Anaphylaxis Induced by Intravenous Tacrolimus Administration During Kidney Transplant Surgery: A Case Report.

A 35-year-old male patient with end-stage renal disease due to vesicoureteral reflux preemptively received a renal graft from his father. The patient had a history of allergy to contrast-enhancing media. He received oral tacrolimus (TAC) and mycophenolate mofetil without any problems for 2 days before kidney transplantation. During the induction period of the surgery, his systolic blood pressure (sBP) decreased to 60 mmHg approximately 1 hour after initiating intravenous tacrolimus (TAC-IV) and intravenous piperacillin (PIPC), and the anesthesiologist suspected drug-induced anaphylaxis and stopped administration of the medications. Because TAC had been administered preoperatively without any adverse events, PIPC was suspected as the causative agent of the anaphylaxis. After the patient's hemodynamics returned to baseline, TAC-IV was restarted. However, his sBP rapidly decreased to 40 mmHg and the patient developed wheezing. He was diagnosed with drug-induced anaphylaxis due to castor oil derivatives in the TAC-IV formulation. The patient's sBP was restored with the administration of some vasopressors, and kidney transplantation was then performed without difficulty. Two days after kidney transplantation, oral TAC was administered without anaphylaxis. Clinicians should consider that not only the drug itself but also its additives or metabolites could induce anaphylaxis.

Preparation and Characterization of Tacrolimus-Loaded SLNs in situ Gel for Ocular Drug Delivery for the Treatment of Immune Conjunctivitis.

BACKGROUND: The aim of this study is to develop a novel in situ gel of tacrolimus-loaded SLNs (solid lipid nanoparticles) for ocular drug delivery. METHODS: The optimal formulation was characterized by surface morphology, particle size, zeta potential, entrapment efficiency, drug loading and in vitro release behavior. In vivo studies were also conducted to evaluate the pharmacokinetic and pharmacodynamic results. RESULTS: In this study, TAC-SLNs ISG were prepared using homogenization followed by probe sonication method. The average particle size of TAC-SLNs ISG was observed to be 122.3±4.3 nm. Compared with TAC-SLNs, in situ gel did not increase particle size, and there was no significant difference between them. The results of viscosity measurement showed that TAC SLNs-ISG were typical of pseudo plastic systems and showed a marked increase in viscosity as temperature increased and ultimately formed a rigid gel (32°C). In vitro and in vivo studies illustrated the sustained release model of the drug from TAC-SLNs ISG. Animal model showed that TAC-SLNs ISG had good pharmacodynamics when compared with eye drops and SLNs. CONCLUSION: Our results demonstrated that TAC SLNs-ISG had the potential for being an ideal ocular drug delivery system.

Design of novel tacrolimus formulations with chemically synthesized oils for oral lymphatic delivery.

High consumption of oil formulations has been reported to reduce the blood exposure of drugs like tacrolimus. Consumption of oil formulations has also been shown to inhibit T-cell production of interleukin-2 (IL-2) compared to solid dispersion formulations (SDFs). However, a large amount of oil causes gastrointestinal side effects such as diarrhea and low compliance. Here, we investigated the feasibility of reducing the amount of oil and substitution of chemically synthetized oils for natural oils in these formulations. Reducing the amount of sunflower oil increased blood tacrolimus exposure despite sufficient suppression of IL-2 production. While medium-chain triglyceride (MCT) increased tacrolimus blood exposure, addition of 10% glyceryl monostearate (GMS) to MCT significantly decreased drug blood exposure without requiring a large amount of oil (p < .05). Effects of the contents of GMS in the MCT/GMS formulations, and fatty acid composition in GMS on drug blood exposure were also investigated. The results indicated that both the amount and type of oil were important for maintaining a good balance between a reduction in blood exposure and sufficient IL-2 suppression. The ratio of drug concentration in lymphocytes to that in whole blood after dosing with an oil formulation was significantly higher than that after administration of the SDF (p < .01). These results indicate the feasibility of developing oral oil tacrolimus formulations to reduce systemic side effects and maintain high efficacy for practical use in patients.

