Antibiotic-Steroid Combinations

Concise summaries of common antibiotic-steroid combination eye drops and medications used in optometric practice in Singapore, including practical guidance on pharmacology, dosing, patient selection, and monitoring.

Last updated: March 2026

What are antibiotic-steroid combination eye drops?

Antibiotic-steroid combination eye drops are fixed-dose topical ophthalmic preparations that simultaneously deliver an antimicrobial agent and a corticosteroid to the ocular surface. They are designed for situations where both bacterial infection control and suppression of the accompanying inflammatory response are clinically required — most commonly following anterior segment surgery, or in infected inflammatory conditions of the eyelid and conjunctiva.

The antibiotic component targets the causative pathogen and reduces the risk of secondary microbial colonisation, while the steroid component limits tissue damage, discomfort, and scarring from the inflammatory cascade. The combination in a single bottle also improves patient adherence compared to separate instillations.^[1]

Drug components in common combinations

Antibiotic components

Tobramycin, gentamicin, neomycin, framycetin, polymyxin B — all aminoglycosides or related antibacterials with broad gram-positive and gram-negative coverage.

Steroid components

Dexamethasone, prednisolone, loteprednol, betamethasone — ranging from moderate (loteprednol) to potent (dexamethasone, betamethasone) anti-inflammatory potency.

Formulations available

Ophthalmic suspension (shake before use), solution, and ointment (nocte use or for eyelid margin application).

Preservative systems

Most contain benzalkonium chloride (BAK); some newer formulations use alternative preservatives. Advise removal of soft contact lenses before instillation.

Who are they for?

Antibiotic-steroid combinations are indicated for a specific subset of patients where concurrent bacterial risk and significant inflammation coexist. They should not be used as a first-line agent for uncomplicated bacterial conjunctivitis (where a plain antibiotic suffices) or for inflammation alone (where a plain steroid is more appropriate and less likely to mask a primary infection).

Appropriate patient profiles

Post-operative anterior segment

After cataract surgery, pterygium excision, or corneal procedures — prevents wound infection while controlling post-surgical inflammation.

Infected blepharoconjunctivitis

Staphylococcal lid disease with significant conjunctival inflammation unresponsive to plain antibiotic therapy.

Corneal ulcer (bacterial, mild–moderate)

Where simultaneous inflammation control is needed after culture is taken and microbial keratitis is of low severity; specialist co-management is advised.

Traumatic iritis with surface infection risk

Anterior uveitis following penetrating or blunt trauma where surface bacterial contamination is suspected.

Contraindications — do not use in:

Active or suspected viral keratitis (herpes simplex, herpes zoster) — steroid component will potentiate viral replication and worsen stromal disease.
Fungal keratitis or suspected Acanthamoeba — steroids suppress the immune response needed to contain these organisms.
Known neomycin or framycetin contact allergy — risk of severe ocular surface reaction.
Uncontrolled glaucoma — corticosteroid-induced IOP elevation may cause rapid progression.

When should they be prescribed?

Post-operative prophylaxis and treatment

The most common indication in Singapore is post-cataract surgery management. Tobradex suspension is frequently prescribed by ophthalmologists starting on day one post-operatively, typically QID for the first week then tapered over 3–4 weeks. Optometrists co-managing post-operative patients should be familiar with the standard taper regimens and monitoring expectations.^[2]

Acute infected inflammation

When an acute bacterial infection is accompanied by significant inflammation — confirmed by culture or high clinical suspicion — a combination drop can streamline treatment. Duration should be the minimum necessary; typically 7–14 days for acute presentations, with IOP review at 2 weeks if continued beyond this.

When to escalate or refer

If symptoms worsen after 48–72 hours of treatment, if a dendritic corneal lesion is identified, or if there is any suspicion of fungal or protozoal keratitis, cease the combination drop immediately and refer urgently. Steroid masking of an atypical infection is a significant risk if the diagnosis is incorrect.

Indication	Preferred agent	Typical duration
Post-cataract surgery	Tobradex QID then taper	4 weeks (standard taper)
Post-pterygium excision	Tobradex or Maxitrol QID	2–4 weeks
Bacterial blepharoconjunctivitis + inflammation	Tobradex or Sofradex QID	7–10 days
Mild bacterial keratitis (post-culture)	Tobradex hourly then taper	Specialist-directed
Steroid-responder at risk	Zylet (loteprednol + tobramycin)	As above with IOP checks

Where are they available in Singapore?

