Ricardo J. Gonzalez-Rothi

Inspiratory muscle strength training improves weaning outcome in failure to wean patients: a randomized trial

IntroductionMost patients are readily liberated from mechanical ventilation (MV) support, however, 10% - 15% of patients experience failure to wean (FTW). FTW patients account for approximately 40% of all MV days and have significantly worse clinical outcomes. MV induced inspiratory muscle weakness has been implicated as a contributor to FTW and recent work has documented inspiratory muscle weakness in humans supported with MV.MethodsWe conducted a single center, single-blind, randomized controlled trial to test whether inspiratory muscle strength training (IMST) would improve weaning outcome in FTW patients. Of 129 patients evaluated for participation, 69 were enrolled and studied. 35 subjects were randomly assigned to the IMST condition and 34 to the SHAM treatment. IMST was performed with a threshold inspiratory device, set at the highest pressure tolerated and progressed daily. SHAM training provided a constant, low inspiratory pressure load. Subjects completed 4 sets of 6-10 training breaths, 5 days per week. Subjects also performed progressively longer breathing trials daily per protocol. The weaning criterion was 72 consecutive hours without MV support. Subjects were blinded to group assignment, and were treated until weaned or 28 days.ResultsGroups were comparable on demographic and clinical variables at baseline. The IMST and SHAM groups respectively received 41.9 ± 25.5 vs. 47.3 ± 33.0 days of MV support prior to starting intervention, P = 0.36. The IMST and SHAM groups participated in 9.7 ± 4.0 and 11.0 ± 4.8 training sessions, respectively, P = 0.09. The SHAM groups pre to post-training maximal inspiratory pressure (MIP) change was not significant (-43.5 ± 17.8 vs. -45.1 ± 19.5 cm H2O, P = 0.39), while the IMST groups MIP increased (-44.4 ± 18.4 vs. -54.1 ± 17.8 cm H2O, P < 0.0001). There were no adverse events observed during IMST or SHAM treatments. Twenty-five of 35 IMST subjects weaned (71%, 95% confidence interval (CI) = 55% to 84%), while 16 of 34 (47%, 95% CI = 31% to 63%) SHAM subjects weaned, P = .039. The number of patients needed to be treated for effect was 4 (95% CI = 2 to 80).ConclusionsAn IMST program can lead to increased MIP and improved weaning outcome in FTW patients compared to SHAM treatment.Trial RegistrationClinicalTrials.gov: NCT00419458

Pulmonary delivery of liposomes

Abstract An overview of current data on pulmonary delivery of liposomes is provided, entailing fate of aerosols in the respiratory tract, physicochemical characterization of liposome aerosols, their therapeutic applications, pulmonary fate and kinetics, and pulmonary safety. Drugs that have been investigated for pulmonary delivery via liposomes include anticancer agents (ara-C), antimicrobials (enviroxime, amikacin, pentamidine), peptides (glutathione), enzymes (superoxide dismutase), antiasthmatic and antiallergic compounds (metaproterenol, salbutamol, cromolyn sodium, corticosteroids). Promising developments including pulmonary delivery of immunomodulators, antiviral agents and gene constructs (cystic fibrosis, α 1 -antitrypsin gene) are also discussed. Finally, pulmonary deposition and kinetics of drugs delivered via liposome aerosols, and targeting strategies to deliver drugs selectively to infected or impaired phagocytic (alveolar macrophages) and nonphagocytic (epithelial) cells in the lung are outlined. Based on the data on therapeutic efficacy and pulmonary safety currently available, we conclude that liposome aerosols may play an important future role in the therapy of pulmonary diseases including intracellular infections, immunologie disorders, and gene defects.

Pharmacokinetic/Pharmacodynamic Aspects of Aerosol Therapy using Glucocorticoids as a Model

Glucocorticoids are predominantly prescribed in asthma therapy as aerosols to achieve high pulmonary effects with reduced systemic spill‐over and pronounced pulmonary selectivity. A variety of pharmacokinetic parameters are potentially important for determining pulmonary selectivity. The intent of this article, is to provide a practice‐relevant theoretical approach to put the importance of these parameters on pulmonary targeting using pharmacokinetic/pharmacodynamic modeling as a tool in perspective. The applied pulmonary pharmacokinetic/pharmacodynamic model revealed that, in addition to recognized parameters such as systemic clearance, oral bioavailability, and efficiency of pulmonary deposition, other factors, such as the pulmonary release (dissolution) rate and dose, are relevant. However, the volume of distribution (for effect parameters not undergoing a diurnal rhythm) and the receptor affinity of a given glucocorticoid are not important for achieving lung targeting. J Clin Pharmacol 1997;37:881–892.

