Raxar

Raxar hydrochloride (Raxar®, Glaxo Wellcome) is an oral broad-spectrum quinoline antibacterial agent used to treat bacterial infections. Raxar was withdrawn in the United States due to its side effect of lengthening the QT interval on the electrocardiogram, leading to cardiac events and sudden death. .
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Raxar - Pharmacology:

Raxar exerts its antibacterial activity by inhibiting bacterial topoisomerase II (DNA gyrase) and topoisomerase IV, essential enzymes for duplication, transcription, and repair of bacterial DNA.

Raxar for patients

Patients should be advised:

  • that grepafloxacin may be taken with or without meals.
  • that grepafloxacin increases the effects of theophylline, and to advise their physician immediately if they are taking theophylline.
  • that multivitamins (containing iron or zinc), antacids, (containing magnesium, calcium, or aluminum), sucralfate, or VIDEX (didanosine) chewable/buffered tablets or the pediatric powder for oral solution should not be taken within 4 hours before or 4 hours after taking grepafloxacin .
  • that grepafloxacin may increase the effects of other drugs metabolized by the liver, and to advise their physician of any of the drugs they are taking.
  • to drink fluids liberally.
  • that grepafloxacin may increase the effects of caffeine.
  • that grepafloxacin may be associated with hypersensitivity reactions, even following a single dose, and to discontinue the drug at the first sign of skin rash, hives, or other skin reactions, a rapid heartbeat, difficulty in swallowing or breathing, or any other symptom of an allergic reaction .
  • that grepafloxacin may cause dizziness and lightheadedness; therefore, patients should know how they react to this drug before they operate an automobile or machinery or engage in activities requiring mental alertness and coordination.
  • to discontinue treatment; rest and refrain from exercise; and to contact their physician immediately if they experience pain, inflammation or rupture of a tendon .
  • to avoid excessive sunlight or artificial ultraviolet light while taking grepafloxacin and to discontinue therapy if phototoxicity (e.g., sunburn-like reaction or skin eruptions) occurs.

Raxar Interactions

Antacids, Sucralfate, Metal Cations, Multivitamins

Quinolones form chelates with alkaline earth and transition metal cations. Administration of quinolones with antacids containing aluminum, magnesium, or calcium, with sucralfate, with metal cations such as iron, or with multivitamins containing iron or zinc, or with formulations containing divalent and trivalent cations such as VIDEX (didanosine) chewable/buffered tablets or the pediatric powder for oral solution, may substantially interfere with the absorption of quinolones, resulting in systemic concentrations considerably lower than desired. These agents should not be taken within 4 hours before or 4 hours after grepafloxacin administration.

Caffeine Theobromine

Raxar, like other quinolones, may inhibit the metabolism of caffeine and theobromine. These stimulants are commonly found in coffee and tea, respectively. In some patients, this may lead to reduced clearance, prolongation of plasma half-life, and enhanced effects of caffeine and theobromine.

Theophylline

Raxar is a competitive inhibitor of the metabolism of theophylline. Serum theophylline concentrations increase when grepafloxacin is initiated in a patient maintained on theophylline. When initiating a multi-day course of grepafloxacin in a patient maintained on theophylline, the theophylline maintenance dose should be halved for the period of concurrent use of grepafloxacin and monitoring of serum theophylline concentrations should be initiated as a guide to further dosage adjustments.

Warfarin

In subjects receiving warfarin, no significant change in clotting time was observed when grepafloxacin was coadministered. However, because some quinolones have been reported to enhance the effects of warfarin or its derivatives, prothrombin time or other suitable anticoagulation test should be monitored closely if a quinolone antimicrobial is administered with warfarin or its derivatives.

Drugs Metabolized by Cytochrome P450 Enzymes

The drug interaction study evaluating the effect of grepafloxacin on theophylline indicates that grepafloxacin inhibits theophylline metabolism, which is mediated by CYP1A2. While no clinical studies have been conducted to evaluate the effect of grepafloxacin on the metabolism of C.P.A. substrates, in vitro data suggest similar effects of grepafloxacin in CYP3A4 mediated metabolism and theophylline metabolism. In addition, other quinolones have been reported to decrease the CYP3A4-mediated metabolism of cyclosporine. Other drugs metabolized by C.P.A. include terfenadine, astemizole, cisapride, midazolam, and triazolam. The clinical relevance of the potential effect of grepafloxacin on the metabolism of C.P.A. substrates is not known. Patients receiving concurrent administration of substrates of C.P.A. were not excluded from clinical trials of grepafloxacin.

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

The concomitant administration of a nonsteroidal anti inflammatory drug with a quinolone may increase the risks of CNS stimulation and convulsions.

Antidiabetic Agents

Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with quinolones and an antidiabetic agent. Therefore, careful monitoring of blood glucose is recommended when these agents are coadministered.

Raxar Contraindications

RAXAR Tablets are contraindicated in persons with a history of hypersensitivity to grepafloxacin or other members of the quinolone class of antimicrobial agents. RAXAR Tablets are contraindicated in patients with hepatic failure. Because prolongation of the QTc interval has been observed in healthy volunteers receiving RAXAR, RAXAR Tablets are contraindicated in patients with known QTc prolongation. RAXAR Tablets are also contraindicated in patients being treated concomitantly with medications known to produce an increase in the QTc interval and/or torsade de pointes (e.g., terfenadine) unless appropriate cardiac monitoring can be assured (e.g., in hospitalized patients).

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Raxar see also