Hearing Loss

Hearing loss is the complete or partial inability to hear and is one of the most common sensory impairments worldwide, clinically defined as a decibel loss exceeding 25 dB at frequencies between 250 and 8000 Hz.^[1] It is classified into three types based on where the pathology lies: conductive hearing loss (CHL), from physical anomalies of the outer or middle ear that impede sound transmission (cerumen impaction, otitis media or externa, tympanic membrane perforation, otosclerosis); sensorineural hearing loss (SNHL), from defective inner ear (cochlear) components or neural signaling to the auditory cortex — often permanent, and including age-related presbycusis, noise-induced hearing loss, and drug-induced ototoxicity; and mixed hearing loss, combining both.^[1]

This is a genuinely common problem. Globally, over 5% of the population — some 430 million people — require rehabilitation for disabling hearing loss (greater than 35 dB in the better ear), a figure projected to exceed 700 million by 2050; more than a quarter of adults over 60 are affected.^[2] In Canada specifically, approximately 20% of adults aged 20 to 79 have audiometrically measured hearing loss, a prevalence that climbs to roughly 65% among adults aged 70 to 79.^[1] Left unaddressed, hearing loss carries real downstream costs — increased fall risk, social isolation, and an association with accelerated cognitive decline and dementia in older adults, reduced social and emotional functioning in working-age adults, and delayed speech, language, and academic development in children.^[1]

While most hearing loss is gradual and non-urgent, this chapter gives particular weight to two situations where a pharmacist's specific knowledge changes outcomes. The first is ototoxic drug-induced hearing loss: over 600 categories of drugs carry documented ototoxicity potential,^[3] and a 2020 comprehensive review identified 194 systemically administered medications with evidence of cochleotoxicity, vestibulotoxicity, or dizziness — most commonly antimicrobials, psychotropics, antihypertensives/antiarrhythmics, NSAIDs, and antineoplastics.^[4] Recognizing which agents carry the highest risk, which effects are typically reversible versus permanent, and when monitoring or dose modification is warranted is squarely within a pharmacist's scope and genuinely changes outcomes. The second is sudden sensorineural hearing loss (SSNHL), a rare but real otologic emergency — see Recognize the Condition and Red Flags for Referral — where recognizing the time-limited window for effective treatment, rather than treating it as routine hearing loss, can be the difference between recovery and permanent deafness.

Conductive hearing loss

Results from physical anomalies that impede sound wave transmission through the outer or middle ear. In the ear canal, otitis externa presents with inflammation and edema, while cerumen impaction, foreign bodies, and neoplasms cause canal obstruction. Tympanic membrane perforations follow repeated infection or trauma, with roughly 80% resolving spontaneously within 3 months. Otitis media presents with pain and a red, bulging membrane; unilateral pulsatile tinnitus with a bulging red mass directly behind the membrane suggests a glomus tumour, while epithelial debris behind the membrane suggests a cholesteatoma. Conductive hearing loss with a normal otoscopic exam points to middle ear pathology such as otosclerosis, which typically presents with a positive family history.^[1]

Sensorineural hearing loss

Results from defective inner ear (cochlear) components or neural signaling to the auditory cortex, and is frequently permanent. The most common cause is age-related hearing loss (presbycusis), which is slowly progressive, bilateral, and symmetrical, and is aggravated by noise damage, ototoxic agents, and other otologic disorders — it initially impairs high-frequency sensitivity before also compromising sound clarity.^[1] Noise-induced hearing loss is a similarly gradual, bilateral decline from chronic occupational or recreational noise exposure, and is genuinely preventable.^[1] Ototoxic medications typically also cause a gradual, bilateral SNHL — see Risk Factors and Pharmacologic Treatment Options and Drug Tables for the full picture, including the agents and situations where the pattern differs (asymmetric, or acute rather than gradual).^[1] A gradual, unilateral SNHL, in contrast, raises the possibility of an acoustic neuroma (vestibular schwannoma), which can present with focal neurologic signs; unilateral SNHL accompanied by vertigo raises the possibility of Ménière disease.^[1] In pediatric patients, SNHL warrants a family history of genetic hearing conditions and testing for TORCH infections (toxoplasmosis, rubella, cytomegalovirus, herpes simplex, and others including syphilis).^[1]

Mixed hearing loss

Combines both CHL and SNHL — chronic middle ear disease such as severe otosclerosis, cholesteatoma, or neoplasm can produce this pattern directly, or a primary CHL and an unrelated secondary SNHL (or vice versa) can simply coexist in the same patient.^[1]

