Drugs for the ear
Anatomy of the ear
The ear has three major divisions: the external ear, middle ear, and inner ear (Fig. 106–1). Their primary features are as follows:
• The external ear consists of (1) the auricle or pinna (the cartilaginous flap visible on the side of the head that serves to collect sound waves); and (2) the external auditory canal (EAC), a skin-lined tube that directs sound waves from the auricle to the tympanic membrane (eardrum). The surface of the EAC is coated with cerumen (earwax), a hydrophobic substance that blocks penetration of water and helps protect against bacterial and fungal infection.
• The middle ear is the chamber that houses the malleus, incus, and stapes—three tiny bones that transmit sound vibrations from the eardrum to the inner ear. The middle ear is bounded laterally by the tympanic membrane, which walls off the middle ear from the external ear. The eustachian tube (auditory tube) connects the middle ear with the nasopharynx, and thereby allows air pressure within the middle ear to equalize with air pressure in the environment. The mucociliary epithelium that lines the eustachian tube sweeps bacteria out of the middle ear into the nasopharynx.
• The inner ear consists of the semicircular canals and the cochlea. The canals provide our sense of balance. The cochlea houses the apparatus of hearing.
Otitis media and its management
Otitis media (OM), defined as an inflammation of the middle ear, is the most prevalent disorder of childhood. The condition affects more than 75% of children by the age of 3 years, and about 95% by the age of 12. In the United States, OM is responsible for more than 30 million clinic visits a year.
Otitis media may result from bacterial infection, viral infection, or noninfectious causes. Only bacterial OM responds to antibiotics. Furthermore, most cases resolve spontaneously, making antibiotics largely unnecessary—even when bacteria are the cause. Nonetheless, antibiotics have been used routinely. In fact, OM is the most common reason for giving these drugs to kids—at an estimated cost of $3.5 billion a year.
Acute otitis media
Characteristics, pathogenesis, and microbiology
Acute otitis media (AOM) is defined by inflammation and fluid in the middle ear. Otalgia (ear pain) is characteristic, often causing the child to tug at the ear or just hold it. Other symptoms include fever, vomiting, irritability, impaired hearing, sleeplessness, and otorrhea (discharge from the ear, usually purulent [pus containing]).
AOM may be bacterial, viral, or both. In children with full-blown bacterial AOM, the inner ear is filled with purulent fluid, which can cause the tympanic membrane to bulge outward. If the membrane is perforated, otorrhea results. In children with nonbacterial AOM or with mild bacterial AOM, the tympanic membrane does not bulge. Of the two presentations—bulging or nonbulging eardrum—nonbulging is the more common.
How does AOM develop? As a rule, the process begins with a viral infection of the nasopharynx, which can cause blockage of the eustachian tube, which in turn can cause negative pressure in the middle ear. When the eustachian tube opens, causing pressure equalization, bacteria and viruses can be sucked in. If the mucociliary system is sufficiently impaired, it will be unable to transport these pathogens back to the nasopharynx. Otitis media results when bacteria colonize the fluid of the middle ear and/or when viruses colonize cells of the middle-ear mucosa. As indicated in Table 106–1, bacteria are present in 70% to 90% of fluid samples taken from the middle ear of children with AOM, and viruses are present in nearly 50%. The most common bacterial pathogens are Streptococcus pneumoniae (40% to 50%), Haemophilus influenzae (20% to 25%), and Moraxella catarrhalis (10% to 15%).
