In-situ forming biodegradable implants for sustained Fluocinolone acetonide release to the posterior eye: In-vitro and in-vivo investigations in rabbits

Delivering medication to the posterior segment of the eye presents a significant challenge. Intravitreal injection has emerged as the preferred method for drug delivery to this area. However, current injectable non-biodegradable implants for fluocinolone acetonide (FA) require surgical removal after prolonged drug release, potentially affecting patient compliance. This study aimed to develop an in-situ forming biodegradable implant (ISFBI) optimal formulation containing PLGA504H and PLGA756S (50:50 w/w%) with the additive NMP solvent. The goal was to achieve slow and controlled release of FA over a two-month period with lower burst release, following a single intravitreal injection. Through morphology, rheology, stability and in-vitro release evaluations, the optimal formulation demonstrated low viscosity (0.12-1.25 Pa. s) and sustained release of FA at a rate of 0.36 µg/day from the third day up to two months. Furthermore, histopathology and in-vivo studies were conducted after intravitreal injection of the optimal formulation in rabbits' eye. Pharmacokinetic analysis demonstrated mean residence time (MRT) of 20.02 ± 0.6 days, half-life (t1/2) of 18.80 ± 0.4 days, and clearance (Cl) of 0.29 ± 0.03 ml/h for FA in the vitreous humor, indicating sustained and slow absorption of FA by the targeted retinal tissue from vitrea over the two-month period and eliminating through the anterior section of the eye, as revealed by its presence in the aqueous humor. Additionally, FA exhibited no detection in the blood and no evidence of systemic side effects or damage on the retinal layer and other organs. Based on these findings, it can be concluded that in-situ forming injectable biodegradable PLGA implants can show promise as a long-acting and controlled-release system for intraocular drug delivery.

INTRAVITREAL CORTICOSTEROIDS IN DIABETIC MACULAR EDEMA: PHARMACOKINETIC CONSIDERATIONS

PURPOSE

To review the relationship between kinetics, efficacy, and safety of several corticosteroid formulations for the treatment of diabetic macular edema.

METHODS

Reports of corticosteroid use for the treatment of diabetic macular edema were identified by a literature search, which focused on the pharmacokinetics, efficacy, and safety of these agents in preclinical animal models and clinical trials.

RESULTS

Available corticosteroids for diabetic macular edema treatment include intravitreal triamcinolone acetonide, dexamethasone, and fluocinolone acetonide. Because of differences in solubility and bioavailability, various delivery mechanisms are used. Bioerodible delivery systems achieve higher maximum concentrations than nonbioerodible formulations. There is a relationship between visual gains and drug persistence in the intravitreal compartment. Safety effects were more complex; level of intravitreal triamcinolone acetonide exposure is related to development of elevated intraocular pressure and cataract; this does not seem to be the case for dexamethasone, where two different doses showed similar mean intraocular pressure and incidence of cataract surgery. With fluocinolone acetonide, rates of intraocular pressure elevations requiring surgery seem to be dose related; rates of cataract extraction were similar regardless of dose.

CONCLUSION

Available corticosteroids for diabetic macular edema exhibit different pharmacokinetic profiles that impact efficacy and adverse events and should be taken into account when developing individualized treatment plans.

A reappraisal of the clinical efficacy of nebulized flunisolide in pediatric asthma: the Italian experience