Sudden sensorineural hearing loss (SSNHL) — a distinct, time-critical presentation

General risk factors for hearing loss

• Age — the single strongest predictor of presbycusis, and prevalence climbs steeply after age 60-70.^[1][2]
• Noise exposure, occupational or recreational — a preventable cause of gradual bilateral SNHL.^[1]
• Cardiovascular disease and smoking — recognized modifiable risk factors that aggravate presbycusis.^[1]
• Family history / genetic predisposition — relevant both to non-syndromic hereditary hearing loss and, specifically, to genetic susceptibility to aminoglycoside ototoxicity (see below and Special Populations).
• Exposure to ototoxic medications — the focus of the remainder of this section.

Ototoxic-drug risk factors — the pharmacist-critical core of this chapter

Ototoxicity severity and incidence is generally dose-dependent and cumulative, and is influenced by age, comorbid renal or cardiac disease, genetic susceptibility, drug type, route, duration of therapy, and pre-existing hearing loss.^[3] Reported incidence varies by agent: roughly 63% with aminoglycosides, 23-50% in adults (up to 60%, and in some series up to 100%, in children) with cisplatin, and 6-7% with furosemide.^[3]

History

A detailed history refines the differential meaningfully. Establish onset and course (sudden versus gradual — this alone drives urgency), whether the loss is unilateral or bilateral, and associated symptoms: vertigo, tinnitus, focal neurologic symptoms, and ear pain. Ask specifically about environmental and occupational noise exposure — and, critically for this chapter, take a complete medication history including any current or recent ototoxic agent (aminoglycosides, loop diuretics, platinum chemotherapy, high-dose salicylates, high-dose macrolides — see Pharmacologic Treatment Options and Drug Tables). This medication-focused history is genuinely one of the most valuable contributions a pharmacist can make to the diagnostic picture.^[1]

Physical examination

Visual inspection of the outer ear plus otoscopic examination of the ear canal, tympanic membrane, and middle ear space can reveal infection, trauma, neoplasm, or congenital abnormality, and is what actually rules a conductive cause in or out. The Rinne and Weber tuning fork tests (typically a 512 Hz fork) help distinguish conductive from sensorineural hearing loss, though test implementation and accuracy vary considerably and results should be interpreted alongside the rest of the clinical picture rather than in isolation.^[1]

Note that the Weber test only lateralizes with asymmetric hearing loss — in symmetric hearing loss of either type, it will be perceived equally at the midline.^[1] A focused neurologic exam, including cranial nerves III through XII, is warranted whenever a central cause is plausible.^[1]

Investigations: audiometry is the definitive test

Audiometry is indicated in any patient with a subjective hearing complaint and remains the definitive diagnostic test. A full audiologic assessment includes history, otoscopy, acoustic immittance measures (tympanometry — assessing middle ear function and mobility of the tympanic membrane), pure-tone threshold testing across the conventional range (250-8000 Hz), speech testing, and counseling.^[1] In Canada, family physicians can identify a local audiologist through the Canadian Academy of Audiology's public directory (findanaudiologist.ca), and a preliminary referral to audiology is reasonable for any patient with a subjective hearing complaint.^[1] For patients on, or about to start, a known ototoxic agent, audiometry additionally serves a monitoring role — see Monitoring & Follow-Up for the specific baseline-and-serial protocol.

Imaging and laboratory testing

Most hearing loss is diagnosed clinically without further testing. A bacterial culture is reasonable for acute otitis externa unresponsive to first-line therapy. For unilateral, asymmetric, or otherwise atypical SNHL — including suspected acoustic neuroma — gadolinium-enhanced MRI is the investigation of choice and is typically ordered by OtoHNS; CT is used for suspected temporal bone fracture after trauma.^[1]