Tacrolimus-loaded lecithin-based nanostructured lipid carrier and nanoemulsion with propylene glycol monocaprylate as a liquid lipid: Formulation characterization and assessment of dermal delivery compared to referent ointment.

Nanostructured lipid carriers (NLC) and nanoemulsions (NE) are colloid carriers which could improve dermal delivery of tacrolimus. The aims of this study were to evaluate effects of different formulation and process parameters on physicochemical characteristics and stability of lecithin-based NLC with glyceryl palmitostearate as solid and propylene glycol monocaprylate as liquid lipid and to compare the influence of different inner structure of tacrolimus-loaded NLC and corresponding NE on physicochemical characteristics, stability, entrapment efficiency, in vitro drug release and overall skin performance. Solid/liquid lipid ratio, total amount of lipids, homogenization pressure and cooling after the preparation were identified as critical variables in NLC development. Moreover, tacrolimus-loaded NLC emerged as more stabile carrier than NE. Differential stripping performed on porcine ear skin revealed significantly higher tacrolimus amount in stratum corneum from nanocarriers compared to referent ointment (Protopic®). Similarly the highest amount of tacrolimus in hair follicles was obtained using NLC (268.54 ±â€¯92.38 ng/cm2), followed by NE (128.17 ±â€¯48.87 ng/cm2) and Protopic® (77.61 ±â€¯43.25 ng/cm2). Contrary, the highest permeation rate through full-thickness porcine ear skin was observed for Protopic®, implying that the selection of experimental setup is critical for reliable skin performance assessment. Overall, developed NLC could be suggested as promising carrier in a form of lotion for tacrolimus dermal delivery.

Pharmacokinetics of topically applied tacrolimus dissolved in Marinosolv, a novel aqueous eye drop formulation.

Corticosteroids and macrolide immunomodulators such as tacrolimus are effective drugs for the topical treatment of inflammatory eye diseases like allergic conjunctivitis or dry eye. However, tacrolimus is practically insoluble in aqueous solutions and is therefore currently formulated as dispersion. This leads to low bioavailability. Here, we present a novel pharmacologically acceptable, aqueous formulation of tacrolimus based on the "Marinosolv formulation platform". Marinosolv allows the solubilization and thereby improvement of the bioavailability of many otherwise practically insoluble drugs, since dissolved drugs permeate faster into tissues, including ocular tissues. To visualize the benefits of Marinosolv in ophthalmic formulations, we investigated the permeation of a fluorescently labeled estradiol dissolved in Marinosolv compared to a formulation containing the compound as dispersion. Permeation was studied ex-vivo and in-vivo in porcine eyes. Further, we evaluated the improved permeation of topically applied tacrolimus dissolved in Marinosolv compared to a commercially available topically applied tacrolimus dispersion. The Marinosolv formulation was also compared to oral tacrolimus treatment, the standard application route for this drug in case of severe posterior uveitis. Finally, the ocular tissue levels of tacrolimus in all groups were determined using HPLC/MS. We demonstrated that tacrolimus dissolved in Marinosolv reached significantly higher levels in ocular tissues compared to the marketed topical product or after oral application and thus may be a suitable novel option for the treatment of several eye diseases, such as allergic conjunctivitis or uveitis. Thus, Marinosolv may be considered as a new vehicle for tacrolimus eye drops.

Crystallization from Supersaturated Solutions: Role of Lecithin and Composite Simulated Intestinal Fluid.

