Drug Study: Xtenda

Generic Name: Ceftriaxone

Dosage: 250mg/ 500mg/ 1 g powder for injection (I.M./ I.V.)

Category: Antibacterial

Formulation:

Each vial contains Ceftriaxone sodium USP (sterile) equivalent to anhydrous Ceftriaxone…250mg, 500mg, 1g

Description:
Ceftriaxone is a white to yellowish-orange crystalline powder which is readily soluble in water, sparingly soluble in methanol and very slightly soluble in ethanol. The pH of a 1% aqueous solution is approximately 6.7. The color of Ceftriazone solution ranges from light yellow to amber, depending on the length of storage, concentration and diluent used.

Chemically, Ceftriaxone sodium USP is a 5-thia-1-azabicycloi [4.2.0]oct-2-ene2-carboxyalic acid,7 [[2-(2-Amino-4-thiazolyl)methyloxime) acetyl]amino] 8-ixi-3-[[(1,2,5,6-tetrahydro-2-methyl-5,6-dioxo-as-triazin-3-yl)thio]methyl]-,disodium salt trisesquihydrate [6R-[6a,7b(z)]]. Its empirical formula is C18H16N8Na2O7S3 3.5H2o with molecular weight of 662.0.

Mechanism of Action:
Ceftriaxone like other cephalosphorin and penicillins, kills bacteria by inhibiting mucopepide synthesis and hence interfere with the synthesis of the bacterial cell wall. Ceftriaxone binds with high affinity to penicillin binding proteins in the bacterial cell wall, thus interfering with peptidolycan synthesis. Peptidoglycan is a hetropolymeric structure that provides a cell with mechanical stability. The final stage in the synthesis of peptidoclycan involves a completion of the cross linking and the terminal glycine residue of the pentaglycine bridge is linked to the fourth residue of the penta-petide. (D-alanine). The transpeptidase enzyme that performs this step is inhibited by cephalosphorins and penicillins. As a result the bacterial cell wall is weakened and the cell swell and then ruptures. Ceftriaxone is bactericidal against a broad spectrum of bacterial at easily achievable plasma concentrations.

Ceftriaxone is a third generation cephalosphorin which has a broad spectrum of activity against aerobic Gram positive and Gram negative organisms. Sensitive organisms are generally killed by a concentration of Ceftriaxone of 8mg/l or less while resistant organisms can survive concentrations of 64mg/l.

Pharmacokinetics:
Ceftriaxone is administered as intravenous and intramuscular injectin. The mean elimination half-life in healthy adults is about 6-9 hours and is thus much longer than any other Cephalosporins or cephamycins. The half-life does not alter with changes in the route of administration and was only slightly to moderately affected in patients with decreased renal function and relatively normal non renal elimination but was increased in neonates and in patients over 75 years of age.

Ceftriaxone was completely absorbed following IM administration with mean maximum plasma concentrations occurring between 2 and 3 hours post dosing. Multiple IV or IM doses ranging from 0.5 to 2 gs at 12- to 24- hour intervals resulted in 15 to 36% accumulation of ceftriaxone above single dose values.

33% to 67% of a ceftriaxone was excreted in the urine as unchanged drug and the reminder was secreted in the bile and ultimately found in the feces as microbiologically inactive compounds. After a 1g Iv dose, average concentrations of ceftriaxone, determined from 1 to 3 hours after dosing, were 581 mcg/mL in the gallbladder bile, 788 mcg/mL in the common duct bile, 898 mcg/ml in the cystic duct bile , 78.2 mcg/g in the gallbladder wall and 62.1mcg/mL in the concurrent plasma.

The drug is highly protein bound (95%), demonstrating distinctly non-linear concentration-dependent binding, with 5% free drug at levels <70 mg/l with this fraction increased to 16% at 300 mg/, 26.5% at 500mg/l and 42% at 600 mg/l. This, however has little clinical reference.

30 minutes after infusions of 0.5, 1.0 and 2.0g, mean peak plasma concentrations were 82,151 and 257mg/l respectively. 2 hours after intramuscular injection, mean peak plasma concentrations were around half of those after intravenous administration of an equivalent dose.

Indications:

Lower respiratory tract infections
Acute bacterial otitis media
Skin and skin structure infections
Urinary tract infections
Uncomplicated gonorrhea
Pelvic inflammatory disease
Bacterial septicemia
Bone and joint infections
Intra-abdominal infections
Meningitis
Surgical prophylaxis


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