Differential diagnosis

• Accurately classify hearing loss as conductive, sensorineural, or mixed, and identify a treatable underlying cause wherever one exists.
• Recognize sudden sensorineural hearing loss immediately as a time-critical emergency and triage it within its effective treatment window, rather than as routine hearing loss.
• For ototoxic drug-induced hearing loss specifically: identify the causative agent and, where clinically feasible, coordinate with the prescriber on dose adjustment, interval change, agent substitution, or discontinuation — balanced explicitly against the necessity of the causative therapy (a serious infection requiring an aminoglycoside, or cancer requiring cisplatin, cannot simply be stopped without a considered risk-benefit decision).
• Proactively identify high-risk patients (planned aminoglycoside or platinum-chemotherapy course, concurrent aminoglycoside-plus-loop-diuretic, high-dose salicylate or macrolide therapy) and support baseline and serial monitoring rather than waiting for symptoms to surface unprompted.
• Minimize avoidable combined ototoxic exposure — most importantly, flag and avoid the aminoglycoside-plus-loop-diuretic combination whenever a reasonable alternative exists.
• Support communication and quality of life through amplification (hearing aids, cochlear implants) and rehabilitation once a cause is identified or found to be irreversible.
• Educate patients on early symptom reporting — tinnitus and subjective hearing change are practical, low-cost warning signs that keep an ototoxic effect within a still-modifiable window.

Ototoxic drug-induced hearing loss — the pharmacist's core decision

Before starting a planned course of a known ototoxic agent, where clinically feasible flag baseline audiometry (and, at minimum, a baseline tinnitus/hearing/dizziness check) to the prescriber and care team before the first dose — see Monitoring & Follow-Up for the specific timing.^[8][3] During therapy screen systematically for tinnitus, subjective hearing change, aural fullness, or dizziness at every contact, and support serial audiometry per protocol (for example, before each cisplatin cycle).^[8][3] Aminoglycoside plus loop diuretic together flag this combination to the prescriber explicitly — it is the single highest-risk pairing in this chapter (see Risk Factors) — and confirm the loop diuretic, if genuinely needed at a high dose, is given by slow infusion rather than rapid bolus.^[6] A significant threshold shift, new tinnitus, or new dizziness is reported or detected escalate to the prescriber promptly. The decision is not automatically "stop the drug" — it is a genuine risk-benefit discussion: dose reduction, a longer dosing interval, an agent switch, or discontinuation are all reasonable options, weighed explicitly against the necessity of the causative therapy (a life-threatening infection requiring an aminoglycoside, or a cancer requiring cisplatin, may reasonably continue with closer monitoring rather than being stopped outright).^[3]

Conductive and other non-drug-related hearing loss

Treat conductive causes on their own merits — cerumen impaction with irrigation or cerumenolytics (see the Cerumen Impaction chapter), acute otitis externa with antibiotic otic drops, acute otitis media with oral antibiotics, and tympanic membrane perforation, otosclerosis, or cholesteatoma with surgical referral as appropriate.^[1] Presbycusis and noise-induced hearing loss are managed with amplification and prevention rather than pharmacotherapy — see Non-Pharmacologic Treatment.

Amplification and rehabilitation

• Hearing aids — the mainstay for SNHL, particularly presbycusis. Current evidence demonstrates genuine quality-of-life improvements related to general health and hearing in adults with mild to moderate hearing loss.^[1]
• Cochlear implants — for profound SNHL insufficiently restored by hearing aids. This is beyond a pharmacist's scope of practice, but relevant to comprehensive patient counseling: adult candidacy generally requires the patient to have been postlingually deafened, to have no medical contraindications, and to hold realistic expectations about the degree of hearing improvement after implantation.^[1]
• Assistive listening devices (frequency modulation/loop systems, alerting devices, telecommunication devices, captioning) and, where appropriate, sign language or other communication training, are part of a comprehensive rehabilitation plan alongside amplification.^[2]
• Surgical options exist for specific conductive causes — tympanoplasty for perforation, stapedectomy for otosclerosis, tympanoplasty with mastoidectomy for cholesteatoma — but hearing loss caused by a cerebellopontine angle tumour itself is not restored by tumour resection surgery.^[1] These are OtoHNS decisions, not pharmacist ones, but worth knowing when counseling a patient about what to expect from a referral.

Prevention

• Noise protection — hearing-protector devices and responsible personal listening device use are effective prevention strategies for noise-induced hearing loss; occupational hearing-conservation programs (increased earplug use where appropriate) reduce workplace noise-induced hearing loss.^[1]
• Addressing modifiable presbycusis risk factors — smoking cessation and cardiovascular risk-factor management, alongside noise avoidance.^[1]
• Avoiding avoidable combined ototoxic exposure — most importantly, avoiding the aminoglycoside-plus-loop-diuretic combination when a reasonable alternative exists (see Risk Factors and Choose Initial Treatment).
• Noise avoidance during and after ototoxic drug therapy — patients on a course of a known ototoxic agent should be counseled to avoid loud noise exposure during treatment and for several months afterward, since aminoglycosides can remain within inner ear hair cells for months after the course ends, and noise exposure has been shown to exacerbate both aminoglycoside- and cisplatin-induced ototoxicity.^[8]