PURPOSE: The overall purpose of this study was to understand the impact of different biorelevant media types on solubility and crystallization from supersaturated solutions of model compounds (atazanavir, ritonavir, tacrolimus and cilnidipine). The first aim was to understand the influence of the lecithin content in FaSSIF. As the human intestinal fluids (HIFs) contain a variety of bile salts in addition to sodium taurocholate (STC), the second aim was to understand the role of these bile salts (in the presence of lecithin) on solubility and crystallization from supersaturated solutions, METHODS: To study the impact of lecithin, media with 3 mM STC concentration but varying lecithin concentration were prepared. To test the impact of different bile salts, a new biorelevant medium (Composite-SIF) with a composition simulating that found in the fasted HIF was prepared. The crystalline and amorphous solubility was determined in these media. Diffusive flux measurements were performed to determine the true supersaturation ratio at the amorphous solubility of the compounds in various media. Nucleation induction times from supersaturated solutions were measured at an initial concentration equal to the amorphous solubility (equivalent supersaturation) of the compound in the given medium. RESULTS: It was observed that, with an increase in lecithin content at constant STC concentration (3 mM), the amorphous solubility of atazanavir increased and crystallization was accelerated. However, the crystalline solubility remained fairly constant. Solubility values were higher in FaSSIF compared to Composite-SIF. Longer nucleation induction times were observed for atazanavir, ritonavir and tacrolimus in Composite-SIF compared to FaSSIF at equivalent supersaturation ratios. CONCLUSIONS: This study shows that variations in the composition of SIF can lead to differences in the solubility and crystallization tendency of drug molecules, both of which are critical when evaluating supersaturating systems.

Modeling Analysis of Potential Target of Dolastatin 16 by Computational Virtual Screening.

Dolastatin 16 is a cyclic depsipeptide isolated from the marine invertebrates and cyanobacterium Lyngbya majuscula, however, its bioactivity has been a historical question. In this study, peptidyl-prolyl cis-trans isomerase FKBP1A (FKBP12) was predicted as a potential target of dolastatin 16 via PharmMapper as well as verified using chemical-protein interactome (CPI) and molecular docking. FKBP1A has been previously identified as a target for the natural polyketide FK506 (tacrolimus), an immune suppressor inhibiting the rejection of organ transplantation in clinical use. The comparison study via the reverse pharmacophore screening and molecular docking of dolastatin 16 and FK506 indicated the good consistency of analysis with the computational approach. As the results, the lowest binding energy of dolastatin 16-FKBP1A complex was -7.4 kcal/mol and FK506-FKBP1A complex was -8.7 kcal/mol. The ligand dolastatin 16 formed three hydrogen bonds vs. four of FK506, as well as seven hydrophobic interactions vs. six of FK506 within the active site residues. These functional residues are highly repetitive and consistent with previously reported active site of model of FK506-FKBP1A complex, and the pharmacophore model was shown feasibly matching with the molecular feature of dolastatin 16.

The Anti-Inflammatory Effects of Oral-Formulated Tacrolimus in Mice with Experimental Autoimmune Encephalomyelitis.

Multiple sclerosis (MS) is a T-lymphocyte-mediated autoimmune disease that is characterized by inflammation in the central nervous system (CNS). Although many disease-modifying therapies (DMTs) are presumed effective in patients with MS, studies on the efficacy and safety of DMTs for preventing MS relapse are limited. Therefore, we tested the immunosuppressive anti-inflammatory effects of oral-formulated tacrolimus (FK506) on MS in a mouse model of experimental autoimmune encephalomyelitis (EAE). The mice were randomly divided into 3 experimental groups: an untreated EAE group, a low-dose tacrolimus-treated EAE group, and a high-dose tacrolimus-treated EAE group. After autoimmunization of the EAE mice with myelin oligodendrocyte glycoprotein, symptom severity scores, immunohistochemistry of the myelination of the spinal cord, and western blotting were used to evaluate the EAE mice. After the autoimmunization, the symptom scores of each EAE group significantly differed at times. The group treated with the larger tacrolimus dose had the lowest symptom scores. The tacrolimus-treated EAE groups exhibited less demyelination and inflammation and weak immunoreactivity for all of the immunization biomarkers. Our results revealed that oral-formulated tacrolimus inhibited the autoimmunization in MS pathogenesis by inactivating inflammatory cells.

