Antimicrobial Agents (General considerations)

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Antimicrobial Agents (General considerations)
Prof. R. K. Dixit Pharmacology and
Therapeutics K.G.M.U. Lucknow dixitkumarrakesh_at_gma
il.com
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Objectives.

• Important drug interactions related to
  antimicrobials

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Important Drug Interactions of Antimicrobials
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Important Drug Interactions of Antimicrobials
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Important Drug Interactions of Antimicrobials
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Important Drug Interactions of Antimicrobials
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List of Important Interactions Related to
Antimicrobials
Sulphonamides Oral hypoglycaemics (Especially Sulphonylureas) Increased hypoglycemia
Oral anticoagulants Increased anticoagulation (Protein binding displacement)
Methotrexate (Inhibitor of Dihydrofolate Reducatase) Increased methotrexate toxicity (Folate deficiency)
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Fluoroquinolone Antacids (Al, Mg, Ca), Zinc, Iron, Sucralfate, Milk Reduced absorption of Fluoroquinolone
Theophylline Increased concentration due to decreased metabolism. (Least with Lome, Levo, Spar)
Warfarin (Oral anti-coagulant) Enhanced effect due to decreased metabolism (least with Levo, Spar)
Quinidine, Procainamide, Amidarone, Erythromycin, Cisapride, Astemizole, Terfenadine, Enhance Q-T interval leading to dangerous arrhythmia
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Ampicillin (Penicillin), (Cephalosporin) Contraceptive pills Failure of contraception (Inhibition of enterohepatic recirculation)
Tetracycline, Chloramphenicol, Erythromycin Antagonism of bactericidal action (Cidal with Static)
Aminoglycoside in same syringe Inactivation of both (Pharmaceutical)
Hydrocortisone Inactivation of penicillin (Pharmaceutical)
Allopurinol Increased incidence of non-urticarial maculo-papular rashes
Probenecid Decreases tubular secretion of penicillin and increases action (Pk)
Clavulanic acid, Sulbactam Inhibition of Betalactamase leading to better effect (Synergism)
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Cephaloridine Furosemide Increased nephrotoxicity
Rifampicin Warfarin and OCP Failure of anti-coagulation and contraception
Griseofulvin Cefoperazone, Cefotetan, Cefamandole Metronidazole (Good Chief Minister) Alcohol Disulfiram like syndrome (Aldehyde Syndrome)
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Nalidixic acid Oral anticoagulants Enhanced anticoagulation
Nitrofurantoin Nalidixic acid Antagonises action of nalidixic acid
Probenecid Reduced tubular secretion leading to decreased concentration in urine
Amphotericin-B Digitalis Amphotericin induced hypo-kalemia increases digitalis toxicity
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Erythromycin Theophylline, CarbamazepineStatins, Warfarin, Terfenadine, Inhibition of metabolism (Inhibit CYP3A4)
Terfenadine Q-T prolongation leading to life threatening ventricular arrhythmias
Linezolid MAO inhibitors Increased toxicity of MAO inhibitors (Linezolid is reversible inhibitor of MAO and may lead to cheese reaction with food containing tyramine and can precipitate Serotonin syndrome (confusion, hypertension, seizures, tachycardia and muscle rigidity)
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Streptogramins (Pristinamycin) Calcium channel blockers, Cyclosporine, Statins, Diazepam, Warfarin, Terfenadine, Cisapride Reduce liver metabolism of these drugs
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Aminoglycosides Furosemide, Ethacrynic acid Increased Ototoxicity
Skeletal muscle relaxants (curare like drugs) Enhanced and persistent neuromuscular blockade
Tetracyclines Contraceptive pills Failure of contraception
Antacids, Iron Milk , Food Decreased absorption due to Chelation
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Chloramphenicol Oral hypoglycemic Increased hypoglycemic effect (due to enzyme inhibition by Chloramphenicol)
Oral anti-coagulant Enhanced anticoagulant
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Ketoconazole Cisapride, Terfenadine, Astemizole, Quinidine, Warfarin, Cyclosporine Tacrolimus Statins Ketoconazole inhibits CYP3A4 leading to decreased metabolism and accumulation of other drug (Least with Fluconazole)
H2 blockers, PPI, Antacids Decreased absorption of Ketoconazole due to decreased gastric acidity
Amphotericin B Ketoconazole inhibits the synthesis of ergosterol and produces depletion of membrane ergosterol reducing the binding sites for Amphotericin B
Griseofulvin Other drug Inducer of microsomal enzymes
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