Patient education

• Report tinnitus and subjective hearing change immediately during any course of a known ototoxic agent, rather than waiting for it to worsen or resolve on its own — this is the single most practical thing a patient can do to keep an ototoxic effect within its modifiable window.^[8]
• Explain to patients starting a planned ototoxic course (an aminoglycoside, cisplatin, or high-dose therapy with a loop diuretic, salicylate, or macrolide) why monitoring is being offered — it is not routine paperwork, it is what allows dose or agent modification while the effect may still be reversible.
• For patients with sudden hearing loss: explain plainly why this is not "just wait and see," and that a real, time-limited treatment window exists for corticosteroid therapy.^[1]
• Speaking clearly, facing the patient, and minimizing background noise measurably improves the pharmacy encounter for a patient with any degree of hearing loss — patients with hearing loss consistently report weaker relationships with their health care providers and poorer overall care experiences when this is not done.^[1]
• Counsel that hearing loss affects the whole family, not only the patient — communication difficulties and lifestyle changes have real effects on caregivers and household members, and this is worth acknowledging directly.^[1]

Pediatrics

Aminoglycosides (most often gentamicin) are commonly used in neonatal intensive care, typically for prophylaxis in preterm infants and discontinued once sepsis is ruled out under 72 hours — but continued for 10-15 days if sepsis is confirmed.^[6] Cisplatin ototoxicity is materially more common and more severe in children than adults, with the highest risk in children under 5.^[3] Congenital or early-childhood SNHL warrants a family history and TORCH workup.^[1] The Canadian Infant Hearing Task Force recommends universal newborn hearing screening before 1 month of age, with confirmatory diagnostic testing by a pediatric audiologist by 3 months and intervention started by 6 months for babies with confirmed hearing loss — though not every province currently has a high-quality early hearing detection and intervention program, so a family physician or pharmacist should not assume this has automatically happened.^[1] Cystic fibrosis patients receive repeated aminoglycoside courses for Pseudomonas infection, and audiological surveillance gaps are real and documented — one survey found only about a quarter of accredited CF care centers performed routine audiometric evaluation at all.^[3] Some children develop progressive hearing loss later in childhood that newborn screening will not have caught — investigate any parent-reported hearing concern with a full history, exam, and pediatric audiology referral rather than reassurance alone.^[1]

Pregnancy and breastfeeding

Aminoglycosides cross the placenta and carry a recognized risk of fetal ototoxicity; use only when a serious maternal infection genuinely requires them and no comparably effective, less ototoxic alternative exists, and coordinate with obstetrics. High-dose salicylates and cisplatin both carry their own separate pregnancy-specific risks beyond ototoxicity and should be managed by the treating specialist with these considerations in mind.

Renal impairment

Aminoglycoside clearance depends heavily on renal function, and reduced clearance prolongs high serum levels — directly raising ototoxicity (and nephrotoxicity) risk; therapeutic drug monitoring and renal-function-adjusted dosing are essential, not optional, in this group.^[6] This is not a coincidence: the inner ear hair cells and renal proximal tubule cells share a specific vulnerability to aminoglycoside uptake and retention, which is why the two toxicities travel together clinically.^[6] Furosemide dosing and infusion rate also need particular attention in renal impairment, given the higher doses often required.

Older adults

Presbycusis raises baseline hearing loss and reduces the detectable margin before a new ototoxic effect becomes clinically apparent, making a genuine baseline audiogram more valuable, not less, before starting a planned ototoxic course in this group. Polypharmacy also raises the real possibility of cumulative or stacked ototoxic exposure over time (for example, chronic NSAID or high-dose ASA use layered onto an acute aminoglycoside course) — a targeted medication review is a genuinely useful pharmacist contribution here.

Genetic susceptibility — a real, underrecognized risk factor

Certain mitochondrial DNA mutations, most notably the m.1555A>G variant, are linked to markedly increased susceptibility to aminoglycoside-induced ototoxicity.^[3] Ask about a family history of early, unexplained, or specifically aminoglycoside-associated hearing loss before a planned aminoglycoside course wherever that history is available — it is a genuine, actionable clue, even though formal genetic testing is not typically part of routine pharmacy or primary-care workflow.