TABLE 106–1
Primary Pathogens Found in Fluid from the Middle Ear of Children with Acute Otitis Media
Pathogen | Children with the Pathogen (%) |
Streptococcus pneumoniae | 40–50 |
Haemophilus influenzae | 20–25 |
Moraxella catarrhalis | 10–15 |
No bacteria found | 20–30 |
Respiratory viruses (with or without bacteria) | 48 |
Diagnosis
To diagnose AOM, three elements must be present: (1) acute onset of signs and symptoms, (2) middle-ear effusion (MEE), and (3) middle-ear inflammation. The patient history will reveal whether onset of signs and symptoms has been both recent and rapid. The presence of MEE is indicated by any of the following: bulging tympanic membrane (the best predictor of MEE), limited mobility of the tympanic membrane, and otorrhea (fluid in the EAC following perforation of the tympanic membrane). Middle-ear inflammation is indicated by either (1) distinct erythema of the tympanic membrane or (2) distinct otalgia (discomfort, clearly referable to the ear, that disrupts normal activity or sleep).
Frequently, the diagnosis of AOM is somewhat uncertain. Why? Because in many cases, MEE can’t be confirmed. When the presence of MEE is questionable, a diagnosis of AOM may be considered, but cannot be deemed certain.
It is important to distinguish between AOM and otitis media with effusion (OME). As discussed below, children with OME have fluid in the middle ear but no signs of local or systemic illness. Prolonged OME is common following resolution of AOM.
Standard treatment
All children with AOM should receive required pain medication (eg, acetaminophen, ibuprofen, codeine), and some should receive antibiotics. Prescribing antibiotics for all children should be discouraged. Why? Because the vast majority (over 80%) of AOM episodes resolve spontaneously within a week. Hence, if antibiotics are prescribed routinely, most recipients will be taking drugs they don’t really need. Not only does this generate unnecessary expense, worse yet, it puts children at needless risk of adverse drug effects, increases their risk of recurrent AOM, and accelerates the emergence of antibiotic-resistant bacteria.
In 2004, two organizations—the American Academy of Pediatrics and the American Academy of Family Physicians—released guidelines for treating AOM in children. The guidelines stress the need for an accurate diagnosis, and they recommend basing treatment on three factors: age, illness severity, and the degree of diagnostic certainty.
For some patients, the guidelines include an important option—observation—rather than immediate treatment with antibacterial drugs. Observation is defined as management by symptomatic relief alone for 48 to 72 hours, thereby allowing time for AOM to resolve on its own. If symptoms persist or worsen, antibacterial therapy is then started. As part of this strategy, parents are informed about (1) the high probability of spontaneous AOM resolution, and (2) the drawbacks of giving antibiotics when they are not needed. Observation is considered appropriate only when follow-up can be ensured. The recommendation for observation is based on studies showing that:
• Most episodes of AOM resolve spontaneously.
• Immediate antibacterial therapy is only marginally superior to observation at causing AOM resolution, and is no better at relieving pain or distress.
• Parents find the observation approach acceptable.
• Delaying antibacterial therapy does not significantly increase the risk of mastoiditis, which can occur when bacteria invade the mastoid bone.
Criteria for choosing between observation and initial antibacterial therapy are summarized in Table 106–2. The choice is based on patient age, how certain the diagnosis is, and severity of symptoms. As indicated, all children less than 6 months old should receive antibiotics, regardless of diagnostic certainty or symptom severity. Among children 6 months to 2 years old, antibiotics are indicated whenever the diagnosis is certain. If the diagnosis is uncertain, antibiotics are indicated only if symptoms are severe. For children age 2 years and older, antibacterial therapy is indicated only if the diagnosis is certain, and then only if symptoms are severe. In all other cases, observation is the preferred strategy.
TABLE 106–2
Criteria for Choosing Initial Antibacterial Therapy Versus Observation in Children with AOM
Management Recommendation | ||
Age | Certain Diagnosis | Uncertain Diagnosis |
Less than 6 months | Antibacterial therapy | Antibacterial therapy |
6 months to 2 years | Antibacterial therapy | Antibacterial therapy if illness is severe; observation if illness is not severe* |
2 years and older | Antibacterial therapy if illness is severe; observation if illness is not severe* | Observation, regardless of symptom severity |
*Severe illness = moderate to severe otalgia or fever of 39°C or higher, nonsevere illness = mild otalgia and fever below 39°C in the past 24 hours.