Comprehensive medication guide to Gentamicin including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
$0–$10 copay for ophthalmic/topical at Tier 1 on most commercial and Medicare Part D plans. Injectable administered inpatient is covered under Medicare Part A/B facility fees. No prior authorization required for standard formulations.
Estimated Cash Pricing
$38–$44 retail for ophthalmic (Gentak); as low as $9–$14 with GoodRx or SingleCare coupons. Topical cream runs ~$31 for two 15g tubes with coupons. Injectable formulations vary; typically $18–$26 with discounts.
Medfinder Findability Score
75/100
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Gentamicin is an aminoglycoside antibiotic derived from Micromonospora purpurea, a soil-dwelling actinomycete bacterium. It has been a cornerstone of infectious disease treatment since its introduction in the 1960s, and remains one of the most important antibiotics for treating serious gram-negative bacterial infections.
Gentamicin is available in several formulations: injectable (IV/IM) for systemic infections, ophthalmic solution and ointment (Gentak) for bacterial eye infections, and topical cream/ointment for skin infections. It is a generic medication — the injectable brand Garamycin is no longer widely marketed in the US.
FDA-approved uses include bacterial septicemia, meningitis, urinary tract infections, gastrointestinal infections including peritonitis, soft tissue and bone infections, and endocarditis (in combination with beta-lactams). The ophthalmic form treats bacterial conjunctivitis and corneal ulcers. The topical form treats superficial skin infections.
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Gentamicin works by entering bacterial cells and binding to the 30S ribosomal subunit — the part of the bacterium's machinery responsible for making proteins. Once bound, it causes the ribosome to misread genetic instructions (mRNA), producing defective proteins that disrupt the bacterial cell membrane. These membrane defects allow more gentamicin to flood in, creating a self-amplifying killing effect.
Gentamicin is bactericidal (kills bacteria rather than merely inhibiting growth) and its killing activity is concentration-dependent: higher peak drug levels result in faster and more complete bacterial killing. This is why modern dosing favors once-daily high-dose regimens (5–7 mg/kg) rather than smaller divided doses.
Gentamicin also has a post-antibiotic effect (PAE) — bacterial growth remains suppressed for hours after drug levels fall below the minimum inhibitory concentration. This PAE further supports extended-interval dosing and reduces toxicity compared to traditional every-8-hour dosing.
40 mg/mL — injectable solution
Standard vial concentration for IV/IM use. Dose calculated at 5-7 mg/kg for extended-interval dosing.
10 mg/mL — injectable solution
Lower concentration vial for IV/IM use, often used in pediatric dosing.
0.3% — ophthalmic solution (eye drops)
Gentak eye drops. 1-2 drops in affected eye(s) every 4 hours; up to every hour for severe infections.
0.3% — ophthalmic ointment
Gentak eye ointment. Half-inch ribbon to affected eye(s) 2-3 times daily.
0.1% — topical cream
Applied to affected skin area 3-4 times daily. Available in 15g tubes.
0.1% — topical ointment
Applied to affected skin area 3-4 times daily. Available in 15g tubes.
Gentamicin availability varies by formulation. Ophthalmic drops (Gentak) and topical cream are generally available at most retail pharmacies including CVS, Walgreens, and Walmart, though localized stock-outs do occur. Injectable gentamicin, used in hospital settings, is more vulnerable to supply disruptions — sterile injectable drugs are the category most frequently affected by FDA-tracked shortages due to concentrated manufacturing and low profit margins on generics.
As of 2026, gentamicin does not have an active national FDA shortage designation. However, regional back-orders for specific vial sizes and concentrations do occur. Findability score: 75/100 — generally available with occasional localized gaps.
If your pharmacy is out of gentamicin, medfinder calls pharmacies near you to find which ones have your medication in stock — and texts you the results. No more calling every pharmacy yourself.
Gentamicin is not a controlled substance and has no DEA schedule. Any licensed prescriber — physician, nurse practitioner, or physician assistant — can prescribe any formulation of gentamicin without additional registration or prescribing restrictions.
The following types of providers commonly prescribe gentamicin:
Infectious disease physicians — primary prescribers for injectable gentamicin in serious systemic infections
Hospitalists and intensivists (ICU physicians) — manage IV gentamicin for sepsis and ICU-level infections
Primary care physicians (PCPs) — common source for topical and ophthalmic gentamicin prescriptions
Ophthalmologists and optometrists — prescribe gentamicin ophthalmic for bacterial eye infections; ODs have full ophthalmic prescribing authority in all 50 states
Dermatologists — prescribe topical gentamicin for gram-negative skin infections
Emergency medicine physicians — initiate injectable gentamicin in the ER for acute serious infections
Nurse practitioners (NPs) and physician assistants (PAs) — can independently prescribe all gentamicin formulations in most US states
Telehealth is appropriate for prescribing ophthalmic and topical gentamicin. Platforms like Teladoc, MDLive, and Doctor on Demand regularly treat bacterial eye and skin infections remotely. Injectable gentamicin always requires in-person evaluation and hospital or infusion center administration.
