5.1 Farmakodynamika
Pharmacotherapeutic group: Antibacterials for systemic use, Aminoglycoside antibacterials. ATC code: J01GB01
Mechanism of action Tobramycin is an aminoglycoside antibiotic produced by Streptomyces tenebrarius. It acts primarily by disrupting protein synthesis leading to altered cell membrane permeability, progressive disruption of the cell d envelope and eventual cell death. It is bactericidal at concentrations equal to or slightly greater than e inhibitory concentrations. s i Breakpoints r Established susceptibility breakpoints for parenteral administration of tobramycin are inapproopriate in the aerosolised administration of the medicinal product. Sputum of cystic fibrosis patients exhibits an inhibitory h action on the local biological activity of nebulised aminoglycosides. This necessitates sputum concentrations t following treatment with aerosolised tobramycin to be ten to twentyfive-fold above the Minimum Inhibitory u Concentration (MIC) for both P. aeruginosa growth suppression and control of bactericidal activity. In a controlled clinical trials, 97% of patients receiving tobramycin nebuliser solution achieved sputum concentrations 10-fold of the highest P. aeruginosa MIC cultured from the patient and 95% of patients r receiving tobramycin nebuliser solution achieved 25-fold of the highest MIC. e g Susceptibility In the absence of conventional susceptibility breakpoints for the nnebulised route of administration, caution must be exercised in defining organisms as susceptible or insusceoptible to nebulised tobramycin. l In clinical studies with TOBI, most patients with P. aeruginosa isolates with tobramycin MICs < 128 µg/ml o at baseline showed improved lung function following treatment with TOBI. Patients with a P. aeruginosa isolate with MIC 128 µg/ml at baseline are less liknely to show a clinical response. However, seven of 13 patients (54%) in the placebo-controlled trials who acquired isolates with MICs of 128 µg/ml while using t TOBI had improvement in pulmonary function. c Based upon in-vitro data and/or clinical trial experience, the organisms associated with pulmonary infections u in CF may be expected to respond to Vantobra therapy as follows: d
|
o |
| Susceptible |
Pseudomonas aeruginosa r Haemophilus influenzae Staphylocopus aureuscc |
|
l |
| Insusceptible |
Bura lderia cepaciakho Stenotrophomonas maltophilia n i Alcaligenes xylosoxidans |
| c |
|
Treatment with the 28-days on and 28-days off dose regimen in clinical studies showed a small but clear i increase idn tobramycin, amikacin and gentamicin MICs for P. aeruginosa isolates tested. Each additional 6 months of treatment resulted in incremental increases similar in magnitude to that observed in the 6 months e of controlled studies. The most prevalent aminoglycoside resistance mechanism seen in P. aeruginosa Mitsoolaallteadmfrinoomglcyhcroosnidiceasl.lyPi.nafeecrtuegdinCoFsapiastoielanttesdisfriommpeCrmFepabatiileitnyt,sdheafisneadlsobybeaegnensheorawl nlactok eoxfhsiubsitceapdtaibpitliivtye aremminoovgedly.coside resistance that is characterised by a reversion to susceptibility when the antibiotic is
Other information There is no evidence that patients treated with up to 18 months with tobramycin nebuliser solution were at a greater risk for acquiring B. cepacia, S. maltophilia or A. xylosoxidans, than would be expected in untreated patients. Aspergillus species were more frequently recovered from the sputum of treated patients; however, clinical sequelae such as Allergic Bronchopulmonary Aspergillosis (ABPA) were reported rarely and with similar frequency as in the control group.
