Topical Antibiotics

     This chapter will look at topical antibiotics that are used to manage common infections.  This chapter will address three classes of antibiotics: skin applied antibiotics, antibiotics in the ear and antibiotics in the eye.

Skin applied antibiotics

     There are three major over the counter antibiotics for the skin: Neosporin, Bacitracin and Polysporin.  These medications are fairly similar.  Over the counter topical antibiotics decrease the risk of skin infection in a minor wound, but are not used to treat established skin infections. 

     Neosporin is a triple antibiotic that contains, neomycin, bacitracin and polymyxin.  This topical medications comes in an ointment and cream form.  It is the broadest of the topical antibiotics as it contains three antibiotics.  Many health care providers do not like to use this medication, as the neomycin is associated with a lot of allergic potential.  It often makes the skin red and painful and it may be more harmful than helpful in many people. 

     On the positive side, the addition of neomycin provides coverage against bacteria that are not covered by the other medications.

     Bacitracin contains only one antibiotic – bacitracin.  Bacitracin covers the most common causes of skin infections – staphylococcal and streptococcal infections.  Its coverage is not as broad as Neosporin, but is associated with less allergic potential. 

     Polysporin contains two antibiotics – bacitracin and polymyxin. 

     Bactine is an over the counter product that contains benzalkonium (antiseptic) and lidocaine (pain reliever).  It is used for the prevention of bacterial infection and a reduction in discomfort associated with cuts and scrapes. 

     Antiseptic agents are different than antibacterial agents.  Antiseptic agents reduce the growth or microorganisms.  They do not target a specific agent and can work on a variety of different agents including viruses, bacteria and protozoa. There is also less chance for drug resistant bacteria to develop to antiseptics. 

    On the down side there is some concern that antiseptics can damage healthy cells and inhibiting wound healing.  Although, most antiseptics have not demonstrated this negative effect in humans.   

     Hydrogen peroxide can also be used, but is not recommended for the use of minor wounds.  It is an antiseptic agent that can kill bacteria but has the potential to harm healthy tissue.  Of all antiseptics, hydrogen peroxide demonstrates the least effectiveness in the management of reducing bacterial counts. 

     Limited studies compare antiseptic agents to antibacterial agents in the management of minor cuts and wounds.  Most doctors currently recommend the use bacitracin or bacitracin/polysporin in the management of minor wounds.  This does not mean that Neosporin (unless you are sensitive to it) or the use of antiseptics are inappropriate.  More research is needed before a definitive answer can be given. 

     Mupirocin (Bactroban, Centany) is a topical prescription antibiotics.  Its claim to fame is in treating impetigo as well as MSRA.  It can also be used to treat wounds that become infected.  This drug treats the bacteria Streptococcus pyogenes and Staphylococcus aureus. 

     Individuals who are colonized with MRSA often use a nasal preparation of this antibiotic to eliminate it from their system.  This is especially important before going in for elective surgery. 

     Retapamulin (Altabax) is a newer topical ointment used in the treatment of impetigo.  Its major side effect is application site irritation. 

Eye antibiotics

     Many options are available in the management of bacterial infections in the eye.  Many doctors treat with quinolones (which have the lowest level of resistance) particularly moxifloxacin ([i]) (see Table 5).  Moxifloxacin has a low level of resistance and good coverage against organisms responsible for conjunctivitis.  Moxifloxacin also has a rapid onset of action and remains in the conjunctiva cell much longer than other antibiotics.  Moxifloxacin has shown to be provide a quicker cure – by 48 hours – when compared to polymyxin/trimethoprim ([ii]).

     Quinolones (applied in the eye) can be used in children as young as one.  Little gets into the blood stream and systemic effects are minimal and not a concern.  There is less concern for resistance to develop with the use of later generation topical antibiotic than with oral antibiotics (10). 

     Azithromycin is a newer medication used to treat bacterial conjunctivitis.  It has an improved dosing schedule, which may help improve compliance.  It has been shown to be similarly efficacious to tobramycin ([iii]).

     Older antibiotics such as sulfacetamide based products and Gentamicin have a tendency to burn and sting.  Other antibiotics, such as gatifloxacin (Zymar), are dosed very frequently (drops every two hours for 48 hours and then four times a day) and compliance becomes an issue. 

     Most antibiotics for bacterial eye infections are used for 5-7 days.  See table five for a listing of antibiotics used in the treatment of bacterial eye infections. 

Table 5: Antibiotics for Bacterial Eye Infections

Topical ear antibiotics

     Topical ear antibiotics are used for infections of the ear canal.  The most common infection that uses topical ear antibiotics is swimmers ear. 

       For mild cases 2% acetic acid is a possible first-line choice.  It may cause the ear canal to burn and irritate the skin and is therefore rarely used.      The addition of a steroid to acetic acid is accomplished in the product acetic aid/propylene glycol/hydrocortisone (VoSol HC). 

     Hydrocortisone/polymyxin/neomycin is more commonly used in the treatment of swimmers ear.    Hydrocortisone/polymyxin/neomycin should not be used if there is a tear in the ear drum as it can damage hearing.  Neomycin is irritating to the skin in a number of people who use this preparation. 

     More expensive options include quinolone antibiotics with or without steroids.  Ofloxacin is dosed 10 drops two times a day for adults and 5 drops two times a day for kids for 7 days.  Ciprofloxacin/hydrocortisone (Cipro HC otic) is dosed 3 drops twice a day for those over the age of one.  Ciprofloxacin/dexamethasone (Ciprodex Otic) is dosed 4 drops twice a day for those over the age of 6 months.    

     Ciprofloxacin/dexamethasone is indicated for patients with ear tubes and may be used if there is a tear in the ear drum. 

      Improvement should be noted in 2-3 days.  Resolution should occur in 7-10 days.  If there is no improvement noted a follow up appointment should be encouraged for a re-evaluation.  Sometimes preservatives in topical medications can incite local irritation leading to an unresolved infection.  Other times fungal infection is present – which do not respond to antibacterial medications.   

     When the ear is swollen it may not be possible to deliver drops into the lower part of the ear.  In this case the use of an ear wick will allow delivery of medication into the ear canal.  The health care provider will place a small piece of cotton into the ear that will allow ear drops to penetrate into the lower ear canal. 

     Before putting the drops in the ear they should be warmed.  The patient should lie on his or her side with the affected ear up.  The drops should ideally be placed by another person and the flap of skin covering the ear canal – called the tragus – should be pushed a couple of times after the drops are inserted.  The person should lie on the side for 5-10 minutes to assure adequate penetration of the medication.