Oncology patients

For patients on cisplatin or other platinum-based chemotherapy, ototoxicity monitoring is a genuine multidisciplinary responsibility — oncologist, audiologist, and pharmacist all have a role in ensuring baseline and pre-cycle audiometry actually happens rather than being assumed to be someone else's job.^[3]

Baseline and serial audiometry for ototoxic drug therapy

Ideally, baseline audiometric testing is completed before any ototoxic drug is given, so later results have a clear point of comparison — this matters most for patients with a high underlying prevalence of pre-existing, undetected hearing loss (older adults especially), where the absence of a baseline makes it much harder to attribute a later change to the drug rather than to prior hearing status.^[8] Established timing benchmarks: baseline audiometric testing within 24 hours of starting a chemotherapeutic agent, and within 72 hours of starting an aminoglycoside antibiotic.^[3] A comprehensive baseline includes conventional pure-tone audiometry (250-8000 Hz), and — where available — high-frequency audiometry (9000-20,000 Hz), tympanometry, and otoacoustic emission testing.^[8][3] High-frequency testing matters because ototoxic hearing change characteristically begins above 8000 Hz, in the basal turn of the cochlea, before progressing to the lower, speech-relevant frequencies — so a change can be detected by high-frequency audiometry well before it would show up on a conventional audiogram alone.^[8][3] Serial monitoring during therapy should follow protocol for the specific agent — for example, audiometry before every cisplatin cycle, and periodic testing during a prolonged aminoglycoside course.^[3]

A practical bedside proxy: systematic tinnitus and subjective hearing-change screening

Formal serial audiometry is not always feasible for an acutely ill or hospitalized patient. Systematically asking about tinnitus, subjective hearing change, aural fullness, and dizziness at every clinical contact during ototoxic therapy is a genuinely practical, low-cost complement to formal audiometry, and is strongly encouraged even where it has not traditionally been part of routine tinnitus assessment.^[8] Structured tools such as the Tinnitus Handicap Inventory and Dizziness Handicap Inventory can help quantify the functional impact when a symptom is reported.^[3] There is no single universally agreed numeric threshold for a "significant" shift across every monitoring protocol — the practical rule for a pharmacist is to treat any new patient-reported hearing, tinnitus, or dizziness symptom during ototoxic therapy as worth escalating promptly, rather than waiting for it to meet a formal audiometric cutoff.

Coordination is the whole point

Effective ototoxicity monitoring is a genuinely multidisciplinary effort — oncologist or prescribing physician, otolaryngologist, audiologist, pharmacist, and nursing staff all have a role, and monitoring programs fail most often not from a lack of good tests but from unclear ownership of who orders the baseline test and who acts on a positive finding.^[3] A pharmacist's practical contribution is threefold: flagging the baseline-audiometry opportunity when a planned ototoxic course is first ordered, asking about tinnitus/hearing/dizziness at every subsequent contact, and escalating any positive finding to the prescriber promptly rather than assuming someone else will catch it.

Sudden sensorineural hearing loss follow-up

Recheck hearing status after completing the oral corticosteroid taper. If recovery is incomplete 2 to 6 weeks after symptom onset, or systemic steroids were contraindicated from the outset, urgent referral for intratympanic corticosteroid salvage therapy is the next step rather than repeating or extending the oral course.^[1][5]

Complications of unaddressed or undetected hearing loss

The consequences of missing an ototoxic effect, or of hearing loss going unaddressed more broadly, are genuine, not theoretical: permanent hearing loss extent generally depends on how early therapy was modified once a change was detected; tinnitus can persist independent of any measurable threshold change; vestibulotoxicity raises real fall risk, particularly in older adults; and unaddressed hearing loss more broadly carries a documented association with social isolation, depression, and accelerated cognitive decline in adults, and with delayed speech, language, and academic development in children.^[1][2] These downstream effects are exactly why early detection and prompt escalation, rather than a "wait and see if it's really a problem" approach, are the standard for a patient on ototoxic therapy.

