Quinolone Drug Interactions

Quinolone Drug Interactions

• Dairy products, antacids, iron, zinc, or calcium supplements may interfere with the absorption of quinolones, so they should not be taken within 2 hours of a quinolone dose.
• Quinolones may increase the effects of caffeine, so caffeine intake may need to be reduced.
• Ciprofloxacin is an inhibitor of CYP3A4.
• Gatifloxacin and moxifloxacin do not appear to interact with hepatically metabolized drugs (e.g., theophylline, caffeine, warfarin).

Folate Inhibitors

• Trimethoprim and sulfamethoxazole are used in combination for synergistic effect.
• Adverse drug reactions (ADRs) of folate inhibitors include fever, nausea, vomiting, diarrhea, anorexia, rash, itch, sore mouth, hyperkalaemia, and thrombocytopenia.
• Rare ADRs include megaloblastic anaemia, methaemoglobinaemia, erythema, hypoglycaemia, hepatitis, crystalluria, urinary obstruction with anuria/oliguria, lowered mental acuity, depression, tremor, ataxia, Clostridium difficile-associated disease, and aseptic meningitis.

Sulfonamide Allergy

• Sulfonamide allergy, also known as "sulfur allergy," is caused by the arylamine-sulfonamide functional groups.
• Symptoms include fever, dyspnoea, cough, rash, eosinophilia, anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis, serum sickness-like syndrome, lupus-like syndrome, pneumonitis, hepatitis, interstitial nephritis, systemic vasculitis, and pancytopenia.
• Cross-sensitivity between sulfonamides and related drugs (e.g., sulfonylureas, thiazides diuretics, frusemide, celecoxib) may occur.

Folate Inhibitor Precautions

• G6PD deficiency increases the risk of haemolysis with sulfonamides.
• Slow acetylator phenotype increases the risk of adverse effects with sulfonamides.
• Low urine pH increases the risk of crystalluria, and sulfamethoxazole is poorly soluble at low pH.
• Drugs that cause potassium retention (e.g., ACE inhibitors) may contribute to hyperkalaemia with TMP.
• Renal impairment increases the risk of hyperkalaemia or hypoglycaemia, and the dose of sulfamethoxazole should be reduced.
• Folate inhibitors are contraindicated in preterm infants and neonates.

Tetracycline Precautions

• Tetracyclines are contraindicated in children and pregnant women due to the risk of tooth discoloration and bone growth inhibition.
• Tetracyclines may increase the risk of benign intracranial hypertension with oral retinoids (e.g., isotretinoin, acitretin).
• Hepatic impairment increases the risk of hepatotoxicity with tetracyclines.
• Doxycycline and minocycline can be used with dose adjustment in renal impairment.

Aminoglycoside Precautions

• Aminoglycoside allergy, ototoxicity, and nephrotoxicity are increased in patients with a history of treatment with ototoxic or nephrotoxic drugs.
• Neuromuscular disease (e.g., myasthenia gravis) increases the risk of neuromuscular blockade with aminoglycosides.
• Hypocalcaemia, hypermagnesaemia, general anaesthesia, and large transfusions of citrated blood increase the risk of aminoglycoside toxicity.
• Dehydration increases the risk of toxicity, and renal impairment increases the risk of nephrotoxicity and ototoxicity.

Quinolone Precautions

• Quinolones are contraindicated in children and adolescents due to the risk of arthropathy.
• Quinolones may increase the risk of seizures in patients with epilepsy or a history of CNS disorders.
• Treatment with bupropion should be avoided due to the increased risk of seizures.
• Myasthenia gravis increases the risk of exacerbation with quinolones.
• G6PD deficiency increases the risk of haemolytic anaemia with quinolones.
• Prior or concomitant use of corticosteroids increases the risk of tendon damage with quinolones.

Quinolone ADRs

• Common ADRs include rash, itch, nausea, vomiting, diarrhea, abdominal pain, headache, dizziness, insomnia, depression, restlessness, tremors, arthralgia, arthritis, myalgia, tendonitis, crystalluria, and interstitial nephritis.
• Infrequent ADRs include hypoglycaemia, hyperglycaemia, blood dyscrasias, seizures, psychotic reactions, angioedema, anaphylaxis, pseudomembranous colitis, tendon rupture, Stevens-Johnson syndrome, hepatitis, peripheral neuropathy, and others.

This quiz covers the interactions of quinolone drugs with other substances, including dairy products, antacids, and caffeine. It also discusses the effects of quinolones on hepatically metabolized drugs.