Pharmacology Practice Flashcards: Antimicrobial Drugs

A collection of vocabulary-style flashcards covering antimicrobial drugs, their mechanisms of action, adverse effects, and therapeutic uses as discussed in Professor Buster's and Dr. Priyanka Sachdev's lecture notes.

Minimum inhibitory concentration (MIC)

The lowest concentration of antibiotic which prevents visible growth of a bacterium.

Maximum bactericidal concentration (MBC)

The concentration of an antibiotic which kills $99.9\%$ of bacteria.

Bacteriostatic drugs

Antimicrobials that inhibit bacterial growth without necessarily killing the organism, such as Tetracyclines, Chloramphenicol, and Macrolides.

Bactericidal drugs

Antimicrobials that actively kill bacteria, including Aminoglycosides, Beta-lactams, and Fluoroquinolones.

Tetracyclines Mechanism of Action

Inhibition of protein synthesis by binding to $30S$ ribosomes and interfering with the attachment of new aminoacyl t-RNA to the acceptor (A) site.

Fanconi syndrome (outdated Tetracyclines)

A reversible condition involving damage to proximal tubules caused by degraded tetracycline products like epitetracycline and anhydrotetracycline.

Demeclocycline

A tetracycline that antagonizes ADH action and is used to treat conditions where water reabsorption needs to be reduced, though it can cause diabetes insipidus.

Nitrobenzene moiety

The chemical structure responsible for the antibacterial activity of Chloramphenicol.

Gray baby syndrome

A potentially fatal condition in premature neonates caused by high doses of Chloramphenicol due to their inability to conjugate the drug with glucuronic acid and excrete it.

Aminoglycosides Mechanism of Action

Bactericidal protein synthesis inhibitors that bind to the $30S$ ribosomal subunit, freeze initiation, and cause misreading of the mRNA code.

Ototoxicity

A major adverse effect of Aminoglycosides involving progressive destruction of sensory cells in the cochlea and vestibule, which can lead to permanent deafness.

Nephrotoxicity (Aminoglycosides)

Acute tubular necrosis caused by the drug binding to phospholipids in the renal brush border; it is typically reversible upon discontinuation.

Spectinomycin

A drug with a mechanism similar to aminoglycosides used specifically to treat gonorrhea in patients allergic to penicillin.

Azithromycin Mechanism of Action

A macrolide that binds to the $50S$ ribosomal subunit and inhibits the translocation step of bacterial protein synthesis.

Motilin receptor agonist

A property of Erythromycin that induces gastric contractions and promotes intestinal motility, often causing epigastric pain.

Sulfonamides Mechanism of Action

Structural analogues of PABA that competitively inhibit folate synthase, thereby preventing the synthesis of folic acid in bacteria.

Kernicterus

A condition where sulfonamides displace bilirubin from protein-binding sites, allowing it to cross the blood-brain barrier and deposit in the basal ganglia of neonates.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

A genetic condition where exposure to pro-oxidant drugs like sulfonamides, dapsone, or isoniazid causes intravascular hemolysis due to inadequate NADPH production.

Cotrimoxazole

A synergistically bactericidal combination of Sulfamethoxazole and Trimethoprim in a $5:1$ ratio.

Fluoroquinolones Mechanism of Action

Inhibition of bacterial DNA gyrase in gram-negative bacteria and Topoisomerase IV in gram-positive bacteria to prevent DNA replication.

Beta-lactam Mechanism of Action

Inhibition of transpeptidase enzymes to prevent cross-linking of peptidoglycan residues, leading to a cell-wall deficient form that undergoes bacterial lysis.

Penicillin Binding Proteins (PBPs)

The target site of penicillin; alterations in these proteins (e.g., PBP-2a) lead to resistance in organisms like MRSA.

Jarisch-Herxheimer reaction

A reaction seen in syphilitic patients after penicillin injection, caused by the sudden release of spirochetal lytic products, resulting in fever and shivering.

Clavulanic acid

A 'suicide' inhibitor obtained from Streptomyces clavuligerus that protects beta-lactam antibiotics from enzymatic inactivation by binding to beta-lactamases.

Cefazolin

A first-generation cephalosporin used as the drug of choice for surgical prophylaxis.

Ceftriaxone

A third-generation cephalosporin that is excreted mainly in bile and is a drug of choice for typhoid, gonorrhea, and bacterial meningitis.

Imipenem

A carbapenem with a wide spectrum of activity that must be combined with cilastatin to prevent inactivation by renal dehydropeptidase I.

Isoniazid (H) Mechanism of Action

An antitubercular prodrug activated by catalase-peroxidase (KatG) that inhibits the synthesis of mycolic acids.

Rifampin (R) Mechanism of Action

A potent bactericidal antitubercular drug that inhibits DNA-dependent RNA polymerase (rpoB gene product) to interrupt RNA synthesis.

Pyrazinamide (Z) Toxicity

The most hepatotoxic first-line antitubercular drug, also known to cause hyperuricaemia and arthralgia.

Ethambutol (E) Mechanism of Action

A bacteriostatic antitubercular drug that inhibits arabinosyl transferase to prevent the synthesis of the mycobacterial cell wall.

Optic neuritis

A dose-related adverse effect of Ethambutol characterized by decreased visual acuity and the inability to differentiate red from green.

DOTS (Directly Observed Therapy - short course)

The WHO-recommended strategy for tuberculosis control where health workers supervise patients swallowing their daily medication.

Dapsone (DDS)

The simplest and cheapest antileprotic drug; it acts as a competitive inhibitor of folate synthase, similar to sulfonamides.

Clofazimine

A phenazine dye used in leprosy treatment that exerts anti-inflammatory effects and can cause reddish-black skin discoloration.