Oral tacrolimus oil formulations for enhanced lymphatic delivery and efficient inhibition of T-cell's interleukin-2 production.

Oral oil formulations have been reported to deliver drugs into the lymph. Lymphatic delivery of immunomodulatory drugs can more efficiently expose the drugs to T-cells in lymph, consequently induce higher efficacy and lower side effects. In this study, effects of tacrolimus oral oil formulations on drug blood exposure, and on inhibition of T-cell's interleukin-2 (IL-2) production were investigated in rats. Oil formulations (sunflower oil, cacao butter, medium chain triglyceride, and palm oil) dissolving tacrolimus showed lower drug blood concentration than a solid dispersion formulation (SDF). The sunflower oil, and cacao butter formulations suppressed drug blood exposure to 50% of the SDF, and inhibited T-cell's IL-2 production similar to the SDF. In vitro digestion tests indicated that slower digestion of the oils might reduce amount and rate of tacrolimus blood absorption. The cacao butter formulations showed 3.0 times more rapid tacrolimus absorption to lymphatic fluid than the SDF. Ratio of the rate constants of absorption into lymph to that into blood was higher in oil formulations (15 times in cacao butter, 15 times sunflower oil, and 3.5 times palm oil) than in the SDF. These results indicated that the oral oil formulations might be suitable for reduced tacrolimus blood concentration for low systemic side effects, and keep high lymph concentration for high efficacy in organ transplantation patients.

Solid state compatibility study and characterization of a novel degradation product of tacrolimus in formulation.

Tacrolimus is macrolide drug that is widely used as a potent immunosuppressant. In the present work compatibility testing was conducted on physical mixtures of tacrolimus with excipients and on compatibility mixtures prepared by the simulation of manufacturing process used for the final drug product preparation. Increase in one major degradation product was detected in the presence of magnesium stearate based upon UHPLC analysis. The degradation product was isolated by preparative HPLC and its structure was elucidated by NMR and MS studies. Mechanism of the formation of this degradation product is proposed based on complementary degradation studies in a solution and structural elucidation data. The structure was proven to be alpha-hydroxy acid which is formed from the parent tacrolimus molecule through a benzilic acid type rearrangement reaction in the presence of divalent metallic cations. Degradation is facilitated at higher pH values.

Proniosome-derived niosomes for tacrolimus topical ocular delivery: in vitro cornea permeation, ocular irritation, and in vivo anti-allograft rejection.

The objective of this study was to develop proniosome-derived niosomes for topical ophthalmic delivery of Tacrolimus (FK506). The FK506 loaded proniosomes containing poloxamer 188 and lecithin as surfactants, cholesterol as a stabilizer, and minimal amount of ethanol and trace water reconstituted to niosomes prior to use. The stability of FK506 loaded proniosomes was assessed, and the morphology, size, zeta potential, surface tension, and entrapment efficiency of the derived niosomes were characterized, indicating they were feasible for instillation in the eyes. The in vitro permeation of FK506 through the freshly excised rabbit cornea, the cumulative permeation amount of FK506 from niosomes, and the drug retention in the cornea all exhibited significant increase as compared to 0.1% FK506 commercial ointments. The in vivo ocular irritation test of 0.1% FK506 loaded niosomes instilled 4 times per day in rat eyes for 21 consecutive days showed no irritation and good biocompatibility with cornea. The in vivo anti-allograft rejection assessment was performed in a Sprague-Dawley (SD) rat corneal xenotransplantation model. The results showed treatment with 0.1% FK506 loaded niosomes delayed the occurrence of corneal allograft rejection and significantly prolonged the median survival time of corneal allografts to13.86±0.80days as compared with those treated with 1% Cyclosporine (CsA) eye drops, drug-free niosomes, or untreated. In conclusion, the proniosome-derived niosomes may be a promising vehicle for effective ocular drug delivery of FK506.

Calcineurin inhibitors: 40 years later, can't live without ...