Pulmonary Effects of Chronic Exposure to Liposome Aerosols in Mice

Administering liposome-encapsulated drugs by aerosols could be a feasible way of targeting drugs to the lung, specifically to pulmonary alveolar macrophages (AM). In the mouse model, we characterized uptake of carboxyfluorescein- (CF-) labeled liposomes by AM in vivo after acute inhalation of liposome aerosols, and the effects of chronic exposure to liposome aerosols on lung histology and AM function. Mice were placed in a nose-only exposure module and exposed to liposome or saline aerosols for 1 h per day, 5 days per week, for 4 weeks. Five mice of both the experimental and control groups were removed weekly and their lungs examined. Liposomes were made from hydrogenated soy phosphatidylcholine (HSPC) at 50 mg/mL. In vivo uptake of liposomes by AM was documented by fluorescence microscopy and flow cytometry of bronchoalveolar lavage (BAL). A consistent amount of 1-3 micrograms of lipid inhaled per dosing per mouse was estimated from fluorescence measurements. Addition of Triton X-100 to BAL caused a significant increase in fluorescence intensity, indicating that liposomes remained intact in the lung for a period of time. The chronic inhalation study showed no histologic changes of the lung or untoward effects on the general health or survival of animals. AM phagocytic function, intracellular killing, and fatty acid composition were not affected. Transmission electron microscopy and morphometry (computerized image analysis) of AM likewise showed no alterations as a result of the treatment. It was concluded that AM uptake of liposomes delivered by aerosol was operant in vivo. This finding validates the concept of alveolar macrophage-directed delivery of liposome-encapsulated agents to the lung via inhalation. It was also concluded that chronic liposome aerosol inhalation in mice produced no untoward effects on survival, histopathology, and macrophage function. These data confirm and extend prior findings regarding the functional and morphologic interactions of liposomes with AM in vitro (Gonzalez-Rothi et al., Exp. Lung Res. 17:687-705, 1991).

Liposomes and pulmonary alveolar macrophages : functional and morphologic interactions

In vitro toxicity of liposomes and their functional and morphologic interactions with rat pulmonary alveolar macrophage (AMs) were investigated using viability (trypan blue exclusion), phagocytic and killing activity (uptake and digestion of live S. cerevisiae), surface adherence, respiratory burst (nitro-blue tetrazolium reduction), and morphometry (computerized image analysis) as indicators. Liposome stability in physiologic solutions and uptake of liposome-encapsulated carboxyfluorescein (CF) by AMs was assessed by fluorescence spectroscopy and microscopy. Liposomes made from saturated phospholipids and cholesterol were stable, whereas liposomes consisting of unsaturated phospholipids without cholesterol lost 30% to 40% of their content over 24 h. However, CF uptake was highest with unsaturated phospholipid preparations, whereas uptake of the three other formulations was comparable. Although liposome exposure did not affect macrophage viability, a reduction in the number of phagocytizing macrophages to 73% of control was noted after 24-h incubation with the highest lipid concentration tested (10 mumol/ml). Phagocytic killing was similar under all circumstances observed. The fraction of intracellularly killed yeast ranged from 32% to 42% for both control and experimental samples. An increase in cell surface area from 166.1 +/- 39.9 microns 2 on day O (n = 709) to 196.3 +/- 57.6 microns 2 on day 1 (n = 516) and 211.2 +/- 48.0 microns 2 on day 4 (n = 834) was observed after liposome treatment. The corresponding average cell areas of control samples did not change during the observation period. There was no net cell loss of adherence from monolayers as determined by protein assay. The respiratory burst, indicating generation of intracellular superoxide, was also similar--84% to 92% of experimental and control cells under all conditions showed a strong nitro-blue tetrazolium reduction. In summary, in vitro exposure of AMs to large concentrations of liposomes, although producing an increase in macrophage size, was not associated with aberrant macrophage morphologic features, function, or toxicity for the parameters examined.

Pulmonary targeting of liposomal triamcinolone acetonide phosphate.

