Colistimethate

COLISTIMETHATE- colistimethate injection
Xellia Pharmaceuticals ApS

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

FOR INTRAMUSCULAR AND INTRAVENOUS USE

DESCRIPTION

Colistimethate for Injection, USP is a sterile parenteral antibiotic product which, when reconstituted (see Reconstitution), is suitable for intramuscular or intravenous administration.

Each vial contains colistimethate sodium or pentasodium colistinmethanesulfonate (150 mg colistin base activity).

Colistimethate sodium is a polypeptide antibiotic with an approximate molecular weight of 1750. The empirical formula is C58 H105 N16 Na5 O28 S5 and the structural formula is represented below:

structure
(click image for full-size original)

Dbu is 2,4-diaminobutanoic acid: R is 5-methylheptyl in colistin A and 5-methylhexyl in colistin B

CLINICAL PHARMACOLOGY

Typical serum and urine levels following a single 150 mg dose of Colistimethate for Injection, USP IM or IV in normal adult subjects are shown in Figure 1.

Figure 1
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Higher serum levels were obtained at 10 minutes following IV administration. Serum concentration declined with a half-life of 2 to 3 hours following either intravenous or intramuscular administration in adults and in the pediatric population, including premature infants.

Average urine levels ranged from about 270 mcg/mL at 2 hours to about 15 mcg/mL at 8 hours after intravenous administration and from 200 to about 25 mcg/mL during a similar period following intramuscular administration.

Microbiology

Colistimethate sodium is a surface active agent which penetrates into and disrupts the bacterial cell membrane. It has been shown to have bactericidal activity against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section:

Aerobic gram-negative microorganisms: Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa.

Susceptibility Tests

Colistimethate sodium is no longer listed as an antimicrobial for routine testing and reporting by clinical microbiology laboratories.

INDICATIONS AND USAGE

Colistimethate for Injection, USP is indicated for the treatment of acute or chronic infections due to sensitive strains of certain gram-negative bacilli. It is particularly indicated when the infection is caused by sensitive strains of Pseudomonas aeruginosa. This antibiotic is not indicated for infections due to Proteus or Neisseria. Colistimethate for Injection, USP has proven clinically effective in treatment of infections due to the following gram-negative organisms: Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa.

Colistimethate for Injection, USP may be used to initiate therapy in serious infections that are suspected to be due to gram-negative organisms and in the treatment of infections due to susceptible gram-negative pathogenic bacilli.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of Colistimethate for Injection, USP and other antibacterial drugs, Colistimethate for Injection, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

CONTRAINDICATIONS

The use of Colistimethate for Injection, USP is contraindicated for patients with a history of sensitivity to the drug or any of its components.

WARNINGS

Maximum daily dose calculated from colistin base activity should not exceed 5 mg/kg/day with normal renal function.

Transient neurological disturbances may occur. These include circumoral paresthesia or numbness, tingling or formication of the extremities, generalized pruritus, vertigo, dizziness, and slurring of speech. For these reasons, patients should be warned not to drive vehicles or use hazardous machinery while on therapy. Reduction of dosage may alleviate symptoms. Therapy need not be discontinued, but such patients should be observed with particular care.

Nephrotoxicity can occur and is probably a dose-dependent effect of colistimethate sodium. These manifestations of nephrotoxicity are reversible following discontinuation of the antibiotic.

Overdosage can result in renal insufficiency, muscle weakness, and apnea (see OVERDOSAGE section). See PRECAUTIONS, Drug Interactions subsection for use concomitantly with other antibiotics and curariform drugs.

Respiratory arrest has been reported following intramuscular administration of colistimethate sodium. Impaired renal function increases the possibility of apnea and neuromuscular blockade following administration of colistimethate sodium. Therefore, it is important to follow recommended dosing guidelines. See DOSAGE AND ADMINISTRATION section for use in renal impairment.

Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Colistimethate for Injection, USP and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.

C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.

If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile , and surgical evaluation should be instituted as clinically indicated.

PRECAUTIONS

General

Since Colistimethate for Injection, USP is eliminated mainly by renal excretion, it should be used with caution when the possibility of impaired renal function exists. The decline in renal function with advanced age should be considered.

When actual renal impairment is present, Colistimethate for Injection, USP may be used, but the greatest caution should be exercised and the dosage should be reduced in proportion to the extent of the impairment.

Administration of amounts of Colistimethate for Injection, USP in excess of renal excretory capacity will lead to high serum levels and can result in further impairment of renal function, initiating a cycle which, if not recognized, can lead to acute renal insufficiency, renal shutdown, and further concentration of the antibiotic to toxic levels in the body. At this point, interference of nerve transmission at neuromuscular junctions may occur and result in muscle weakness and apnea (see OVERDOSAGE section).

Signs indicating the development of impaired renal function include: diminishing urine output, rising BUN and serum creatinine and decreased creatinine clearance. Therapy with Colistimethate for Injection, USP should be discontinued immediately if signs of impaired renal function occur. However, if it is necessary to reinstate the drug, dosing should be adjusted accordingly after drug plasma levels have fallen (see DOSAGE AND ADMINISTRATION section).

Prescribing Colistimethate for Injection, USP in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

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