Evaluation of the type and frequency of extemporaneous formulations dispensed in hospital and community pharmacies

Background

Extemporaneous compounding is practiced globally by pharmacists to allow for dispensing of personalised doses of medicinal products not commercially available. Extemporaneous compounding must result in a product which is safe and effective. However, data on formulation and expiry of extemporaneous products may not be readily available. Pharmacists access various resources including compounding databases to obtain information on composition, preparation, and expiry of extemporaneous preparations.

Objectives

The aim of this study was to evaluate the type and frequency of extemporaneous compounding in hospital and community pharmacies in the Republic of Ireland (ROI) and to obtain contemporary information on compounding practices and resources used.

Methods

All community and hospital pharmacists registered with the Pharmaceutical Society of Ireland, were invited to participate in an on-line survey. The study was approved by the Royal College of Surgeons in Ireland (RCSI) research ethics committee.

Results

A total of 202 pharmacists responded to the survey, of which 145 were community-based, 52 hospital-based, and 5 practicing in both. On average, hospital and community pharmacists (n = 138) dispensed <2-10 prescriptions for extemporaneous products per month. Pharmacists reported compounding 13 different types of extemporaneous preparations. Of these, dermatological preparations and oral liquid formulations (OLFs) were most commonly compounded. Extemp.ie, an Irish compounding database, was the most frequently used resource for compounding guidance and product expiry.

Conclusions

The results of this study show that extemporaneous compounding is still practiced in hospital and community pharmacies in the ROI. The limited response of 4.6% obtained may reflect that extemporaneous compounding is concentrated in a relatively small number of pharmacies. There remains a clinical need for extemporaneous products in the ROI and extemporaneous compounding continues to be an invaluable skillset for pharmacists.

Oral infliximab nanomedicines for targeted treatment of inflammatory bowel diseases

BACKGROUND AND AIMS

Anti-TNF biological therapies such as infliximab (INF) have revolutionised the treatment of inflammatory bowel diseases (IBD). However, serious adverse effects due to systemic administration can significantly impact patient quality of life, limiting their success. Oral nanomedicines propose an innovative solution to provide local delivery to inflamed gastrointestinal tissues, thereby limiting systemic exposure and enhancing therapeutic efficacy. This study aimed to examine the potential of INF nanomedicines for IBD treatment with a focus on nanoparticle (NP) size to modulate the targeting of INF to the epithelial barrier.

METHODS

Healthy and inflamed in vitro models of the intestinal epithelial barrier were established to examine the cell interaction of PLGA-PEGNPs of varying particle sizes and polydispersities. INF-loaded NPs were prepared by electrostatic interaction of INF with NPs and examined for their therapeutic efficacy in the inflamed epithelial cell barrier model.

RESULTS

NP interaction was significantly enhanced in the inflamed cell barrier model, with increased transport observed for 130 - 300 nm NPs and accumulation of larger NPs (∼600 nm) at the barrier. Delivery of INF directly to the inflamed barrier by ∼600 nm NPs accelerated recovery of barrier integrity and reduced inflammatory cytokine secretion and cytotoxicity in comparison to treatment with INF alone.

CONCLUSIONS

Results from this study show that NP particle size can be used to differentially target and treat the inflamed intestinal barrier. Oral INF nanomedicines of modulated size present a novel strategy for the local, targeted treatment of IBD.

Investigation of the Physical, Chemical and Microbiological Stability of Losartan Potassium 5 mg/mL Extemporaneous Oral Liquid Suspension

Extemporaneous oral liquid preparations are commonly used when there is no commercially available dosage form for adjustable dosing. In most cases, there is a lack of stability data to allow for an accurately assigned shelf life and storage conditions to give greater confidence of product safety and efficacy over its shelf life. The aim of this study was to evaluate the physical, chemical and microbiological stability of an extemporaneous oral liquid suspension of losartan potassium, 5 mg/mL, used to treat paediatric hypertension in Our Lady’s Children’s Hospital Crumlin, Ireland. The losartan content of extemporaneous oral suspensions, prepared with and without addition of water, was measured by UV and confirmed by HPLC analysis. Suspensions were stored at 4 °C and room temperature (RT) and were monitored for changes in; pH, colour, odour, re-dispersibility, Total Aerobic Microbial Count, Total Yeast and Mould Count and absence of E. coli. Results showed that suspensions prepared by both methods, stored at 4 °C and RT, were physically and microbiologically stable over 28 days. Initial losartan content of all suspensions was lower than expected at 80–81% and did not change significantly over the 28 days. HPLC and NMR did not detect degradation of losartan in the samples. Suspensions prepared in water showed 100% losartan content. The reduced initial losartan content was confirmed by HPLC and was related to the acidic pH of the suspension vehicle. Physiochemical properties of the drug are important factors for consideration in the selection of suspension vehicle for extemporaneous compounding of oral suspensions as they can influence the quality, homogeneity and efficacy of these preparations.

