Risk Summary
Aminoglycosides can cause fetal harm. Published literature reports that use of streptomycin, an aminoglycoside, can cause total, irreversible, bilateral congenital deafness when administered to a pregnant woman [Warnings and Precautions (5.5)]. Although there are no available data on TOBRAMYCIN INHALATION SOLUTION PAK use in pregnant women to inform a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes, systemic absorption of tobramycin following inhaled administration is expected to be minimal [see Clinical Pharmacology (12.3)]. There are risks to the mother associated with cystic fibrosis in pregnancy (see Clinical Considerations).
In animal reproduction studies with subcutaneous administration of tobramycin in pregnant rats and rabbits during organogenesis there were no adverse developmental outcomes; however, ototoxicity was not evaluated in the offspring from these studies (see Data). Advise pregnant women of the potential risk to a fetus.
The estimated background risk of major birth defects and miscarriage for the indicated populations are unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
Clinical Considerations
Disease-Associated Maternal and/or Embryo/Fetal Risk
Cystic fibrosis may increase the risk for preterm delivery.
Data
Animal Data
No reproductive toxicity studies have been conducted with tobramycin inhalation solution. However, subcutaneous administration of tobramycin at doses of up to 100 (rat) or 20 (rabbit) mg/kg/day during organogenesis was not associated with adverse developmental outcomes. Subcutaneous doses of tobramycin ≥40 mg/kg/day were severely maternally toxic to rabbits and precluded the evaluation of adverse developmental outcomes. Ototoxicity was not evaluated in offspring during non-clinical reproductive toxicity studies with tobramycin.
Risk Summary
There are no data on the presence of tobramycin inhalation solution in either human or animal milk, the effects on the breastfed infant, or the effects on milk production. Limited published data on other formulations of tobramycin in lactating women indicate that tobramycin is present in human milk. However, systemic absorption of tobramycin following inhaled administration is expected to be minimal [see Clinical Pharmacology (12.3)]. Tobramycin may cause alteration in the intestinal flora of the breastfeeding infant (see Clinical Considerations). The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for TOBRAMYCIN INHALATION SOLUTION PAK and any potential adverse effects on the breastfed infant from TOBRAMYCIN INHALATION SOLUTION PAK or from the underlying maternal condition.
Clinical Considerations
Tobramycin may cause intestinal flora alteration. Advise a woman to monitor the breastfed infant for loose or bloody stools and candidiasis (thrush, diaper rash).
Absorption
Tobramycin inhalation solution contains tobramycin, a cationic polar molecule that does not readily cross epithelial membranes. 1 The bioavailability of tobramycin inhalation solution may vary because of individual differences in nebulizer performance and airway pathology.2 Following administration of tobramycin inhalation solution, tobramycin remains concentrated primarily in the airways.
Sputum Concentrations
Ten minutes after inhalation of the first 300 mg dose of tobramycin inhalation solution, the average concentration of tobramycin was 1237 mcg/g (ranging from 35 to 7414 mcg/g) in sputum. Tobramycin does not accumulate in sputum; after 20 weeks of therapy with the tobramycin inhalation solution regimen, the average concentration of tobramycin at ten minutes after inhalation was 1154 mcg/g (ranging from 39 to 8085 mcg/g) in sputum. High variability of tobramycin concentration in sputum was observed. Two hours after inhalation, sputum concentrations declined to approximately 14% of tobramycin levels at ten minutes after inhalation.
Serum Concentrations
The average serum concentration of tobramycin one hour after inhalation of a single 300 mg dose of tobramycin inhalation solution by cystic fibrosis patients was 0.95 mcg/mL. After 20 weeks of therapy on the tobramycin inhalation solution regimen, the average serum tobramycin concentration one hour after dosing was 1.05 mcg/mL.
Distribution
Following administration of tobramycin inhalation solution, tobramycin remains concentrated primarily in the airways. Binding of tobramycin to serum proteins is negligible.
Elimination
Metabolism
Tobramycin is not metabolized.
Excretion
The elimination half-life of tobramycin from serum is approximately 2 hours after intravenous (IV) administration. Assuming tobramycin absorbed following inhalation behaves similarly to tobramycin following IV administration, systemically absorbed tobramycin is eliminated principally by glomerular filtration. Unabsorbed tobramycin, following tobramycin inhalation solution administration, is likely eliminated primarily in expectorated sputum.
Mechanism of Action
Tobramycin is an aminoglycoside antibacterial produced by Streptomyces tenebrarius. It acts primarily by disrupting protein synthesis, leading to altered cell membrane permeability, progressive disruption of the cell envelope, and eventual cell death. 3
Tobramycin has in vitro activity against Gram-negative bacteria including P. aeruginosa. It is bactericidal in vitro at peak concentrations equal to or slightly greater than the minimum inhibitory concentration.
Resistance
Treatment for 6 months with tobramycin inhalation solution in two clinical studies did not affect the susceptibility of the majority of P. aeruginosa isolates tested; however, increased minimum inhibitory concentrations (MICs) were noted in some patients. The clinical significance of this information has not been clearly established in the treatment of P. aeruginosa in cystic fibrosis patients [see Clinical Studies (14)].
Susceptibility Testing
Interpretive criteria for inhaled antibacterial products are not defined. The in vitro antimicrobial susceptibility test methods used for parenteral tobramycin therapy can be used to monitor the susceptibility of P. aeruginosa isolated from cystic fibrosis patients. 4,5,6 If decreased susceptibility is noted, the results should be reported to the clinician. Susceptibility breakpoints established for parenteral administration of tobramycin do not apply to aerosolized administration of tobramycin inhalation solution. The relationship between in vitro susceptibility test results and clinical outcome with tobramycin inhalation solution therapy is not clear. A single sputum sample from a cystic fibrosis patient may contain multiple morphotypes of Pseudomonas aeruginosa and each morphotype may have a different level of in vitro susceptibility to tobramycin.
For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.
Difficulty Breathing
Advise patients to inform their physicians if they experience shortness of breath or wheezing after administration of tobramycin inhalation solution. Tobramycin inhalation solution can cause a narrowing of the airway [see Warnings and Precautions (5.1)].
Hearing Loss
Advise patients to inform their physician if they experience ringing in the ears, dizziness, or any changes in hearing because tobramycin inhalation solution has been associated with hearing loss [see Warnings and Precautions (5.2)].
Kidney Damage
Advise patients to inform their physician if they have any history of kidney problems because tobramycin inhalation solution is in a class of drugs that have caused kidney damage [see Warnings and Precautions (5.3)].
Embryo-Fetal Toxicity:
Advise pregnant women that aminoglycosides can cause irreversible congenital deafness when administered to a pregnant woman [see Warnings and Precautions (5.5) and Use in Specific Populations (8.1)].
Lactation:
Advise a woman to monitor their breastfed infants for diarrhea and/or bloody stools [see Use in Specific Populations (8.2)].
Additional Information
PARI LC PLUS® Reusable Nebulizer: 1-800-327-8632
DeVilbiss® Pulmo-Aide® Air Compressor: 1-800-338-1988
TOBRAMYCIN INHALATION SOLUTION PAK: 1-877-236-7239
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