Flunisolide (FLU) is a synthetic corticosteroid with potent topical anti-inflammatory activity. Its oral bioavailability is poor (6.7%). After gastrointestinal and lung absorption, the drug undergoes rapid and extensive first-pass metabolism by the liver to an inactive 6beta-hydroxylated metabolite. Plasma half-life is estimated to be 3.9 to 4.6 hours. FLU has a low volume of distribution at steady state and a short terminal half-life after inhalation (96 L and 1.6 hour, respectively). FLU, like budesonide, has a short pulmonary residence time and it is hypothesized that it may undergo esterification in the cell due to the presence of a free hydroxyl group at C21. Nebulization may offer important advantages over other inhalation methods. Nebulizers allow drug delivery in very young children through passive inhalation, depending less on patient coordination and cooperation. Comparative studies indicate that FLU is nebulized to a better advantage than beclomethasone dipropionate and budesonide. This is attributed to its elevated water solubility. The aim of this article is to outline the factors that influence drug nebulization and the pharmacokinetics-pharmacodynamics of FLU compared to other inhaled corticosteroids. In addition, we report a series of clinical data regarding the efficacy of nebulized FLU with focus on the Italian experience. Overall, the physicochemical characteristics and pharmacokinetic profile of FLU favor its use for nebulization. Clinical data indicate that nebulized FLU is effective in asthma treatment in infants and children. Side effects were not reported at the commonly used doses.

Long-term release of fluocinolone acetonide using biodegradable fumarate-based polymers

Intraocular drug delivery systems made from biodegradable polymers hold great potential to effectively treat chronic diseases of the posterior segment of the eye. This study is based on the hypothesis that crosslinked poly(propylene fumarate) (PPF)-based matrices are suitable long-term delivery devices for the sustained release of the anti-inflammatory drug fluocinolone acetonide (FA) due to their hydrophobicity and network density. FA-loaded rods of 10 mm length and 0.6 mm diameter were fabricated by photo-crosslinking PPF with N-vinyl pyrrolidone (NVP). The released amounts of FA and NVP were determined by HPLC analysis. The effects of drug loading and the ratio of PPF to NVP on the release kinetics were investigated using a 2(3-1) factorial design. Overall, FA release was sustained in vitro over almost 400 days by all tested formulations. Low burst release was followed by a dual modality release controlled by diffusion and bulk erosion with release rates up to 1.7 microg/day. The extent of the burst effect and the release kinetics were controlled by the drug loading and the matrix composition. Matrix water content and degradation were determined gravimetrically. Micro-computed tomography was used to image structural and dimensional changes of the devices. The results show that photo-crosslinked PPF-based matrices are promising long-term delivery devices for intraocular drug delivery.

Efficacy of Low-Release-Rate Fluocinolone Acetonide Intravitreal Implants to Treat Experimental Uveitis

OBJECTIVE

To determine the efficacy of 0.5-mg and 0.1-mg sustained-release fluocinolone acetonide intravitreal implants to inhibit ocular inflammation in a rabbit model of severe uveitis.

METHODS

The in vitro pharmacokinetic profile of both the 0.5-mg and 0.1-mg sustained-release fluocinolone intravitreal implants was determined during a 10-day period. A sustained-release fluocinolone acetonide intravitreal implant with a release rate of either 0.5 microg/d (n = 16) or 0.1 microg/d (n = 16) was implanted into the vitreous cavity of the right eye in albino rabbits after a subcutaneous injection of tuberculin antigen. Control animals (n = 14) received empty devices. Uveitis was induced with an intravitreal tuberculin antigen injection. A masked observer graded anterior chamber flare, anterior chamber cells, vitreous opacity, and inflammation on histologic sections.

RESULTS

In vitro, the drug was released from both devices in a linear manner. In vivo, treated eyes were significantly less inflamed than untreated eyes (P< or =.02). Inflammation was suppressed to a greater degree with the 0.5-microg/d implant compared with the 0.1-microg/d implant.

CONCLUSION

Sustained-release fluocinolone intravitreal implants suppress ocular inflammation in a rabbit model of severe uveitis.

CLINICAL RELEVANCE

The efficacy demonstrated with the 0.1-microg/d implant provides the rationale for future human studies with lower-release-rate implants than are currently used in noninfectious uveitis clinical trials.

Retisert (Bausch & Lomb/Control Delivery Systems)

Retisert (Envision TD), a sustained release intraocular implant containing fluocinolone acetonide, has been developed and launched in the US by Bausch & Lomb and Control Delivery Systems for the treatment of chronic non-infectious uveitis affecting the posterior segment of the eye.

