Tobramycin

TOBREX

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Pronunciation: toe-bra-MYE-sin

Tobramycin ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Tobramycin ballicule

What it isAminoglycoside inhibiting the 30S ribosomal subunit; Gram-negative and pseudomonal infection, inhaled in cystic fibrosis.

Why this oneBetter antipseudomonal activity than gentamicin, and the inhaled route delivers high airway concentrations with little systemic exposure.

What limits itNephrotoxicity and irreversible ototoxicity, so levels and function are monitored. Once-daily dosing exploits the post-antibiotic effect.

Tobramycin molecular structure (skeletal formula) — Molecular structure: Tobramycin

FDA-approved for

Pseudomonas infections (1975)
cystic fibrosis (inhaled) (1997)

FDA label

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FDA dosing	Population	Start	Target	Max
External infections of the eye and adnexa (susceptible bacteria) — mild to moderate	Adults & children	½-inch ribbon in affected eye(s) BID–TID		TID
External infections of the eye and adnexa (susceptible bacteria) — severe	Adults & children	½-inch ribbon in affected eye(s) q3–4h until improvement	Reduce frequency before discontinuation	q3–4h

Renal Undefined

Hepatic Undefined

Instructions

Ophthalmic only — not for injection into the eye
Pull lower lid down to form a pocket; place ~½ inch in pocket; do not let tube tip touch the eye; look down before closing
Taper frequency before stopping (severe infection)

Available strengths

drops 0.3 %
ointment 0.3 %
cap 28 mg
powder 28 mg
sol 300 mg/4 mL
inhaler 300 mg/5 mL
inj 10, 40 mg/mL

Cautions

Not for injection into the eye
Sensitivity to topical aminoglycosides (local to generalized reactions incl. anaphylaxis) — discontinue

Adverse reactions

Hypersensitivity (<3%)
Lid itching and swelling (<3%)
Conjunctival erythema (<3%)

Pregnancy No fetal harm in animals at up to 33× human systemic dose; no adequate human studies — use only if clearly needed.

Lactation Decide whether to discontinue nursing or the drug, considering importance to the mother.

Cost

Tobramycin (TOBREX)

Strength		#/mo	generic $/unit	CostPlus
0.3 %	drops	per unit		not offered
0.3 %	ointment	per unit		not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. Tobramycin is dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

Generic entry1984

⚠ BOXED WARNINGS

Nephrotoxicity and ototoxicity
Neuromuscular blockade

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk2 / 4

Legacy pregnancy categoryD

Defining liabilityUsually well tolerated at replacement doses; excessive dosing can cause agent-specific metabolic or organ toxicity.

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