1. SSNHL with incomplete recovery 2-6 weeks after starting oral corticosteroids, or steroids contraindicated from the outset: refer urgently for intratympanic corticosteroid salvage therapy rather than repeating or extending the oral course.
2. A documented significant audiometric threshold shift, new tinnitus, or new dizziness reported during a planned course of a known ototoxic agent: escalate to the prescriber immediately to discuss dose reduction, a longer dosing interval, an agent switch, or discontinuation — weighed explicitly against the necessity of the causative therapy, not defaulted to automatic discontinuation or automatic continuation.
3. Concurrent aminoglycoside and loop diuretic use where both are judged clinically necessary: do not simply proceed on standard monitoring for either drug alone — flag for closer, more frequent monitoring and confirm the diuretic is given by slow infusion rather than rapid bolus.
4. A persistent hearing complaint despite a normal audiogram, or no clear cause found on initial workup: refer to audiology or OtoHNS for advanced testing rather than dismissing the complaint.
5. Unilateral, gradually progressive SNHL not explained by the history: refer for gadolinium-enhanced MRI to exclude an acoustic neuroma rather than assuming routine presbycusis.
6. A pediatric cystic fibrosis or oncology patient who does not appear to be receiving the guideline-recommended baseline and serial audiometry: raise this gap proactively with the care team rather than assuming it is being handled elsewhere — documented practice gaps in this exact scenario are real, not hypothetical.
7. Hearing aids insufficiently restoring function in profound SNHL: refer for cochlear implant candidacy assessment rather than continuing to adjust amplification alone.

• Treating any sudden hearing loss as routine and worth "watching for a while" rather than immediately distinguishing conductive from sensorineural causes and triaging accordingly.
• Assuming loop diuretic ototoxicity is always benign and fully reversible, and missing the additive, potentially permanent risk when combined with a concurrent aminoglycoside.
• Starting a planned course of a known ototoxic agent without flagging baseline audiometry as an option, then having no point of comparison if a change is reported later.
• Not asking specifically about tinnitus in a patient on sustained high-dose salicylate therapy — missing the earliest, most reversible warning sign.
• Assuming macrolide-related ototoxicity only occurs with high-dose intravenous erythromycin, and missing the demonstrated cumulative-dose risk from everyday oral macrolide courses.
• Treating unilateral, gradually progressive SNHL as ordinary presbycusis without asking about laterality or considering imaging to exclude an acoustic neuroma.
• Unilaterally discontinuing or delaying a life-saving aminoglycoside or cisplatin course without coordinating the decision with the prescriber.
• Not asking about a family history of early or unexplained hearing loss before an aminoglycoside course, missing a genuine genetic-susceptibility clue.
• Assuming combined ototoxic exposures simply add together — a combination can convert an otherwise fully reversible effect (such as salicylate-induced hearing loss) into a permanent one.
• Forgetting to counsel on noise avoidance during and for several months after a course of ototoxic therapy.
• Speaking too quietly, too fast, or with excess background noise when counseling a patient who already has hearing loss — a preventable, avoidable barrier to the rest of the encounter.

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Sudden Sensorineural Hearing Loss — Corticosteroid Therapy

Actual pharmacologic treatment for confirmed or strongly suspected SSNHL. Time-sensitive: offer within 2 weeks of symptom onset and refer urgently to OtoHNS regardless of which agent is used.

Aminoglycosides

The most consistently high-risk ototoxic drug class. Cochleotoxicity and/or vestibulotoxicity occurs in up to ~20% of patients receiving multi-day IV therapy. Gentamicin and tobramycin are considered relatively more vestibulotoxic; amikacin, neomycin, and kanamycin relatively more cochleotoxic — though each affects both systems to some degree. Concurrent loop diuretic or glycopeptide use, renal impairment, prolonged/repeated courses, and genetic susceptibility (mitochondrial m.1555A>G) all raise risk; effects are frequently irreversible.

Loop Diuretics

Classically reversible cochleotoxicity via stria vascularis edema when used alone — but risk becomes additive, and can become permanent, when combined with a concurrent aminoglycoside. This is the single highest-risk ototoxic combination covered in this chapter.

Platinum-Based Chemotherapy

Dose-dependent and cumulative; often permanent. Markedly higher risk in young children, particularly under age 5.

Salicylates

Classically dose-related and reversible. Tinnitus is typically the earliest warning sign and usually resolves within days of dose reduction or discontinuation.

Macrolide Antibiotics

Risk is driven by cumulative dose and duration rather than a single short course. Reversible tinnitus is more common than measurable hearing loss; intermediate- and long-acting agents (azithromycin, clarithromycin) show the strongest association.

Other Notable Ototoxic Agents

Rounding out this chapter's pharmacist-critical list — both are classic, genuinely testable ototoxicity teaching points beyond the core drug classes above.