Ocular pharmacokinetics of fluocinolone acetonide after Retisert intravitreal implantation in rabbits over a 1-year period

PURPOSE

The present study was designed to examine the pharmacokinetics of a fluocinolone acetonide (FA) intravitreal implant in pigmented rabbits.

METHODS

Pigmented rabbits were randomly assigned to receive either a 0.5 mg or 2.0 mg FA intravitreal implant (Retisert). Four animals were sacrificed per time point (2 hours; 2 weeks; and 3, 6, 9, and 12 months after implantation) for FA intraocular levels determination.

RESULTS

In the vitreous, concentration of FA was relatively constant from the first time point, 2 hours, through 1 year, and dose-related, approximately seven- to eight-fold greater in the 2-mg implant. Concentrations of FA were generally higher in the vitreous (11-18 and 75-146 ng/g) and retina (42-87 and 224-489 ng/g) than in the aqueous humor (0.21-1.1 and 2.6-13.0 ng/g) for the 0.5- and 2-mg implants, respectively. Urine and plasma values were below the lower limit of quantitation (200 pg/mL) for all observations, indicating no evidence of systemic absorption.

CONCLUSIONS

In this rabbit study, the Retisert provides relatively constant levels of FA in the posterior pole, which is consistent with previous reports of its clinical utility.

Single-dose study to compare the pharmacokinetics of HFA flunisolide and CFC flunisolide

The hydrofluoroalkane (HFA) formulation of the inhaled corticosteroid flunisolide is a modification of the original chlorofluorocarbon (CFC) formulation. HFA flunisolide replaces CFC with an HFA propellant and uses a built-in spacer in its pressurized metered-dose inhaler. The average HFA flunisolide particle size is 1.2 microm compared with 3.8 microm for the CFC formulation. The smaller particle size improves lung targeting, allowing a reduction in the HFA flunisolide dose relative to CFC flunisolide while maintaining comparable efficacy. In a study of 12 healthy men, pharmacokinetic parameters were determined after single doses of 1000 microg CFC flunisolide delivered without a spacer, 340 microg HFA flunisolide delivered through a spacer, and 516 microg HFA flunisolide delivered without a spacer. A standard noncompartmental analysis of the concentration data was performed and mean (+/- S.D.) pharmacokinetic values were reported. Peak plasma concentrations (observed C(max)) were similar for the three treatments. Area under the curve up to the time corresponding to the last measurable concentration (AUC(0)(-)(tlast)) was similar for the CFC and HFA flunisolide, plus spacer groups (4.4 +/- 1.6 ng x h/mL and 5.0+/- 4.2 ng x h/mL, respectively); however, AUC(0)(-)(tlast) for the HFA flunisolide without spacer group was comparatively lower than for the CFC group (3.5 +/- 1.6 ng x h/mL). Observed C(max) and AUC(0)(-)(tlast) for 6 beta-OH flunisolide, the first-pass metabolite of flunisolide and an indicator of oropharyngeal deposition, were significantly higher in the CFC flunisolide group than in either HFA flunisolide group.

Deposition and pharmacokinetics of flunisolide delivered from pressurized inhalers containing non-CFC and CFC propellants

