Mycitracin

Uses

Ointment may be used in the treatment of infected wounds,burns or skin grafts, and it is also of value in the preparation of donor sites for skin grafting and in the prevention of infection of extensive burns and contaminated wounds. It is of value in the local treatment of chronicvaricose or other indolent ulcers. The preparation is also of value in thetreatment of furuncles, carbuncles, pyoderma, sycosis barbae, impetigo and acne. It has also been used in dealing with secondary infected skin lesions of scabies, pediculosis, tinea pedis and contact and allergic dermatitis.

Mycitracin is also used to associated treatment for these conditions: Acute Otitis Media, Bacteremia caused by Enterobacter aerogenes, Bacterial Conjunctivitis, Bacterial Infections, Chronic Otitis Media, Escherichia urinary tract infection, Klebsiella bacteraemia, Meningitis caused by Haemophilus influenzae, Meningitis, Bacterial, Ocular Inflammation, Otitis Externa, Otorrhoea, Superficial ocular infections of the conjunctiva caused by susceptible bacteria, Superficial ocular infections of the cornea caused by susceptible bacteria, Urinary Tract Infection, Ocular bacterial infections

How Mycitracin works

The alpha and gamma diaminobutyric acid of a positively charged polymyxin B forms an electrostatic interaction with the phosphate groups of a negatively charged lipid A on the outer membrane of a Gram negative bacterium. Calcium and Magnesium ions are displaced from phosphates of the membrane lipids, destabalising the lipopolysaccharide (LPS), increasing membrane permeability, causing cytoplasmic leaking, and killing the cell.

Polymyxin B can also bind and neutralize LPS released during bacterial lysis, preventing reactions to endotoxin.

A third activity of polymyxin B is the inhibition of type II NADH-quinone oxidoreductases in the bacterial inner membrane, which are essential for respiration.

Polymyxin is active against common Gram negative bacteria but not Gram negative cocci, Gram positive bacteria, or anaerobic bacteria.

Dosage

Mycitracin dosage

Topical: Thisointment should be applied thinly over the affected area after cleaning it. One to three daily applications should be continued until the infection is controlled and healing complete.

Side Effects

Common side effects are Nausea; Vomiting; Pain, burning, or swelling; Skin rashes; Possible kidney problems; Hearing loss; Dizziness; Unusual numbness of the skin; Muscle twitching; Seizures; Pain; Redness; Swelling at the injection site.

Toxicity

Nephrotoxicity can occur in patients as polymyxin B is thought to accumulate in renal cells after renal tubular reabsorption. This accumulation can lead to apoptosis of renal cells and decrease in renal function. In recent studies, acute kidney injury (AKI) has been seen in 31.3% to 39.4% of patients receiving polymyxin B.

Overdose cases can cause neuromuscular block leading to apnea, muscular weakness, vertigo, transient facial parasthesia, slurred speed, vasomotor instability, visual disturbance, confusion, psychosis, and respiratory arrest. Renal failure has also been seen through decreased urine output, and increased serum concentrations of blood urea nitrogen.

Overdose of polymyxin B is treated by stopping the drug and beginning symptomatic treatment. Intravenous administration of mannitol may enhance renal clearance, and hemodialysis may manage renal complications.

Safety of polymyxin B has not been established in pregnancy, breast feeding, pediatrics, and geriatrics. Polymyxin B should no be used in pregnancy unless the benefit outweighs the risk. Nursing mothers should either stop nursing or stop polymyxin B treatment depending on the risks to both the mother and child. Pediatric patients should be frequently monitored for renal function and no dosing information is available in children under 2 years of age. Geriatric patients should have renal function assessed before and regularly during therapy.

Precaution

This ointment is not intended for sterile use in surgical procedures such as those involving abdominal or thoracic cavities as there is evidence that neomycin, when in contact with peritoneal or pleural tissues, can potentiate neuromuscular block in patients under the influence of muscle relaxants, producing respiratory paralysis. As with other antibiotic preparations prolonged use may result in overgrowth of non- susceptible organisms. Ototoxicity to neomycin has been reported.

In neonates and infants, absorption by immature skin may be enhanced and renal function may be immature.

Interaction

The concurrent or sequential use of other neurotoxic and/or nephrotox-ic drugs with Polymyxin B sulfate, particularly bacitracin, kanamycin, streptomycin, tobramycin, amikacin, cephaloridine, cephalothin, paromycin, polymyxin E (colistin), neomycin, gentamicin, and vancomycin, Bumetanide, celecoxib, cisplatin, cyclosporine, diclofenac, misoprostol, diphenhydramine, ibuprofen, naproxen, esomeprazole, etodolac, general anesthetic, gentamycin, ketorolac, meloxicam, tenofovir etc should be avoided.

Volume of Distribution

1 compartment models estimate the volume of distribution to be 34.3L to 47.2L. However, the general consensus is that the volume of distribution is yet to be determined.

Elimination Route

Administration by the oral route does not lead to absorption.

Half Life

In one study the half life was 9 to 11.5 hours. However, a Canadian monograph states the half life to be 6 hours, and 48-72 hours in patients with renal insufficiency.

Clearance

1 compartment models estimate clearance to be 2.37L/h to 2.5L/h.

Elimination Route

Polymyxin B is proposed to be primarily eliminated through renal tubular reabsorption and non-renal pathways. Urine collection in humans and animals show 1. However, a Canadian product monograph states the drug is primarily eliminated through the kidneys and that 60% of polymyxin B is recovered in the urine. This discrepancy can be explained by the 12 to 24 hour lag time between administration and significant elimination of polymyxin B. Non-renal elimination is not well understood but all 4 components of polymyxin B have been detected in bile.

Pregnancy & Breastfeeding use

Pregnancy category C. There is little information to demonstrate the possible effect of topically applied neomycin in pregnancy and lactation. However, neomycin present in maternal blood can cross the placenta and may give rise to a theoretical risk of fetal toxicity, thus this ointment is not recommended in pregnancy and lactation.

Contraindication

This ointment should not be used in individuals who have shown sensitivity to any of the components. A possibility of increased absorption exists in very young children, thus this ointment is not recommended for use in neonates. Hypersensitivity.

Special Warning

Children and Infants: This ointment is suitable for use in children at the same dose as adults, but the dose should be reduced in infants. This ointment is not recommended for use in neonates.

Acute Overdose

Polymyxin-induced toxicity associated with overdose has been reported. Overdose of Polymyxin can result in neuromuscular blockade, which can lead to apnea, muscular weakness, vertigo, transient facial paresthesia, slurred speech, vasomotor instability, visual disturbance, confusion, psychosis and possible respiratory arrest. Overdose can also cause renal failure characterized by decreased urine output and increased serum concentrations of BUN and creatinine. There is no specific antidote for Polymyxin B Sulfate overdose. In case of Polymyxin B Sulfate overdose, the drug should be stopped and symptomatic treatment instituted. Quick diuresis by IV administered mannitol may help to enhance renal clearance of the drug and thus to reduce serum drug levels. Hemodialysis or peritoneal dialysis may help in order to manage renal complications.

Storage Condition

Store below 30˚C. Keep all medicine out of reach of children.

Innovators Monograph

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