Quzyttir
Quzyttir
Generic Name
Quzyttir
Mechanism
Quzyttir inhibits bacterial DNA replication by binding competitively to the active sites of
•
• DNA gyrase (GyrA), preventing supercoiling of DNA necessary for transcription and replication.
• Topoisomerase IV (ParC), disrupting segregation of newly synthesized chromosomes.
This dual inhibition results in rapid bacterial killing and reduces the likelihood of resistance development.
Pharmacokinetics
- Absorption: Oral bioavailability 70 % (peak plasma concentration in 1–2 h).
- Distribution: Volume of distribution 2.5 L/kg. Highly protein‑bound (≈85 %).
- Metabolism: Primarily hepatic via CYP3A4 and UGT1A9; minor phase II glucuronidation.
- Elimination: 60 % renal (urine), 30 % fecal.
- Half‑life: 7.5 h (oral), 8 h (IV).
- Steady‑state: Achieved after 1 day of once‑daily dosing.
Indications
- Acute bacterial lower respiratory tract infections (community‑acquired pneumonia)
- Uncomplicated urinary tract infections (cystitis)
- Complicated intra‑abdominal infections (when susceptibility patterns support use)
- Skin and soft tissue infections caused by *Staphylococcus aureus* and *Enterococcus* spp.
- Treatment of *Pseudomonas aeruginosa* bacteremia in select cases.
Contraindications
- Severe hepatic impairment (Child‑Pugh C) – significant reduction in clearance.
- Pregnancy (Category C) – animal studies show no teratogenic effect, but data in humans are limited.
- Lactation – excretion into breast milk; infant exposure not studied.
- QT Prolongation – caution when combined with other QT‑prolonging drugs (e.g., azithromycin, amiodarone).
- Hypersensitivity to quinolones – cross‑reactivity risk.
Dosing
| Population | Oral | Intravenous |
| Adults | 500 mg q12 h or 400 mg q24 h (extended release) | 400 mg q24 h (in 0.9 % NaCl, 30 min infusion) |
| Elderly (≥65 y) | 250 mg q24 h (if creatinine clearance 30‑59 mL/min) | 250 mg q24 h (if CrCl 30‑59 mL/min) |
| Renal impairment (CrCl ≥30 mL/min) | 500 mg q12 h (adjust on CrCl) | 200 mg q24 h (standard) |
| Pediatric <12 y | Not approved; use weight‑based 6.5 mg/kg q12 h (if safe) | 3.3 mg/kg q24 h (if safe) |
• Administration Notes: Take with a full glass of water; may cause mild GI upset if taken on an empty stomach. Avoid concurrent administration with dairy products or antacids (chelate metal ions).
Monitoring
- Baseline ECG if QT‑prolonging medications are co‑administered.
- Renal function (serum creatinine, GFR) every 3 days during the first week.
- Liver enzymes (ALT, AST) monthly if hepatic disease suspected.
- Signs of tendonitis: patient education on immediate reporting of tendon pain or swelling.
- Blood glucose for patients at risk of dysglycemia.
Clinical Pearls
- Synergy with β‑lactams: In mixed flora infections, a combination of *Quzyttir* and a β‑lactam (e.g., ampicillin) can reduce resistance emergence.
- Avoid in the first trimester: Though animal studies show no teratogenicity, human data are scarce; consider safer alternatives until more evidence emerges.
- Photosensitivity risk: Encourage patients to wear broad‑spectrum SPF 30+ sunscreen and limit sun exposure during therapy.
- Tendon rupture risk mitigation: Limit use with concomitant corticosteroids or in patients >75 y; advise avoidance of strenuous exercise during treatment.
- Renal dose adjustment: Use CrCl or estimated GFR; for CrCl <30 mL/min, consider a 30 % dose reduction or switch to an alternative agent.
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• Key Pharmacology Terms: Quily (quinolone), DNA gyrase, topoisomerase IV, QT prolongation, tendinopathy, pharmacokinetic absorption, renal clearance, liver metabolism.