Our objective was to assess the deposition and pharmacokinetics of a novel formulation of flunisolide (Aerobid, Forest Laboratories) in hydrofluoroalkane (HFA) 134a delivered by pressurized metered dose inhaler (pMDI). The design was a two-way crossover investigation in 12 healthy male subjects comparing HFA-134a flunisolide by pMDI versus pMDI plus 50 mL spacer device. Four of these subjects also took part in a two-way crossover investigation comparing chlorofluorocarbon (CFC) flunisolide pMDI versus pMDI plus Aerochamber holding chamber. The imaging technique of gamma scintigraphy was used to quantify total and regional lung deposition of flunisolide. Plasma levels of flunisolide and its major metabolite (6beta-OH flunisolide) were also determined. The spacer and Aerochamber reduced oropharyngeal deposition dramatically for both the HFA and CFC products (mean 59.8 to 14.9% (p < 0.01) of ex-valve (metered) dose for HFA product; 66.3 to 12.3% (p < 0.01) of ex-valve dose for CFC product) owing to deposition of part of the dose on the walls of the add-on devices themselves. Lung deposition averaged 22.6 and 40.4% (p < 0.01) of the ex-valve dose for the HFA formulation used with pMDI alone and with pMDI plus spacer. Mean lung deposition of the CFC formulation delivered via the Aerochamber (mean 23.4%) was higher than that for the CFC pMDI alone (mean 17.0%), but this difference was not statistically significant. Lung deposition expressed as percentage ex-device (delivered) dose averaged 68.3% for HFA pMDI plus spacer and 19.7% for CFC pMDI. Plasma levels of flunisolide were higher for the pMDI plus spacer than for pMDI alone, reflecting higher lung deposition via the spacer, but plasma levels of the 6beta-OH flunisolide metabolite were higher for the pMDI alone as a consequence of higher oropharyngeal deposition. When delivered via the spacer, pulmonary targeting of the flunisolide HFA formulation was improved compared with the CFC formulation, which should benefit patients by providing satisfactory asthma therapy from a much-reduced delivered dose of flunisolide.

Flunisolide HFA vs flunisolide CFC: pharmacokinetic comparison in healthy volunteers

Two preparations of flunisolide, an inhaled corticosteroid, were compared in a parallel, multiple-dose study of 31 healthy volunteers. The new flunisolide preparation substitutes hydrofluoroalkane (HFA) for chlorofluorocarbon (CFC) as a propellant and incorporates a spacer into its pressurized metered-dose inhaler (pMDI). In this study, subjects were randomly assigned to receive flunisolide CFC 1000 microg bid; flunisolide HFA 170 microg bid; or flunisolide HFA 340 microg bid. Dosing was continued for 13.5 days. Plasma samples were analyzed after the first dose on day 1 and again after 13.5 days of treatment. No significant differences in day 1 dose-adjusted peak plasma concentrations (C(max)) were observed. Dose proportionality in C(max) and area under the concentration--time curves (AUC) was observed for the flunisolide HFA 170 and 340 microg bid groups on days 1 and 14. Day 1 mean dose-adjusted AUC was significantly greater in the flunisolide CFC 1000 microg bid group than in either flunisolide HFA group, indicating greater systemic availability of flunisolide CFC. Oral clearance and volume of distribution were significantly higher for flunisolide CFC than for flunisolide HFA. This may be due to greater oropharyngeal deposition by the flunisolide CFC formulation. Another indicator of greater flunisolide CFC oropharyngeal deposition was observed in C(max) and AUC(0--tlast) values for 6beta-OH flunisolide, the first-pass metabolite of flunisolide. The values of these pharmacokinetic parameters were significantly higher in the flunisolide CFC group than in the 340 microg bid flunisolide HFA group on days 1 and 14. However, this was not the case for cortisol values where flunisolide HFA accounted for less oropharyngeal deposition and more targeted delivery without adverse events. The study demonstrated that flunisolide HFA administered through a pMDI with built-in spacer was safe and well tolerated in healthy volunteers.

Pharmacokinetics of intranasal corticosteroids

Topical administration of corticosteroids can reduce the total dose of corticosteroid required to treat the patient and minimize side effects. This logic has led to the development of intranasal corticosteroids (INCS) for allergic and perennial rhinitis. The second generation of these compounds includes beclomethasone dipropionate, budesonide, flunisolide, fluticasone propionate, mometasone furoate, and triamcinolone acetonide. There is evidence that the INCS are effective in rhinitis; however, there is concern about the potential for these compounds to cause growth suppression. In one study, beclomethasone dipropionate significantly reduced growth in children; however, treatment of children with mometasone furoate nasal spray for 1 year showed no signs of growth suppression. It is evident that the differences among INCS lie in their pharmacokinetics. Structural differences among the various INCS influence their metabolism. The goal of INCS therapy is to have a high ratio of topical to systemic activity. The drug delivery device, absorption of the drug, and drug distribution all contribute to effective topical activity of an INCS. In addition, individual drug metabolism and elimination (half-life and drug clearance) also contribute to the therapeutic index of a drug. Overall, the second-generation INCS cause minimal systemic effects at recommended doses.