No, gentamicin is not a controlled substance. It has no DEA schedule classification. Any licensed prescriber — physician, nurse practitioner, or physician assistant — can write a prescription for gentamicin without any DEA-specific registration, quantity limits, or special prescribing restrictions.
Gentamicin is a prescription-only medication because of its potential for serious side effects including nephrotoxicity and ototoxicity. Patients receiving injectable gentamicin require regular monitoring of kidney function and drug levels. Telehealth prescribing is appropriate for ophthalmic and topical formulations without restriction.
Injectable gentamicin carries a
Black Box Warning for nephrotoxicity (kidney damage) and ototoxicity (hearing and balance damage). These risks are highest with high doses, prolonged therapy, pre-existing kidney disease, and concurrent use of loop diuretics.
Common side effects (injectable):
Decreased urination or kidney function changes
Tinnitus (ringing in ears) — early ototoxicity warning sign
Dizziness or balance problems — vestibular toxicity
Nausea, vomiting
Pain at injection site
Lab abnormalities (elevated creatinine, low magnesium/potassium)
Serious side effects (seek immediate care):
Sudden hearing loss — can be permanent if not caught early
Severe dizziness or vertigo — vestibular damage
Markedly reduced urination, swollen legs — acute kidney injury
Muscle weakness, difficulty breathing — neuromuscular blockade
Severe allergic reaction (hives, throat tightening, facial swelling)
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Tobramycin
Closest aminoglycoside alternative with similar spectrum and dosing. Slightly more active against Pseudomonas aeruginosa. Available in injectable, ophthalmic (Tobrex), and inhaled forms (for cystic fibrosis). Nearly interchangeable with gentamicin in most clinical settings.
Amikacin
Broader-spectrum aminoglycoside reserved for gentamicin-resistant organisms. More expensive; requires different dosing (15-20 mg/kg/day). First choice when gentamicin/tobramycin resistance is confirmed or suspected.
Ciprofloxacin
Fluoroquinolone antibiotic with good gram-negative coverage available orally and IV. No ototoxicity risk. Rising resistance rates limit empirical use. Available in ophthalmic form (Ciloxan) as alternative to gentamicin eye drops.
Tobramycin ophthalmic (Tobrex)
For eye infections: the most direct ophthalmic alternative to Gentak. Same aminoglycoside class, similar gram-negative coverage, widely available at retail pharmacies.
Prefer Gentamicin? We can find it.
Furosemide (Lasix) / ethacrynic acid
majorMost dangerous combination. Both drugs are independently ototoxic — concurrent use dramatically increases risk of permanent hearing loss and nephrotoxicity.
Vancomycin
majorAdditive nephrotoxicity and ototoxicity. Combination sometimes clinically necessary but requires intensive monitoring of drug levels and kidney function.
Cisplatin
majorAdditive nephrotoxicity and ototoxicity. Avoid concurrent use; if required, close monitoring is essential.
Cidofovir
majorBoth drugs are severely nephrotoxic. Concurrent use is contraindicated — avoid this combination entirely.
Other aminoglycosides (tobramycin, amikacin, neomycin)
majorDo not combine gentamicin with other aminoglycosides — additive toxicity without meaningful additional benefit.
NSAIDs (ibuprofen, naproxen, indomethacin)
moderateReduce renal blood flow, increasing gentamicin accumulation in kidney tissue and raising nephrotoxicity risk. Avoid during gentamicin treatment; use acetaminophen instead.
Neuromuscular blocking agents
moderateGentamicin may potentiate neuromuscular blockade, prolonging paralysis. Relevant in surgical/ICU settings.
Amphotericin B
moderateAdditive nephrotoxicity. Monitor renal function closely if both agents are required.
Gentamicin is one of medicine's most durable and essential antibiotics. It has been treating serious bacterial infections for over six decades and remains a critical tool against gram-negative organisms — including drug-resistant Pseudomonas aeruginosa — that other antibiotics cannot reliably cover. Its ophthalmic and topical formulations are affordable, widely available, and effective for everyday eye and skin infections.
The primary challenges with gentamicin in 2026 are availability for the injectable form (as part of the broader sterile injectable supply vulnerability) and the need for careful monitoring to avoid its serious toxicities. Patients and providers who understand these issues are better equipped to use gentamicin safely and effectively.
If you are having trouble finding gentamicin at your pharmacy, medfinder can help you locate it quickly. Enter your medication, dosage, and ZIP code — medfinder calls local pharmacies and texts you which ones have it in stock.
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