Zyvox

ZYVOX- linezolid tablet, film coated
Cardinal Health


3
MDRSP refers to isolates resistant to two or more of the following antibiotics: penicillin, second-generation cephalosporins, macrolides, tetracycline, and trimethoprim/sulfamethoxazole.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of ZYVOX formulations and other antibacterial drugs, ZYVOX should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.

DESCRIPTION

ZYVOX I.V. Injection, ZYVOX Tablets, and ZYVOX for Oral Suspension contain linezolid, which is a synthetic antibacterial agent of the oxazolidinone class. The chemical name for linezolid is (S)-N-[[3-[3-Fluoro-4-(4-morpholinyl)phenyl]-2-oxo-5-oxazolidinyl]methyl]-acetamide.

The empirical formula is C16 H20 FN3 O4 . Its molecular weight is 337.35, and its chemical structure is represented below:

Formula
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ZYVOX I.V. Injection is supplied as a ready-to-use sterile isotonic solution for intravenous infusion. Each mL contains 2 mg of linezolid. Inactive ingredients are sodium citrate, citric acid, and dextrose in an aqueous vehicle for intravenous administration. The sodium (Na+) content is 0.38 mg/mL (5 mEq per 300-mL bag; 3.3 mEq per 200-mL bag; and 1.7 mEq per 100-mL bag).

ZYVOX Tablets for oral administration contain 400 mg or 600 mg linezolid as film-coated compressed tablets. Inactive ingredients are corn starch, microcrystalline cellulose, hydroxypropylcellulose, sodium starch glycolate, magnesium stearate, hypromellose, polyethylene glycol, titanium dioxide, and carnauba wax. The sodium (Na+) content is 1.95 mg per 400-mg tablet and 2.92 mg per 600-mg tablet (0.1 mEq per tablet, regardless of strength).

ZYVOX for Oral Suspension is supplied as an orange-flavored granule/powder for constitution into a suspension for oral administration. Following constitution, each 5 mL contains 100 mg of linezolid. Inactive ingredients are sucrose, citric acid, sodium citrate, microcrystalline cellulose and carboxymethylcellulose sodium, aspartame, xanthan gum, mannitol, sodium benzoate, colloidal silicon dioxide, sodium chloride, and flavors (see PRECAUTIONS, Information for Patients). The sodium (Na+) content is 8.52 mg per 5 mL (0.4 mEq per 5 mL).

CLINICAL PHARMACOLOGY

Pharmacokinetics

The mean pharmacokinetic parameters of linezolid in adults after single and multiple oral and intravenous (IV) doses are summarized in Table 1. Plasma concentrations of linezolid at steady-state after oral doses of 600 mg given every 12 hours (q12h) are shown in Figure 1.

Table 1. Mean (Standard Deviation) Pharmacokinetic Parameters of Linezolid in Adults
Dose of LinezolidCmax µg/mLCmin µg/mLTmax hrsAUC *µg ∙ h/mLt1/2 hrsCLmL/min
Cmax = Maximum plasma concentration; Cmin = Minimum plasma concentration; Tmax = Time to Cmax ; AUC = Area under concentration-time curve; t1/2 = Elimination half-life; CL = Systemic clearance
*
AUC for single dose = AUC0–∞ ; for multiple-dose = AUC0–τ
Data dose-normalized from 375 mg
Data dose-normalized from 625 mg, IV dose was given as 0.5-hour infusion.
400 mg tablet single dose every 12 hours8.10(1.83)11.00(4.37)—3.08(2.25)1.52(1.01)1.12(0.47)55.10(25.00)73.40(33.50)5.20(1.50)4.69(1.70)146(67)110(49)
600 mg tablet single dose every 12 hours12.70(3.96)21.20(5.78)—6.15(2.94)1.28(0.66)1.03(0.62)91.40(39.30)138.00(42.10)4.26(1.65)5.40(2.06)127(48)80(29)
600 mg IV injection single dose every 12 hours12.90(1.60)15.10(2.52)—3.68(2.36)0.50(0.10)0.51(0.03)80.20(33.30)89.70(31.00)4.40(2.40)4.80(1.70)138(39)123(40)
600 mg oral suspension single dose11.00(2.76)0.97(0.88)80.80(35.10)4.60(1.71)141(45)
Graph
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Figure 1. Plasma Concentrations of Linezolid in Adults at Steady-State Following Oral Dosing Every 12 Hours (Mean ± Standard Deviation, n=16)

Absorption

Linezolid is rapidly and extensively absorbed after oral dosing. Maximum plasma concentrations are reached approximately 1 to 2 hours after dosing, and the absolute bioavailability is approximately 100%. Therefore, linezolid may be given orally or intravenously without dose adjustment.

Linezolid may be administered without regard to the timing of meals. The time to reach the maximum concentration is delayed from 1.5 hours to 2.2 hours and Cmax is decreased by about 17% when high fat food is given with linezolid. However, the total exposure measured as AUC0-∞ values is similar under both conditions.

Distribution

Animal and human pharmacokinetic studies have demonstrated that linezolid readily distributes to well-perfused tissues. The plasma protein binding of linezolid is approximately 31% and is concentration-independent. The volume of distribution of linezolid at steady-state averaged 40 to 50 liters in healthy adult volunteers.

Linezolid concentrations have been determined in various fluids from a limited number of subjects in Phase 1 volunteer studies following multiple dosing of linezolid. The ratio of linezolid in saliva relative to plasma was 1.2 to 1 and for sweat relative to plasma was 0.55 to 1.

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