Pharmacokinetics of the fluocinolone/5-fluorouracil codrug in the gas-filled eye

PURPOSE

To determine the effect of intraocular gas tamponade on drug levels achieved with the intravitreal sustained-release fluocinolone (FL)/5-fluorouracil (5-FU) codrug pellet.

METHODS

After insertion of a 10-mg codrug pellet into the right eyes of 43 New Zealand white rabbits, perfluoropropane (0.4 mL of 100% C3F8) or a control sham was then injected into the midvitreous cavity. On postoperative days 2, 4, 7, 21, and 42, aqueous samples were collected, the rabbits were killed, and the right eyes were enucleated. The vitreous and remaining codrug pellet were then isolated. Pellet and intravitreal drug levels were determined by high-pressure liquid chromatography.

RESULTS

No measurable drug levels were detected in any of the aqueous samples. Maximal gas expansion occurred by day 4 and partial resorption was observed by days 14 to 21. Vitreous FL and 5-FU levels during C3F8 expansion (day 2) were statistically significantly higher in the gas-filled eyes. On postoperative days 4, 7, 21, and 42, there were no statistically significant differences between FL and 5-FU drug levels in eyes containing C3F8 as compared with control eyes. Pellet codrug, FL, and 5-FU levels over time were similar in gas-filled and control eyes.

CONCLUSIONS

Intraocular gas tamponade does not significantly affect the sustained intravitreal drug levels achieved with the FL/5-FU codrug. If clinically efficacious, the FL/5-FU codrug formulation does not need to be altered to treat proliferative vitreoretinopathy in the presence of intraocular gas.

Safety and pharmacokinetics of an intraocular fluocinolone acetonide sustained delivery device

PURPOSE

To determine the safety and pharmacokinetics of an intraocular fluocinolone acetonide sustained drug delivery device.

METHODS

Nonbiodegradable drug delivery devices containing 2 or 15 mg of a synthetic corticosteroid, fluocinolone acetonide, were constructed. The long-term in vitro release rates of these devices were determined in protein-free buffer or buffer containing 50% plasma protein. Fifteen-milligram devices were also implanted into the vitreous cavities of rabbit eyes. Intravitreal drug levels, the amount of drug remaining in explanted devices, and the release rate of explanted devices were determined over a 1-year time period. Drug toxicity was assessed over this same time period by slit lamp examination, indirect ophthalmoscopy, electroretinography, and histologic examination.

RESULTS

The drug release rates for the 2-mg device, 1.9 +/- 0.25 microg/d, and for the 15-mg device, 2.2 +/- 0.6 microg/d, remained linear over the 6-month and 45-day testing period, respectively. The release rate increased by approximately 20% when devices were transferred from protein-free buffer to buffer that contained protein (P: < 0.0001). Vitreous levels remained fairly constant (0.10-0.21 microg/ml) over a 1-year period. No drug was present in the aqueous humor during this time period. Based on the device release rates, the predicted life span of the 2- and 15-mg devices are 2.7 and 18.6 years, respectively. There was no evidence of drug toxicity by clinical examination, electroretinography, or histologic examination.

CONCLUSIONS

It is feasible to construct a nontoxic fluocinolone acetonide drug delivery device that reproducibly releases fluocinolone acetonide in a linear manner over an extended period. These devices show great promise in the treatment of ocular diseases such as uveitis, which are often managed with chronic corticosteroid therapy.