AbstractPurpose. To explore the use of triamcinolone acetonide phosphate liposomes as a pulmonary targeted drug delivery system. Methods. Triamcinolone acetonide phosphate liposomes composed of 1,2-distearoyl phosphatidylcholine and 1,2-distearoyl phosphatidyl glycerol and triamcinolone acetonide 21-phosphate dipotassium salt were prepared by dispersion and extruded through polycarbonate membranes. Encapsulation efficiency and in vitro stability at 37°C were assessed after size exclusion chromatography. TAP liposomes (TAP-lip) or TAP in solution (TAP-sol) were delivered to rats either by intratracheal instillation (IT) or intravenous (IV) administration. Pulmonary targeting was assessed by simultaneous monitoring of glucocorticoid receptor occupancy over time in lung (local organ) and liver (systemic organ) using an ex vivo receptor binding assay as a pharmacodynamic measure of glucocorticoid action. Results.In vitro studies in different fluids over 24 hours, showed that more than 75% of the TAP remained encapsulated in liposomes. Cumulative pulmonary effects after IT administration of TAP-lip were 1.6 times higher than liver receptor occupancy. In contrast, there was no difference in the pulmonary and hepatic receptor occupancy time profiles when TAP was administered intratracheally as a solution. No preferential lung targeting was observed when TAP-lip was administered IV. As indicated by the mean effect times, lung receptor occupancy was sustained only when TAP-lip was administered IT. Conclusions. Intratracheal administration of TAP-lip provided sustained receptor occupancy, and increased pulmonary targeting which was superior to IT administration of TAP-sol or IV administration of TAP-lip. The use of liposomes may represent a valuable approach to optimize sustained delivery of glucocorticoids to the lungs via topical administration.

Effect of Dose and Release Rate on Pulmonary Targeting of Liposomal Triamcinolone Acetonide Phosphate

AbstractPurpose. To demonstrate the importance of dose and drug release rate for pulmonary targeting of inhaled glucocorticoids using an animal model of intrapulmonary drug deposition. Methods. Liposomes composed of 1,2-distearoyl phosphatidylcholine (DSPC), 1,2-distearoyl phosphatidylglycerol (DSPG) and triamcinolone acetonide phosphate (TAP) or liposomes containing triamcinolone acetonide (TA) were prepared by a mechanical dispersion method followed by extrusion through polycarbonate membranes. Encapsulation efficiency was assessed after size exclusion gel chromatography by reverse phase HPLC. The effect of liposome size (200 nm and 800 nm) on the release kinetics of water-soluble encapsulated material was determined in vitro at 37°C using 6-carboxyfluorescein as a marker and Triton X-100 (0.03%) as a leakage inducer. To investigate the relationship between drug release and pulmonary targeting, 100 μg/kg of TAP in 800 nm liposomes was delivered to male rats by intratracheal instillation (IT) and the results compared to data for 100 μg/kg TA liposomes (recently shown to exhibit a rapid drug release under sink conditions) and to previous studies reported for an equal dose of TAP in solution and TAP in 200 nm (1). Pulmonary targeting was assessed by simultaneously monitoring glucocorticoid receptor occupancy over time in lung and liver using an ex vivo receptor binding assay as a pharmacodynamic measure of glucocorticoid action. To assess the effect of dose on pulmonary targeting experiments were performed using 2.5, 7.5, 25, 100, and 450 μg/kg of TAP in 800 nm liposomes. Results. The in vitro efflux of 6-carboxyfluorescein from (DSPC:DSPG) liposomes after exposure to Triton-X was biexponential. The terminal half-lives of 3.7 h and 9.0 h for the 200 nm and 800 nm liposomes, respectively, demonstrated that larger liposomes promote slower release of encapsulated water-soluble solute while previous results already indicated that encapsulation of lipophilic TA does not result in sustained release. Pulmonary targeting, defined as the difference between cumulative lung and liver receptor occupancies was most pronounced for the 800 nm liposomes (370%*h), followed by the 200 nm preparation (150%*h). No targeting was observed for TAP in solution (30%*h) or the rapid releasing TA liposome preparation. Correspondingly, the mean pulmonary effect time (MET) increased from 2.4−3.0 hr for TA liposomes or TAP in solution to 5.7 h and >6.2 h for TAP in 200 nm and in 800 nm liposomes, respectively. Escalating doses of TAP encapsulated in 800 nm liposomes revealed a distinct bell shaped relationship between the TAP dose and pulmonary targeting with a maximum occurring at 100 μg/kg (370%*h). Conclusions. The in vivo data presented here confirm that pulmonary residence time and dose affect the extent of lung targeting of glucocorticoids delivered via the lung.

Amikacin liposomes: characterization, aerosolization, and in vitro activity against Mycobacterium avium-intracellulare in alveolar macrophages