Optimising PLGA-PEG Nanoparticle Size and Distribution for Enhanced Drug Targeting to the Inflamed Intestinal Barrier

Oral nanomedicines are being investigated as an innovative strategy for targeted drug delivery to treat inflammatory bowel diseases. Preclinical studies have shown that nanoparticles (NPs) can preferentially penetrate inflamed intestinal tissues, allowing for targeted drug delivery. NP size is a critical factor affecting their interaction with the inflamed intestinal barrier and this remains poorly defined. In this study we aimed to assess the impact of NP particle size (PS) and polydispersity (PDI) on cell interaction and uptake in an inflamed epithelial cell model. Using 10, 55 and 100 mg/mL poly(lactic-co-glycolic acid)-polyethylene glycol (PLGA-PEG), NPs of 131, 312 and 630 nm PS, respectively, were formulated by solvent dispersion. NP recovery was optimised by differential centrifugation to yield NPs of decreased and unimodal size distribution. NP-cell interaction was assessed in healthy and inflamed caco-2 cell monolayers. Results show that NP interaction with caco-2 cells increased with increasing PS and PDI and was significantly enhanced in inflamed cells. Trypan blue quenching revealed that a significant proportion of multimodal NPs were primarily membrane bound, while monomodal NPs were internalized within cells. These results are interesting as the PS and PDI of NPs can be optimised to allow targeting of therapeutic agents to the epithelial membrane and/or intracellular targets in the inflamed intestinal epithelium.

The future of nanomedicine in optimising the treatment of inflammatory bowel disease

There have been major advancements in the treatment of inflammatory bowel disease (IBD) over the past three decades. However despite significant progress, the best available treatments continue to demonstrate variable efficacy in patients and are associated with adverse effects. Therefore there remains an unmet clinical need for ongoing therapeutic advances for IBD. In recent years nanomedicines have emerged as promising diagnostic and therapeutic tools. Nanoparticles in particular show promise to facilitate targeted oral drug delivery in IBD. Here we discuss the pitfalls of current therapies and explore the potential for nanoparticles to improve the treatment of IBD. This review examines the range of conventional and novel therapies which have benefited from nanoparticle-mediated delivery and highlights the proven therapeutic efficacy of this approach in preclinical models. These strategies under development represent a novel and innovative treatment for IBD.

Targeting the 19S proteasomal subunit, Rpt4, for the treatment of colon cancer

Deregulation of the ubiquitin-proteasome pathway has been frequently observed in a number of malignancies. Using quantitative Western blotting of normal and matched tumour tissue, we here identified a significant increase in the 19S proteasome subunit Rpt4 in response to chemoradiation in locally advanced rectal cancer patients with unfavourable outcome. We therefore explored the potential of Rpt4 reduction as a therapeutic strategy in colorectal cancer (CRC). Utilizing siRNA to down regulate Rpt4 expression, we show that silencing of Rpt4 reduced proteasomal activity and induced endoplasmic reticulum stress. Gene silencing of Rpt4 also inhibited cell proliferation, reduced clonogenic survival and induced apoptosis in HCT-116 colon cancer cells. We next developed a cell penetrating peptide-based nanoparticle delivery system to achieve in vivo gene silencing of Rpt4. Administration of Rpt4 siRNA nanoparticles reduced tumour growth and improved survival in a HCT-116 colon cancer xenograft tumour model in vivo. Collectively, our data suggest that inhibition of Rpt4 represents a novel strategy for the treatment of CRC.

Localised controlled release of simvastatin from porous chitosan-gelatin scaffolds engrafted with simvastatin loaded PLGA-microparticles for bone tissue engineering application

Localised controlled release of simvastatin from porous freeze-dried chitosan-gelatin (CH-G) scaffolds was investigated by incorporating simvastatin loaded poly-(dl-lactide-co-glycolide) acid (PLGA) microparticles (MSIMs) into the scaffolds. MSIMs at 10% w/w simvastatin loading were prepared using a single emulsion-solvent evaporation method. The MSIM optimal amount to be incorporated into the scaffolds was selected by analysing the effect of embedding increasing amounts of blank PLGA microparticles (BL-MPs) on the scaffold physical properties and on the in vitro cell viability using a clonal human osteoblastic cell line (hFOB). Increasing the BL-MP content from 0% to 33.3% w/w showed a significant decrease in swelling degree (from 1245±56% to 570±35%). Scaffold pore size and distribution changed significantly as a function of BL-MP loading. Compressive modulus of scaffolds increased with increasing BL-MP amount up to 16.6% w/w (23.0±1.0kPa). No significant difference in cell viability was observed with increasing BL-MP loading. Based on these results, a content of 16.6% w/w MSIM particles was incorporated successfully in CH-G scaffolds, showing a controlled localised release of simvastatin able to influence the hFOB cell proliferation and the osteoblastic differentiation after 11 days.

Intranasal and intravenous administration of octa-arginine modified poly(lactic-co-glycolic acid) nanoparticles facilitates central nervous system delivery of loperamide

Objectives

The potential of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) surface modified with octa-arginine (R8) for central nervous system (CNS) delivery was investigated.