An interactive algorithm for the assessment of cumulative cortisol suppression during inhaled corticosteroid therapy

The objective of the study was to develop an algorithm based on a pharmacokinetic-pharmacodynamic (PK/PD) modeling approach to quantify and predict cumulative cortisol suppression (CCS) as a surrogate marker for the systemic activity of inhaled corticosteroid therapy. Two Excel spreadsheets, one for single dose and another for steady-state multiple doses of inhaled steroids, were developed for predicting CCS. Four of the commonly used inhaled steroids were chosen for the purposes of simulation: fluticasone propionate (FP), budesonide (BUD), flunisolide (FLU), and triamcinolone acetonide (TAA). Drug-specific PK and PD parameters were obtained from previous single- and multiple-dose studies. In cases in which multiple-dose data were not available, the single-dose data were extrapolated. The algorithm was designed to calculate CCS based on 5 input parameters: name of drug, dose, dosing interval, time(s) of dosing, and type of inhaler device. In addition, a generalized algorithm was set up to calculate CCS based on clearance, volume of distribution, absorption rate, protein binding, pulmonary deposition, oral bioavailability, and unbound EC50 of the corticosteroid of interest. The spreadsheet allowed predictions of CCS for single doses as well as steady-state conditions. A simple method has been developed that facilitates comparisons between various drugs and dosing regimens and has the potential to significantly reduce the number of comparative clinical trials to be performed for evaluating the short-term systemic activity of inhaled corticosteroids.

Binding of glucocorticoids to human nasal tissue in vitro

BACKGROUND

Intranasal application of glucocorticoids is an efficacious treatment of allergic rhinitis and some cases of nonallergic rhinitis. However, no data on binding of glucocorticoids to nasal tissue are available. Pronounced binding of the compound to the target tissue is favorable as it might serve as a local deposit delivering the glucocorticoid to specific receptors and it slows down the efflux of the compound into systemic circulation.

METHODS

Human nasal tissue was incubated with fluticasone propionate, budesonide, flunisolide and beclomethasone-17-monopropionate. Kinetics of binding and redistribution of the tissue-bound fraction into human plasma was monitored.

RESULTS

Binding of glucocorticoids to human nasal tissue was fast and highest for the lipophilic fluticasone propionate, followed by beclomethasone-17-monopropionate. Also, highest concentrations of these lipophilic glucocorticoids remained in nasal tissue after equilibration of drug-saturated tissue with plasma.

CONCLUSIONS

Lipophilic compounds exhibit a high tissue binding and retention which is an important property of topically applied glucocorticoids. It is the basis for prolonged action and low concentration of the compound in systemic circulation.

Pharmacokinetics of flunisolide administered via metered dose inhaler with and without a spacer device and following oral administration

BACKGROUND

After inhalation of a glucocorticoid from a meter dose inhaler (MDI), a certain portion of the delivered dose is deposited in the lungs, and the remainder is deposited in the oropharynx.

OBJECTIVE

To examine the absolute bioavailability of flunisolide given orally via metered dose inhaler, and metered dose inhaler with a commercially available spacer device as well as to determine the fraction of drug deposited in the lungs following inhalation.

METHODS

Twenty-four healthy volunteers were enrolled in the study; twenty-two completed the study. The IRB approved the study protocol, and informed consent was obtained. Volunteers received four treatments: treatment A (MDI), 1.0 mg inhaled flunisolide; treatment B (MDI-S), 1.0 mg inhaled flunisolide with a spacer device; treatment C, 1.0 mg of orally administered flunisolide with 240 mL of water; and treatment D, 1.0 mg intravenous flunisolide by IV push in the antecubital vein over 60 seconds. Plasma and urine flunisolide were quantified by HPLC/mass spectrometry/mass spectrometry.

RESULTS

Flunisolide is a corticosteroid with low oral bioavailability (6.7%), which was found to be lower than previously reported. Similar AUCs were observed between the MDI and MDI-S groups, but by using mass balance equations, it appears that more flunisolide was delivered to the lungs in the MDI-S group (410 microg versus 280 microg). Oropharyngeal deposition was an important difference between the two inhaler groups. Approximately an 11-fold reduction in the oropharyngeal deposition of flunisolide through use of the spacer device was observed.