All antibiotic-steroid combination eye drops are classified as Prescription-Only Medicines (POM) in Singapore under the Medicines Act, regulated by the Health Sciences Authority (HSA). They require a prescription from a registered medical practitioner — optometrists in Singapore do not hold prescribing rights for therapeutic medications.

Scope of practice — Singapore optometrists

Under the Optometrists and Opticians Act (Cap. 213A), Singapore-registered optometrists are authorised to examine eyes, assess visual function, and prescribe optical appliances (spectacles and contact lenses). They do not have the authority to prescribe, supply, or administer therapeutic medications, including antibiotic-steroid eye drops. Any patient requiring these medications must be referred to a medical doctor — typically an ophthalmologist or a GP with ophthalmic experience.^[3]

Ophthalmologists (primary prescribers): Specialist eye doctors at SNEC, NUH Eye Institute, TTSH, and private ophthalmology clinics prescribe these drops post-operatively and for sight-threatening infections. Most post-cataract prescriptions originate here.
General practitioners: GPs may prescribe milder antibiotic-steroid combinations (e.g., Tobradex) for uncomplicated infected blepharoconjunctivitis; more complex or corneal presentations should be referred to an ophthalmologist.
Role of the optometrist: Singapore optometrists play an important role in detecting anterior segment disease, monitoring post-operative patients under shared-care arrangements, and identifying when a prescription medication is needed — but must refer to a doctor for the actual prescription.
HSA product verification: Current registered products and approved indications can be confirmed at hsa.gov.sg — Product Registration search. Always verify current registration status, as product availability may change.^[4]

Why use a combination rather than separate drops?

When both antimicrobial and anti-inflammatory treatment are simultaneously required, a fixed combination offers practical advantages over separate preparations — but comes with trade-offs that require clinical judgement.

Improved adherence

Single bottle reduces instillation burden, improving compliance — especially important in post-operative patients managing multiple drops.

Simultaneous action

Both drug components reach the ocular surface together, ensuring anti-infective and anti-inflammatory effects are timed identically.

Reduced exposure to preservatives

One bottle instead of two means less total BAK exposure to the ocular surface — relevant for already compromised post-operative epithelium.

Trade-off: less flexibility

Fixed-ratio combinations cannot be titrated independently — if the infection resolves but inflammation persists, switching to a plain steroid is required.

A key principle: the steroid component must never be used to suppress inflammation before ruling out a viral, fungal, or parasitic etiology. If the diagnosis is uncertain, culture and sensitivity testing before initiating a combination drop is best practice — particularly for any corneal involvement.^[4]

How to use antibiotic-steroid eye drops — patient instructions and monitoring

Instillation technique

Wash hands before use. Shake suspension bottles thoroughly before each instillation.
Tilt head back and gently pull down the lower eyelid to form a pocket.
Instil one drop into the lower fornix; avoid touching the dropper tip to the eye or any surface.
Close the eye gently and apply nasolacrimal occlusion (finger pressure at inner canthus) for 1–2 minutes to maximise ocular contact and reduce systemic drainage.
If other eye drops are also prescribed, wait at least 5 minutes between instillations, applying least viscous drops first.
Do not use while wearing soft contact lenses; reinsert only after 15+ minutes if using BAK-preserved formulations.

Tapering schedule (standard post-operative example)

Week	Dosing frequency	Clinical goal
Week 1	QID (4× daily)	Control acute inflammation and infection risk
Week 2	TID (3× daily)	Maintain anti-inflammatory effect during healing
Week 3	BD (2× daily)	Step-down; monitor IOP
Week 4	OD (once daily) then stop	Avoid rebound inflammation

Taper schedules vary by surgeon preference and clinical response. Always follow the prescribing clinician's protocol.

Monitoring requirements

IOP: Check at 2-week mark for any patient on steroid-containing drops. Baseline IOP before starting is strongly recommended. Discontinue or switch to loteprednol formulation if IOP rises >5 mmHg above baseline.
Slit-lamp examination: Assess corneal epithelial integrity, anterior chamber activity, and lid margin status at each review visit.
Infection signs: Monitor for worsening discharge, increasing infiltrate, or new corneal haze — indicators of treatment failure or misdiagnosis requiring urgent referral.
Prolonged use: Avoid exceeding 4–6 weeks without specialist review. Long-term use risks posterior subcapsular cataract formation and steroid-induced glaucoma.