Aerosol characteristics
Table 2: Comparative performance data for the clinical test and reference batches: Vantobra /Tolero nebuliser handset1, and TOBI/PARI LC PLUS2.
| Performance parameter/ Drug/Device combination* |
Vantobra/Tolero |
TOBI/PARI LC PLUS |
| Total Drug Delivered [mg±SD] |
96 ± 4.4 |
101 ± 8.5 |
| Fine Particle Mass < 5 µm [mg±SD] |
72 ± 6.5 |
65 ± 7.1 |
| Drug Delivery Rate [mg/min] |
27 ± 5.0 |
7 ± 0.9 |
| Mass Median Aerodynamic Diameter [µm ± SD] |
3.8 ± 0.3 |
3.6 ± 0.4 |
| Geometric Standard Deviation ±SD |
1.5 ± 0.0 |
2.3 ± 0.2 |
| Nebulisation Time [min] |
3.9 ± 0.6 |
15.3 ± 0.6 |
d e s i r o h t *Results from breath simulation and cascade impactor measurements. u 1 connected with an eBase controller or eFlow rapid controller a 2 connected with a PARI Boy SX compressor The drug delivery rate of Vantobra with the Tolero nebuliser is independent ofrthe breathing pattern applied i.e. adult or child in contrast to the PARI LC PLUS nebuliser. e g Clinical efficacy and safety n Limited data from one controlled clinical study over one treatmoent cycle indicate that the improvement in lung function was maintained above baseline during the 28-dayloff-treatment period. As a result of study 12012.101, lung function improvement FEV % predicted relative to baseline increased o 1 by 8.2 ± 9.4% under Vantobra and by 4.8 ± 9.6% under the reference therapy in the first treatment cycle n showing non-inferior (p=0.0005) efficacy. CFU reduction as an indicator for suppression of P. aeruginosa was comparable for Vantobra and the reference prtoduct. c u
5.2 Farmakokinetyka
d Absorption and distribution o r The systemic exposure to tobpramycin after inhalation of Vantobra is expected to emerge primarily from the inhaled portion of the medicinal product as tobramycin is not absorbed to any appreciable extent when l administered via the oraal route. Inhalation of nebulised tobramycin produces high sputum concentrations and low plasma levels. n i For comparativce aerosol data please refer to Table 2 in section 5.1 i At the endd of a 4-weeks dosing cycle of Vantobra (170 mg/1.7 ml twice daily) in cystic fibrosis patients, maximeum tobramycin plasma concentrations (Cmax) of 1.27 ± 0.81 µg/ml were reached at approximately one hour after inhalation. Sputum concentrations were higher and more variable with Cmax of 1,951 + 2,187 M µg/g. After administering a single dose of Vantobra 170 mg to healthy volunteers Cmax of 1.1 + 0.4 µg/ml were reached after a tmax of approximately 4 hours.
Distribution Less than 10% of tobramycin is bound to plasma proteins.
Biotransformation Tobramycin is not metabolised and is primarily excreted unchanged in the urine.
Elimination
The elimination of tobramycin administered by the inhalation route has not been studied.
Following intravenous administration, systemically absorbed tobramycin is eliminated by glomerular filtration. The elimination half-life of tobramycin from serum is approximately 2 hours.
Unabsorbed tobramycin following administration by inhalation is probably eliminated primarily in expectorated sputum.
d
5.3 Przedkliniczne dane o bezpieczeństwie
e s Non-clinical data reveal that the main hazard for humans, based on conventional studies of safety i pharmacology, repeated dose toxicity, genotoxicity, carcinogenic potential and toxicity to reprodurction and development, consists of renal toxicity and ototoxicity. In repeated dose toxicity studies it hasobeen shown that target organs of toxicity are the kidneys and vestibular/cochlear functions. In general, toxicity is seen at h higher systemic tobramycin levels than are achievable by inhalation of the recommended clinical dose. t u No reproduction toxicology studies have been conducted with tobramycin administered by inhalation. a Subcutaneous administration at doses of 100 mg/kg/day in rats and the maximum tolerated dose of 20 mg/kg/day in rabbits during organogenesis was not teratogenic. Teratogenicity could not be assessed at r higher parenteral doses in rabbits as they induced maternal toxicity and abortion. Based on available data e from animals a risk of toxicity (e.g. ototoxicity) at prenatal exposure levels cannot be excluded. Tobramycin g did not impair fertility in male or female rats at subcutaneous doses up to 100 mg/kg/day. n o