CONCLUSIONS

Use of a spacer device improved pulmonary delivery of flunisolide by almost 50% and significantly decreased the oropharyngeal exposure to drug.

Comparison of efficacy and safety between flunisolide/AeroChamber and budesonide/turbuhaler in patients with moderate asthma. AER-MD-04 Study Group

BACKGROUND

There is a limited body of evidence comparing the clinical effects of different inhaled corticosteroids in the treatment of asthma. This study compared the safety and efficacy of inhaled flunisolide and budesonide, both with unique delivery systems that may affect clinical response.

OBJECTIVE

This multicenter study was carried out to compare the efficacy and safety of flunisolide, administered via AeroChamber, with budesonide, administered via Turbuhaler, in the treatment of moderate asthma.

METHODS

Patients with moderate asthma, defined as an FEV1 of 40% to 85% of predicted, underwent a 2-week run-in period during which beclomethasone, 750 microg twice daily by MDI, was administered, along with salbutamol prn. Patients (n = 176) were then randomized into two groups. One group received flunisolide administered via AeroChamber, 750 microg (3 puffs), twice daily. The second group received budesonide administered via Turbuhaler, 600 microg (3 puffs), twice daily. All patients took salbutamol prn.

RESULTS

At the end of the 6-week treatment period, there were no significant differences (P > .05 for all comparisons) in efficacy between the groups as evaluated by any efficacy parameter. The treatment groups also did not differ significantly in the number of adverse events or in the incidence of oropharyngeal Candida infection.

CONCLUSION

Flunisolide administered by AeroChamber and budesonide administered via Turbuhaler demonstrate similar efficacy and safety in the treatment of moderate asthma.

Pharmacokinetic/pharmacodynamic evaluation of systemic effects of flunisolide after inhalation

The pharmacokinetics and pharmacodynamics of flunisolide were studied in healthy volunteers after inhalation. In the morning on the day the study began, volunteers inhaled 0.5 mg of flunisolide with and without oral administration of charcoal, or 1 mg, 2 mg, and 3 mg of flunisolide with concomitant administration of charcoal. A placebo group was used to assess the endogenous cortisol, granulocyte, and lymphocyte baseline levels. Flunisolide plasma levels were determined by high-performance liquid chromatography using a tandem mass spectrometer as detector (HPLC/MS/MS). Cortisol plasma levels and differential white blood cell counts were obtained over 12 hours. An integrated pharmacokinetic/pharmacodynamic (PK/PD) model was applied to link the flunisolide plasma concentrations with the effects on lymphocytes, granulocytes, and cortisol. Maximum concentration levels of 3 to 9 ng/mL of flunisolide were observed after 0.2 to 0.3 hours for all of the investigated doses. The terminal half-life ranged from 1.3 to 1.7 hours. There was no statistical difference between treatments in the presence or absence of orally administered charcoal. The pharmacokinetic/pharmacodynamic (PK/PD) models satisfactorily described the time-courses of the effects on granulocytes, lymphocytes, and cortisol suppression. The resulting E50-values (concentrations to induce 50% of the maximum effect) concurred with the reported values of in vitro receptor binding affinities. The duration of the systemic effects were short because of the short half-life of the drug. Cumulative cortisol suppression increased with dose administration and ranged from 20% to 36%. The PK/PD simulations resulted in a smaller degree of cortisol suppression for the drug administered at 10 PM. The cumulative change from baseline was slightly smaller for the effects on granulocytes and lymphocytes than those on cortisol. This information promotes the comparison with other inhaled glucocorticoids.

