Vancomycin: pharmacology, indications, and dosage for serious bacterial infections

Drug Monograph

FOR SERIOUS INFECTIONS ONLY

Drug Monograph: Vancomycin

Drug Name -- Vancocin (brand), Vancomycin HCL -- oral (generic)

This is a time-dependent bactericidal antibiotic, which inhibits cell wall synthesis (Levinson, 2009).

Glycopeptides

VA Class - AM900

CAS Number 1404-93-9

Therapeutic Category -- a tricyclic glycopeptide antibiotic

Pharmacology

Vancomycin is not too well-absorbed from the GI tract after oral administration (Levinson 2009). When given parenterally, it penetrates the bile, pleural, pericardial, synovial and ascitic fluids. It is excreted unchanged by glomerular filtration (Levison).

When taken orally, Vancomycin is not absorbed in the intestines so that it can stop the growth of a severe intestinal condition known as Clostridium difficile-associated diarrhea (Medicine Net, 2012). When vancomycin is given by mouth, it is not absorbed by the body but remains in the intestines. This is to allow it to stop the growth of the Clostridium difficile bacteria. Vancomycin is intended as treatment only for bacterial infections of the intestines. It is not effective for other bacterial infections or infections caused by viruses. Its overuse can decrease its effectiveness (Medicine Net).

Indications

Vancomycin is intended for the treatment of serious or severe bacterial infections caused by susceptible strains of methicillin-resistant staphylococci (PDR, 2012, Drug.com, 2012). It is indicated for use by patients who are allergic to penicillin and cannot or fail to respond to other drugs. It is for infections caused by Vancomycin-susceptible organisms resistant to other anti-microbials. It is indicated as initial therapy when methicillin-resistant staphylococci infection is suspected. It is also effective in the treatment of staphylococcal endocarditis. It has been successfully used in combination with either rifampin or an aminoglycoside or both for early-onset prosthetic valve endocarditis, caused by S. epidermidis or diphtheroid. Its parenteral form may be administered orally in treating antibiotic-associated pseudomembranous colitis caused by C. difficile and for staphylococcal enterocolitis (PDR, Drug.com).

Vancomycin is the drug of choice against serious infection and endocarditis caused by Methicillin-resistant S. aureaus, Methicillin-resistant coagulase-negative Staphylococci, Streptococcus pneumoniae, B-Hemolytic streptococci, Corynebacterium group JK, Viridans streptococci and enterococci (Levinson, 2009). It has been used as an alternative drug for pneumococcal meningitis caused by strains with reduced penicillin sensitivity. But its erratic penetration into the CSF and reported clinical failures make it not advisable for use alone to treat pneumococcal meningitis.

Dosages

For Pediatric Patients

The usual does for all pediatric patients is 10 mg/kg by IV every six hours (PDR, 2012). The initial for newborns is 15 mg/kg, followed by 10 mg/kg every 12 hours for the first week of life. This is continued every 8 hours until their first month of age. Vancomycin should be given for at least 60 minutes. The initial dosage for pediatrics with renal impairment is not less than 15 mg/kg per day or 15 times the GFR in mL/min. Premature infants should have longer dosing intervals. PO administration should be 40 mg/kg/day in 3-4 divided doses for 7-10 days. The maximum is 2,000 mg/day, which may be diluted in 1 oz of water or administered through an NG tube (PDR).

Contraindications

Vancomycin is contraindicated to patients with hypersensitivity to vancomycin (Drug.com, 2012). Commercially prepared frozen Vancomycyn Hydrochloride injections in 5% dextrose may also be contraindicated to those with known allergic reaction to corn or corn products (Drug.com).

Drug-Drug Interactions

The patient should inform the doctor or pharmacist of all prescription and non-prescription or herbal products currently used (Medicine Net, 2012; Levinson, 2012). Aminoglycosides, amphotericin B, other antibiotics, and live bacterial vaccines are special mentions. If treatment requires anesthesia, the doctor or dentist should be told if the patient has been using Vancomycin. Although most antibiotics do not significantly affect hormonal birth control medications, they may decrease the effectiveness of these hormone medications and cause pregnancy (Medicine Net).

Current or sequential systemic or topical use of neurotoxic or nephrotoxic drugs should be carefully monitored (PDR, 2012). Periodic leukocyte count monitoring with drugs, which may cause neutropenia, should be performed. Serial monitoring of renal function and particular care after dosing should also be done to minimize the risk of nephrotoxicity with concomitant aminoglycoside (PDR).

Other Precautions and Potential Adverse Effects

A patient's medical history should be revealed before Vancomycin is administed

(Medicine Net, 2012). Elderly patients should be able to eliminate the drug from their bodies when needed. Otherwise, it should be administered to them with caution for possible sensitivity to its effects. It should be used on pregnant women only when clearly needed. Risks and benefits should be discussed with the doctor. Vancomycin does not pass on to breast milk and is thus not harmful to nursing infants. But the doctor must still be consulted on its effect on breastfeeding (Medicine Net).

Vancomycin may cause hypotension and cardiac arrest, though rarely, by rapid bolus administration (PDR, 2012). Ototoxicity has been reported and calls for caution for those with underlying hearing loss. Prolonged use can lead to an overgrowth of non-susceptible organisms. Safety and efficacy of administration through the intraperitoneal and intrathecal routes have not been confirmed. Use via the intraperitoneal route during dialysis has been reported to lead to a syndrome of chemical peritonitis (PDR).

Look-alike/Sound-alike Drugs and Prescription Refill Requirements

Vancomycin is 6th in the list of top 10 medications involved in drug errors (Medscape Pharmacists, 2007). These medications are the most commonly mis-used or mishandled some way by healthcare professionals, based on the database of the U.S. Pharmacopoeia. Liquid dose concentrations increase the risk of medication errors. There has been confusion over mL and tsp errors, which leads to overdose or under-dose of up to 5 times if undetected. Reconstituting antibiotics can also be risky as when the antibiotic powder is mixed with alcohol instead of distilled water (Medscape Pharmacists).

Vancomycin was also one of the 10 most frequently reported drugs with the highest adverse drug reactions by the Adverse Drug Reaction Reporting Program for 2003-2004 (Bebout, 2004). Half of all the 360 drugs were anti-infective (Bebout). #