Calcineurin inhibitors (CNIs) revolutionized the field of organ transplantation and remain the standard of care 40 years after the discovery of cyclosporine. The early impressive results of cyclosporine in kidney transplant recipients led to its subsequent use in other organ transplant recipients and for treatment of a variety of autoimmune diseases as well. In this review, we examine the discovery of CNIs, their mechanism of action, preclinical and clinical studies with CNIs, and the usage of CNIs in nontransplant recipients. We review the mechanisms of renal toxicity associated with CNIs and the recent efforts to avoid or reduce usage of these drugs. Although minimization strategies are possible, safe, and of potential long-term benefit, complete avoidance of CNIs has proven to be more challenging than initially thought.

Rapid identification of antifungal compounds against Exserohilum rostratum using high throughput drug repurposing screens.

A recent large outbreak of fungal infections by Exserohilum rostratum from contaminated compounding solutions has highlighted the need to rapidly screen available pharmaceuticals that could be useful in therapy. The present study utilized two newly-developed high throughput assays to screen approved drugs and pharmaceutically active compounds for identification of potential antifungal agents. Several known drugs were found that have potent effects against E. rostratum including the triazole antifungal posaconazole. Posaconazole is likely to be effective against infections involving septic joints and may provide an alternative for refractory central nervous system infections. The anti-E. rostratum activities of several other drugs including bithionol (an anti-parasitic drug), tacrolimus (an immunosuppressive agent) and floxuridine (an antimetabolite) were also identified from the drug repurposing screens. In addition, activities of other potential antifungal agents against E. rostratum were excluded, which may avoid unnecessary therapeutic trials and reveals the limited therapeutic alternatives for this outbreak. In summary, this study has demonstrated that drug repurposing screens can be quickly conducted within a useful time-frame. This would allow clinical implementation of identified alternative therapeutics and should be considered as part of the initial public health response to new outbreaks or rapidly-emerging microbial pathogens.

Cotton-made cellulose support for anti-allergic pajamas.

The cotton used to produce an interlock knitted fabric is alkaline boiled, bleached and after drying, it is grafted with monochlorotriazinyl-beta-cyclodextrin (MCT-ß-CD) as a support of an inclusion compound (IC) with natural anti-allergic active principles, in order to improve the curative properties and the comfort. Are used: extract of Viola tricolor Herb (VtH), solution of propolis (P) and of menthol (M), as well as the pharmacologic products: advantan (AD), hydrocortisone (HYD) and pimechrolimus (PI). The dimensions of the active compound molecules were established with software. The textile material grafted with MCT-ß-CD and with active principles absorbed in the cyclodextrin cavity is investigated by EDX. The anti-microbial activity of VtH, P and M was tested. Tactile determinations of softness were performed with human appraisers. By assembling the anti-allergic knitted fabric with untreated fabric, therapeutic pajamas were obtained. The manner to process and manufacture the pajamas for patients with contact and atopic (DA) dermatitis (DC) is presented.

[Galenic and analytic development of tacrolimus 0.06% eye drops]. / Développement galénique et analytique d'un collyre à base de tacrolimus 0,06 %

PURPOSE: The administration of topical tacrolimus (FK506) eye drops or ointment is effective in treating certain immunologic corneal diseases and in the prevention of rejection of high-risk corneal grafts. The purpose of this study is to determine the optimal formulation of tacrolimus 0.06% eye drops. A procedure for preparation is presented and discussed. METHODS: Tacrolimus monohydrate powder and virgin castor oil are used in this new formulation. The manufacturing process guarantees consistency of product sterility. Measurement by high-performance liquid chromatography allows precise control of the concentration of tacrolimus. RESULTS: The manufacture and packaging of tacrolimus 0.06% eye drops involve numerous controls allowing for guaranteed sterility and stability. The drops remained sterile and stabile for 28 days after opening regardless of storage conditions and can be stored for 3 months after manufacture. Tolerability studies are currently being performed.

