavulanic acid but not with amoxicillin alone.

Cephalosporins

• Cephalosporins are grouped into generations based on their development and clinical uses.
• Later generations have greater gram-negative activity and are more resistant to β-lactamase.
• First Generation: Cephradine, Cephalexin, Cefazolin
  • Uses: Respiratory tract infections, urinary tract infections, surgical prophylaxis (Cefazolin).
• Second Generation: Cefaclor, Cefamandole, Cefuroxime.
  • Uses: Respiratory tract infections, urinary tract infections, Meningitis (Cefazolin).
• Third Generation:
  • Parenteral: Cefotaxime, Ceftazidime, Ceftriaxone, Cefoperazone.
  • Oral: Cefixime, Cefdinir.
  • Ceftriaxone passes the blood-brain barrier and undergoes biliary excretion, making it safe for renal excretion.
• Fourth Generation: Cefepime.
  • Wider spectrum of activity, including Pseudomonas aeruginosa.

Pharmacokinetics of Cephalosporins

• Cefotaxime, ceftazidime, and ceftriaxone pass the blood-brain barrier.

This quiz covers essential information regarding Penicillin, including its absorption, uses in treating various infections, and common adverse reactions. It also highlights drug interactions and precautions necessary for safe administration. Test your knowledge on this crucial antibiotic and its implications.