TOBRAMYCIN SULFATE (PHARMACY BULK)
Clinical safety rating: avoid
Other nephrotoxic or ototoxic drugs increase risk of toxicity Monitor peak and trough levels to minimize risk of nephrotoxicity and ototoxicity.
Aminoglycoside antibiotic that binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis, leading to bacterial cell death. Bactericidal against Gram-negative aerobes.
| Metabolism | Primarily excreted unchanged by the kidneys via glomerular filtration. Minimal hepatic metabolism. |
| Excretion | Primarily renal excretion of unchanged drug via glomerular filtration; >90% of dose recovered in urine within 24 hours. Biliary/fecal elimination is minimal (<1%). |
| Half-life | Terminal elimination half-life of 2–3 hours in patients with normal renal function; prolonged to 24–60 hours in anuria/end-stage renal disease. In neonates, half-life may be 4–12 hours depending on gestational age. |
| Protein binding | 30–40% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is 0.25–0.40 L/kg, approximating extracellular fluid volume. Increased Vd in edematous states (e.g., ascites, burns) and decreased in dehydrated patients. |
| Bioavailability | Oral bioavailability <1%; administered parenterally (IM/IV) for systemic effects. Nebulized tobramycin yields negligible systemic absorption (<1% of dose). |
| Onset of Action | Intramuscular or intravenous: Onset of action occurs within 30–60 minutes after administration, with peak serum concentrations achieved by 30 minutes after IV infusion or 60 minutes after IM injection. Nebulized: Onset of action is within 15–30 minutes for local pulmonary effects. |
| Duration of Action | Duration of action is approximately 6–8 hours for systemic administration, limited by rapid renal clearance; serum concentrations should be monitored to maintain therapeutic levels. Nebulized tobramycin provides sustained local effects in the lungs for up to 12 hours after a single dose, but systemic levels are negligible. |
| Molecular Weight | 467.5 |
5-7 mg/kg IV q24h (extended-interval) or 1.5-2.5 mg/kg IV q8h (traditional dosing) for serious Gram-negative infections; adjust based on therapeutic drug monitoring.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 10-50 mL/min: prolong interval (e.g., q24-48h). CrCl <10 mL/min: q48-72h or per serum levels. Use lower traditional doses if extended-interval contraindicated. Monitor peak and trough. |
| Liver impairment | No dose adjustment required for hepatic impairment. Pharmacokinetics not significantly altered in Child-Pugh A, B, or C. However, monitor renal function as underlying disease may co-exist. |
| Pediatric use | Neonates: 2.5 mg/kg IV q12h (postnatal age <7 days) or q8h (7-28 days). Infants/children: 2.5 mg/kg IV q8h (traditional) or 5-7 mg/kg IV q24h (extended-interval). Cystic fibrosis: higher doses (7-10 mg/kg IV q24h). Adjust per TDM. |
| Geriatric use | Use lower initial doses based on ideal body weight and renal function. Monitor renal function (eGFR) and serum concentrations closely. Extended-interval dosing may be preferred with careful trough monitoring. |
| 1st trimester | Avoid use during first trimester unless benefit outweighs risk; potential for ototoxicity and nephrotoxicity. |
| 2nd trimester | Use only if clearly needed; risk of fetal harm due to aminoglycoside toxicity. |
| 3rd trimester | Use only if clearly needed; risk of fetal auditory and renal toxicity. |
Clinical note
Other nephrotoxic or ototoxic drugs increase risk of toxicity Monitor peak and trough levels to minimize risk of nephrotoxicity and ototoxicity.
| FDA category | Positive |
| Placental transfer | Crosses placenta; fetal serum levels approximately 15-50% of maternal levels. |
| Breastfeeding |
■ FDA Black Box Warning
Aminoglycosides, including tobramycin, are associated with nephrotoxicity and ototoxicity (vestibular and auditory). Risk is higher with renal impairment, prolonged use, high doses, or concurrent ototoxic/nephrotoxic drugs. Neurotoxicity (neuromuscular blockade) may occur, especially with anesthetics or neuromuscular blocking agents. Avoid use in patients with hypersensitivity to aminoglycosides.
| Common Effects | Nephrotoxicity |
| Serious Effects |
Hypersensitivity to tobramycin or any aminoglycosideMyasthenia gravis (risk of worsening neuromuscular blockade)
| Precautions | Other nephrotoxic or ototoxic drugs increase risk of toxicity Monitor peak and trough levels to minimize risk of nephrotoxicity and ototoxicity. |
| Food/Dietary | No specific food interactions. Maintain adequate hydration. Avoid excessive salt intake if renal impairment exists. Alcohol may increase risk of dizziness. |
Loading safety data…
| Poorly excreted into breast milk; minimal oral bioavailability in infant. Caution due to potential alteration of infant gut flora and theoretical risk of ototoxicity/nephrotoxicity. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Aminoglycosides cross the placenta. First trimester: No well-documented increased risk of major malformations, but data limited. Second and third trimesters: Potential for fetal ototoxicity (eighth cranial nerve damage) and nephrotoxicity, especially with prolonged or high-dose therapy. Risk of bilateral congenital deafness reported. |
| Fetal Monitoring | Maternal: Renal function (serum creatinine, BUN), urinalysis, audiometry at baseline and periodically, serum drug levels (trough and peak) to avoid toxicity. Fetal: Ultrasound monitoring for fetal growth and amniotic fluid volume if used for prolonged periods; consider newborn hearing screen after delivery if exposure in late pregnancy. |
| Fertility Effects | In animal studies, no impairment of fertility was observed. Human data limited. No known effect on spermatogenesis or oogenesis at therapeutic doses. Systemic toxicity (nephrotoxicity, ototoxicity) may indirectly affect general health and fertility. |
| Clinical Pearls | Tobramycin sulfate is an aminoglycoside antibiotic used for serious Gram-negative infections. Monitor renal function and drug levels (peak and trough) due to nephrotoxicity and ototoxicity risk. Adjust dosing based on creatinine clearance. Avoid concomitant use with other nephrotoxic drugs (e.g., vancomycin, loop diuretics). For extended-interval dosing, trough levels should be <1 mcg/mL. Inhaled tobramycin is used for Pseudomonas in cystic fibrosis; monitor bronchospasm. |
| Patient Advice | Take this medication exactly as prescribed; do not skip doses or double up. · Drink plenty of fluids to prevent dehydration and reduce kidney strain. · Report any hearing loss, ringing in ears, dizziness, or changes in urination immediately. · Avoid taking other medications without consulting your doctor, especially painkillers like NSAIDs. · If you have cystic fibrosis, use inhaled tobramycin with a nebulizer; clean equipment after each use. |