Clinical reminder — suspension formulations

Tobradex and similar suspensions must be shaken thoroughly before each use. Failure to do so results in inconsistent drug delivery — the patient may receive predominantly one component (antibiotic or steroid) rather than the intended fixed-ratio combination.

Common antibiotic-steroid eye drops in Singapore

All agents listed are registered with HSA Singapore or available through licensed importers. Verify current product registration at hsa.gov.sg before prescribing.

Brand (Generic)	Mechanism	Dosing	Min. Age	Side Effects	Clinical Notes
Tobradex Tobramycin 0.3% + Dexamethasone 0.1% POM	Aminoglycoside antibiotic + corticosteroid	Suspension: 1–2 drops every 4–6 h; taper over 2–4 weeks. Ointment: apply 2–3× daily.	≥2 years	Raised IOP, cataract, delayed wound healing, secondary infection	Most widely prescribed combination in Singapore; suitable for post-operative inflammation with infection risk
Maxitrol Neomycin 3500 IU + Polymyxin B 6000 IU + Dexamethasone 0.1% POM	Dual-spectrum antibiotic (gram +/−) + corticosteroid	Drops: 1–2 drops every 4–6 h; Ointment: apply 3–4× daily or nocte	≥2 years	Neomycin contact sensitisation, raised IOP, secondary infection	Avoid in patients with known neomycin allergy; useful for mixed gram-positive/negative infections with inflammation
Zylet Tobramycin 0.3% + Loteprednol 0.5% POM	Aminoglycoside + retrometabolic corticosteroid	1–2 drops every 4–6 h for 24–48 h then QID; taper as indicated	≥2 years	Lower IOP-raising risk vs. dexamethasone combinations; mild stinging	Preferred when IOP risk is elevated (steroid responders, glaucoma suspects); limited availability in SG — confirm with supplier
Ducressa Levofloxacin 0.5% + Dexamethasone 0.1% POM	Fluoroquinolone antibiotic + corticosteroid	1 drop 4× daily for first week, then 1 drop twice daily for second week; often used post-cataract surgery	≥18 years	Raised IOP, cataract (prolonged use), ocular irritation, secondary infection, fluoroquinolone resistance risk	Indicated for prevention and treatment of inflammation and infection after cataract surgery; convenient dosing; broad-spectrum fluoroquinolone coverage
Dexa-Gentamicin Gentamicin 0.3% + Dexamethasone 0.1% POM	Aminoglycoside antibiotic + corticosteroid	1–2 drops every 4–6 h; taper over 1–2 weeks	≥2 years (supervised use)	Raised IOP, cataract, delayed wound healing, secondary infection; gentamicin ototoxicity/nephrotoxicity rare with topical use	Long-established gentamicin-based combination; useful for bacterial infections with anterior segment inflammation; monitor for gentamicin sensitivity

Legend

POMPrescription Only Medicine — Sold or supplied to the public on prescription only.

PPharmacy Medicine — Sold or supplied from any licensed retail pharmacy under pharmacist supervision.

OTCGeneral Sales List (GSL) — Sold or supplied to the public without restriction.

Dosing reflects standard adult doses unless noted. Always refer to the approved product insert for full prescribing information. QID = four times daily, TID = three times daily, BD = twice daily, OD = once daily.

References

[1] Lemley CA, Han DP. Endophthalmitis: a review of current evaluation and management. Retina. 2007;27(6):662–680.
[2] Tan DT, et al. Cataract surgery guidelines for Singapore. Singapore Med J. 2018;59(10):510–516.
[3] Health Sciences Authority Singapore. Product Registration Search. Available at: hsa.gov.sg (accessed March 2026).
[4] O'Brien TP. Emerging guidelines for use of NSAID therapy to optimize cataract surgery patient care. Curr Med Res Opin. 2005;21(7):1131–1137.
[5] Wilhelmus KR. Indecision about corticosteroids for bacterial keratitis: an evidence-based update. Ophthalmology. 2002;109(5):835–842.
[6] Singapore Optometric Association. Therapeutic Prescribing Guidelines for Optometrists, 2nd ed. SOA, 2021.

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