Abstract A feasible way to treat pulmonary Myobacterium avium-intracellulare (MAI) infections is inhalation of liposome-encapsulated antimycobacterial agents aimed at infected alveolar macrophages (AM). To this end, amikacin-containing liposomes consisting of soy phosphatidylcholine (SPC), hydrogenated SPC (HSPC) and phosphatidylglycerol (PG) or cholesterol (CH) were prepared by extrusion and characterized with respect to drug content, encapsulation efficiency, drug retention in lung lavage fluid, stability during aerosolization, and in vitro efficacy against MAI in murine AM. Unencapsulated amikacin was separated by dialysis and ion-exchanged (Amberlite IRC50) adsorption which was found to be fast, complete and less cumbersome than dialysis. Drug content increased linearly with drug concentration for a fixed lipid concentration from 1 to 12% for SPC, and from 5 to 21% for SPC/PG (7:3 molar ratio) liposomes, while the amikacin content remained constant at 0.5–1% (SPC) and 1.5–2% (SPC/PG) over a lipid concentration range of 20–160 mg/ml for a fixed amikacin concentration. With increasing lipid concentration (10–160 mg/ml), the encapsulation efficiency increased linearly for SPC liposomes (2–20%), and in a saturable fashion for SPC/PG liposomes (1–35%). Aerosolization (Collison nebulizer) over 80 min resulted in loss of content of approx. 20% (SPC and HSPC) and 30–40% (SPC/PG and SPC/CH), respectively. Incubation with fresh lung lavage fluid at 37°C resulted in poor retention of amikacin in SPC/PG liposomes, whereas SPC and SPC/CH liposomes essentially retained the drug over 24 h. A dose of 20 μg/ml amikacin when encapsulated within SPC/PG liposomes was approx. 100-times efficacious against intracellular MAI in the infected alveolar macrophage model in vitro, than an equivalent concentration of free amikacin, indicating that uptake of drug-carrying liposomes by infected macrophages is operative.

Pulmonary delivery of amikacin liposomes and acute liposome toxicity in the sheep

Although liposome-encapsulated antibiotics designed for intrapulmonary delivery by instillation or aerosolization have been proposed, little is known about the pharmacokinetic profile and toxicity of liposomal drug formulations when delivered to the lung. A technique for large-scale preparation of sterile amikacin liposomes including preparation of a lyophilized amikacin/phospholipid coprecipitate and a highly efficient hollow-fiber dialysis method for rapid removal of unencapsulated drug is described. Doses of 5 and 15 mg/kg amikacin solution or 15 and 45 mg/kg amikacin-containing liposomes consisting of soy phosphatidylcholine/ phosphatidylglycerol (SPC/PG 7:3, molar ratio) or SPC/PG with cholesterol (SPC/PG/CH 4:3:3) were administered intratracheally into intubated, awake sheep. For the 15 mg/kg amikacin solution, the terminal half-life time (t12) was 117 min with maximum plasma levels (cpmax) of 8.3 μg/ml after 2 h and a bioavailability of 38%. The t12 for both doses of amikacin-SPC/PG liposomes was greater than 3 h. Bioavailability varied from 35 to 58%, with a cpmax of 5.5 μg/ml (15 mg/kg) and 23.6 μg/ml (45 mg/kg) after 1.5 h. The t12 of amikacin-SPC/PG/CH liposomes was greater than 10 h with a cpmax of 3.3 μg/ml after 3 h and a bioavailability of 46%. The dosage form was found to be the overall rate-limiting factor for amikacin pharmacokinetics. For assessment of pulmonary function and blood gases, awake sheep inhaled plain liposomes consisting of 15 and 150 mg/ml SPC or hydrogenated SPC (HSPC) for 30 min via a Collision nebulizer. Dynamic compliance (Cdyn), lung resistance (RL), paO2 and paCO2 were analyzed for 6 h post-inhalation (acute effects 0–2 h; delayed effects 2–6 h). All parameters remained within physiologically normal ranges over the entire observation period. It was concluded that liposomes delivered by the pulmonary route act as local sustained release reservoir, and are safe and nonirritating to the lung.

Midazolam-associated alterations in cardiorespiratory function during colonoscopy.

Twenty patients undergoing clinically indicated elective colonoscopy were prospectively monitored noninvasively for alterations in cardiorespiratory function. Most of the patients were elderly and many had either cardiac or pulmonary disease. All subjects were premedicated with intramuscular meperidine and continuously monitored with ECG, blood pressure, earlobe pulse oximetry, nasal air flow by thermistor probe, and impedance pneumography. Any use of additional analgesic or sedative was determined by the endoscopist, who was blinded to the physiologic tracings, and dosages of medications given were titrated to each patients tolerance of the procedures as assessed by the endoscopist. Seventeen patients (85%) required additional sedation with the benzodiazepine, midazolam. These patients exhibited frequent episodes of hypotension (reductions in mean arterial blood pressure of 23 +/- 12 mm Hg from baseline, means +/- SD) and respiratory depression (as noted by the greater number of apneas and arterial oxygen desaturation as low as 7.1 +/- 2% from baseline, means +/- SD). In addition, elderly patients and patients with an underlying history of cardiac or pulmonary disease had a greater incidence of potentially untoward cardiorespiratory events.