Development and evaluation of colloidal modified nanolipid carrier: application to topical delivery of tacrolimus, Part II--in vivo assessment, drug targeting, efficacy, and safety in treatment for atopic dermatitis.

In atopic dermatitis (AD), topical anti-inflammatory therapy with skin barrier restoration to prevent repeated inflammatory episodes leads to long-term therapeutic success. Tacrolimus, although effective against AD, is a challenging molecule due to low solubility, low-penetration, poor-bioavailability, and toxicity. Part I of this paper, reported novel modified nanolipid carrier system for topical delivery of tacrolimus (T-MNLC), offering great opportunity to load low-solubility drug with improved entrapment efficiency, enhanced stability and improved skin deposition. Present investigation focused on restoration of skin barrier, site-specific delivery, therapeutic effectiveness, and safety of novel T-MNLC. T-MNLC greatly enhanced occlusive properties, skin hydration potential and reduced transepidermal water loss. This might help to reduce the number of flares and better control the disease. Cutaneous uptake and drug deposition in albino rats by HPLC and confocal laser scanning microscopy revealed prominently elevated drug levels in all skin strata with T-MNLC as compared to reference. T-MNLC demonstrated efficient suppression of inflammatory responses in BALB/c mice model of AD. Safety assessment by acute and repeated-dose dermal toxicity demonstrated mild keratosis and collagenous mass infiltration at the treatment area with repeated application of reference. Interestingly, T-MNLC showed no evident toxicity exhibiting safe drug delivery. Thus, novel T-MNLC would be a safe, effective, and esthetically appealing alternative to conventional vehicles for treatment for AD.

Rice germ oil as multifunctional excipient in preparation of self-microemulsifying drug delivery system (SMEDDS) of tacrolimus.

Surmounting the constraints of limited solubilization efficiency and prime requisite of antioxidant for conventional lipid formulations, the research work explores an edge over formulation utilizing potential applicability of rice germ oil (RGO) as a multifunctional excipient. Self-microemulsifying drug delivery system (SMEDDS) of tacrolimus (TAC) was formulated with RGO, an indigenous source of gamma-oryzanol. Being the same biological source, RGO and rice bran oil (RBO) were compared and it was found that RGO have more solubilization potential for TAC (2.2-fold) as well as higher antioxidant activity (8.06-fold) than the RBO. TAC-SMEDDS was prepared using RGO/Capmul PG8 (2:3) as an oil phase, Cremophore EL as a surfactant, and Transcutol P as a cosurfactant. The approximate particle size of TAC-SMEDDS was found to be 38 nm by dynamic light scattering and 12 nm by small angle neutron scattering. The in vitro dissolution studies showed complete and rapid drug release in 30 min compared to a plain drug (<5%) and marketed capsule (<50%). AUC and C(max) were found to be 45.05 ± 15.64 ng h/ml and 3.91 ± 1.2 ng/ml for TAC-SMEDDS, 12.59 ± 5.54 ng h/ml and 0.48 ± 0.12 ng/ml for plain TAC, and 30.23 ± 10.34 ng h/ml and 2.31 ± 0.68 ng/ml for marketed formulation, respectively. The improved pharmacokinetic profile of TAC-SMEDDS is correlating to the dissolution results. Thus, gamma-oryzanol-enriched RGO acts as a potential multifunctional excipient for lipid formulations.

Effects of water-soluble tacrolimus-PEG conjugate on insulin-dependent diabetes mellitus and systemic lupus erythematosus.