Efficient delivery to the lungs of flunisolide aerosol from a new portable hand-held multidose nebulizer

In order to provide asthmatic patients with an inhaler that does not use chlorofluorocarbon propellants, a novel multidose hand-held nebulizer (RESPIMAT, Boehringer Ingelheim Ltd.) has been developed. This device delivers 200 x 15 microL metered doses of drug solution, but does not use propellants of any kind. In this study of 10 healthy volunteers, the deposition pattern in the lungs and oropharynx of an ethanolic solution of flunisolide delivered via a prototype III multidose nebulizer has been determined by gamma scintigraphy. A comparison was made with the same dose (250 micrograms) of flunisolide delivered by a pressurized metered dose inhaler (MDI) and MDI plus Inhacort spacer. Mean (SD) whole lung deposition from the multidose nebulizer (39.7 (9.9) % of the metered dose) was significantly higher than that from either MDI (15.3 (5.1) %, P < 0.01) or MDI plus spacer (28.0 (7.0) %, P = 0.01). A mean 10.4% of the dose was recovered from an exhaled air filter for the multidose nebulizer, but less than 2% of the dose for MDI or MDI plus spacer. Oropharyngeal deposition was significantly reduced for the multidose nebulizer (39.9 (9.4) %) compared to MDI (66.9 (7.1) %), but was reduced further for the MDI plus spacer (27.3 (11.3) %). The multidose nebulizer delivers an unusually high percentage of an aerosol dose to the lungs, and it "targets" flunisolide to the lungs more effectively than the MDI. The multidose nebulizer could constitute a viable alternative to MDIs in asthma maintenance therapy.

Deep tissue penetration of bases and steroids after dermal application in rat

The local deep tissue penetration of bases such as diazepam, antipyrine, iodoantipyrine, haloperidol and steroids such as hydrocortisone, fluocinolone acetonide, testosterone and progesterone after dermal application as aqueous solutions was studied in a rat model. The extent of local, as distinct from systemic delivery, for each solute was assessed by comparing the tissue concentrations obtained below a treated site with those in contralateral tissues. Local direct penetration was evident for all solutes below the applied site, although depth of penetration varied between individual solutes. A physiological pharmacokinetic model was employed to estimate local tissue concentrations of various compounds after dermal application.

Topical formulations of fluocinolone acetonide. Are creams, gels and ointments bioequivalent and does dilution affect activity?

The study was done in healthy volunteers to investigate the vasoconstrictor activity of three commercially available formulations of fluocinolone acetonide (Synalar gel, cream and ointment) and to determine whether they were bioequivalent. The influence of dilution of the cream formulation on activity was also examined. Twenty mg of each topical formulation was applied, followed by occlusion for 6 h, and the potency was evaluated by measuring the vasoconstrictor effect using tristimulus colour analysis. The cream formulation was more potent than the ointment, with the gel having intermediate strength. Dilution did not significantly reduce activity. While choice of an appropriate topical corticosteroid formulation largely depends on the nature of the lesions, this study has shown that different formulations of nominally the same concentration have different potencies; dilution up to 1 in 10 produced no significant reduction in potency. The potency classification in the British National Formulary for formulations of Synalar may need revision.

Quantitative vasoconstrictor assay for topical corticosteroids: the puzzling case of fluocinolone acetonide

BACKGROUND

The validity of the vasoconstrictor test has been questioned because of the apparent nonequivalence of some generic corticosteroid products.

OBJECTIVE

Our purpose was to determine the vasoconstrictor activity of a generic 0.025% fluocinolone acetonide ointment by two different methods, dilution by volume and dilution by area of application.

METHODS

Vasoconstrictor activity on a visual 4-point scale was measured in 20 volunteers. Topical fluocinolone acetonide ointment (0.025%) was tested by comparing dilution by volume (1:1, 1:3, and 1:7) in petrolatum and dilution by area of application. Fluocinolone release from the diluted ointments was also measured with an in vitro method.

RESULTS

Dilution by area gave the expected results, a decreasing average vasoconstrictor score; but dilution by volume did not. Both the 1:1 and 1:3 dilutions inexplicably showed greater activity than the full-strength product; this finding was similarly reflected in the in vitro studies that showed a greater rate of drug release from the 1:1 and 1:3 dilutions.

CONCLUSION

Dilution by area provides a useful quantitative assay for comparative vasoconstrictor activity.