The effects of a water-soluble tacrolimus-PEG conjugate (KI-102) on insulin-dependent diabetes mellitus and systemic lupus erythematosus were investigated. KI-102 was stable at pH 4.0-4.5 and 4°C. The area under the concentration-time curve, the time of maximum concentration, and the maximum concentration were 43.4 ng·h/mL, 0.85 h, and 8.1 ng/mL, respectively, similar to those of FK506. Mice that administered KI-102 at 4.32 mg/kg had the plasma glucose concentrations that decreased to 7.5 mmol/L after 170 days, similar to that of mice administered FK506 at 0.6 mg/kg. There were no incidences of diabetes when KI-102 was administered at 86.4 mg/kg after 24 weeks. The group that administered 43.2 mg/kg had decreases in the concentrations of ß-hydroxybutyrate (60%), triglyceride (24%), and cholesterol (30%). KI-102 administered at 180 mg/kg reduced serum anti-dsDNA antibody activity by 64% compared with a control. Urinary albumin concentration in the same group decreased 81% compared with the control. These results indicate that KI-102 may be practically applicable as prodrug of FK506.

Development and evaluation of colloidal modified nanolipid carrier: application to topical delivery of tacrolimus.

Low solubility of tacrolimus in carrier matrix and subsequent poor in vivo bioavailability was overcome by constructing modified nanolipid carrier (MNLC) as a novel approach. The aim of this study was to develop MNLC with enhanced drug solubility in carrier lipid matrix using lipophilic solubilizers for topical delivery. Comprehensive characterization of tacrolimus-loaded MNLC (T-MNLC) was carried out for particle size, morphology, and rheology. Lipid modification resulted in the formation of less perfect crystals offering space to accommodate the dissolved drug leading to high entrapment efficiency of 96.66%. Compatibility and mixing behavior of carrier constituents was evaluated using DSC, FT-IR, and (1)H NMR. T-MNLC displayed sufficient stability that could be attributed to possibility to reduce total lipid concentration in carrier. T-MNLC-enriched gels showed significantly higher in vitro drug release, skin permeation, and in vivo bioavailability with dermatopharmacokinetic approach in guinea pigs compared to commercial ointment, Protopic® as reference. Penetration-enhancing effect was confirmed using gamma scintigraphy in vivo in rats. Radioactivity remained localized in skin at the application site avoiding unnecessary biodisposition to other organs with prospective minimization of toxic effects. Skin irritation studies showed T-MNLC to be significantly less irritating than reference. Research work could be concluded as successful development of novel T-MNLC using lipophilic solubilizers to increase the encapsulation efficiency of colloidal lipid carriers with advantage of improved performance in terms of stability and skin localization.

Preclinical evaluation of tacrolimus colloidal dispersion for inhalation.

Substantial improvements in transplant therapy have been made in the past four decades resulting in the acceptance of organ transplantation as a viable treatment for late-stage disease and organ failure. More recently, lung transplantation has gained acceptance; however, high incidence of chronic rejection and opportunistic infections has limited success rates in comparison with other transplant procedures. To achieve more targeted therapy, pulmonary administration of nebulized tacrolimus (TAC) colloidal dispersion once daily for 28 consecutive days in Sprague Dawley (SD) rats has been investigated for safety and systemic elimination. A liquid dispersion of colloidal TAC and lactose (1:1 ratio by weight) was aerosolized using a vibrating mesh nebulizer and administered via a nose-only dosing chamber. Blood chemistry and histological comparisons to saline-dosed animals showed no clinically significant differences in liver and kidney function or lung tissue damage. Maximum blood and lung concentrations sampled 1h after the final dose showed TAC concentrations of 10.1 ± 1.4 ng/mL and 1758.7 ± 80.0 ng/g, respectively. Twenty-four hours after the final dose, systemic TAC concentrations measured 1.0 ± 0.5 ng/mL, which is well below clinically accepted trough concentrations (5-15 ng/mL) for maintenance therapy, and therefore, would not be expected to induce toxic side effects. The propensity for pulmonary retention seen when compared to single dose lung levels may be due to macrophage uptake and the lipophilic nature of TAC. Additionally, three month stability testing of TAC powder for reconstitution showed no changes in amorphous nature or drug potency when stored at ambient conditions. TAC colloidal dispersion proved to be non-toxic when administered by pulmonary inhalation to SD rats over 28 days while providing therapeutic concentrations locally. This delivery strategy may prove safe and effective for the prevention of lung allograft rejection in lung transplant recipients.