Methods

PLGA NPs containing coumarin-6 or loperamide were surface modified using R8 and characterised for size, zeta potential, drug loading and release. We examined the cellular uptake of NPs in Madin-Darby Canine Kidney (MDCK) cells and CNS delivery of loperamide in a mouse model following intranasal (i.n.) and intravenous (i.v.) administration.

Key findings

NPs were 300–350 nm in diameter and of negative zeta potential which neutralised on R8 conjugation. Cellular uptake of R8-PLGA NPs was rapid compared with PLGA NPs and correlated with a high antinociceptive effect in mice by both the i.n. and i.v. routes. Little antinociceptive effect for PLGA NPs was observed reflecting their slow uptake in the in-vitro cell model.

Conclusion

This study demonstrates the potential of R8-PLGA NPs as carriers of therapeutic agents to the CNS.

Fast disintegrating crystalline solid dispersions of simvastatin for incorporation into orodispersible tablets

AIM

Spray dried solid dispersion (SDP) of crystalline simvastatin (SIM) in a fast disintegrating matrix of superdisintegrants was studied as a method to enhance SIM dispersibility, rheology, compactibility and compressibility for incorporation into orodispersible tablets (ODTs).

MATERIALS AND METHODS

The superdisintegrants investigated were crospovidone (CP), sodium starch glycollate (SSG) and calcium silicate (CS) were spray dried with simvastatin to form SDPs.

RESULTS

The SDPs were characterized and the median particle size of SDPs was similar or greater than the SIM, contributing to good rheology of SDPs, while the low bulk density of SDPs indicated a high compactibility. Interestingly electron micrographs for SDPs showed a CP or CS carrier coating of the SIM crystals, contributing to its rheology. Thermal analysis and X-ray diffraction confirmed that SIM was crystalline in the SDPs and no interaction between SIM and any of the carrier(s) was shown by Fourier transform-infra red. Drug content analysis showed a SIM content of 90-95% in SDPs containing CP or CS, while a higher SIM content of 143% was found in SDP containing SSG. When formulated as ODTs, blend containing SIM SDPs in CP showed ease of tableting, regardless of the turret speed. In comparison, tablet blend consisting of a physical mix (PM) of SIM and CP could only be tableted at the lower turret speed of 7 rpm. ODTs formulated using SIM SDPs in CP showed a higher extent of dissolution, compared to the ODTs containing corresponding PM or the commercially available SIM Zocor(®) tablets (ANOVA, P < 0.05).

CONCLUSION

SDP using disintegrants as carriers may offer an alternative formulation approach for ODTs of poorly soluble drugs.

Application of a novel 3-fluid nozzle spray drying process for the microencapsulation of therapeutic agents using incompatible drug-polymer solutions

The aim of this study was to evaluate a novel 3-fluid concentric nozzle (3-N) spray drying process for the microencapsulation of omeprazole sodium (OME) using Eudragit L100 (EL100). Feed solutions containing OME and/or EL100 in ethanol were assessed visually for OME stability. Addition of OME solution to EL100 solution resulted in precipitation of OME followed by degradation of OME reflected by a colour change from colourless to purple and brown. This was related to the low pH of 2.8 of the EL100 solution at which OME is unstable. Precipitation and progressive discoloration of the 2-fluid nozzle (2-N) feed solution was observed over the spray drying time course. In contrast, 3-N solutions of EL100 or OME in ethanol were stable over the spray drying period. Microparticles prepared using either nozzle showed similar characteristics and outer morphology however the internal morphology was different. DSC showed a homogenous matrix of drug and polymer for 2-N microparticles while 3-N microparticles had defined drug and polymer regions distributed as core and coat. The results of this study demonstrate that the novel 3-N spray drying process can allow the microencapsulation of a drug using an incompatible polymer and maintain the drug and polymer in separate regions of the microparticles.

Physical and structural stability of the monoclonal antibody, trastuzumab (Herceptin®), intravenous solutions

A major limitation of biological therapeutics is their propensity for degradation particularly in aqueous solutions hence resulting in their short shelf-life. In this study, the stability of trastuzumab (Herceptin®) intravenous (i.v.) solutions, an IgG1 monoclonal antibody (mAb), indicated for the treatment of HER2 positive breast cancer, stored under refrigerated conditions, was evaluated over 28 days. No change in visual appearance or average particle size was observed. The pH values of the trastuzumab i.v. solutions remained stable over time. Interestingly, no change in trastuzumab monomer concentration was observed throughout the 28-day study, as determined by SEC-HPLC. SDSPAGE showed only a monomer band corresponding to the molecular weight of trastuzumab. Circular dichroism spectra obtained following 28-day storage demonstrated integrity of the secondary structural conformation of trastuzumab. Results from this study show that trastuzumab i.v. solutions remain physically and structurally stable on storage at 2-8°C for 28 days. These findings suggest that trastuzumab in solution may not be as sensitive to degradation as expected for a mAb and therefore may have important implications in extending trastuzumab shelf life for clinical use and reducing associated healthcare cost.

Comparative evaluation of the degree of pegylation of poly(lactic-co-glycolic acid) nanoparticles in enhancing central nervous system delivery of loperamide

Objectives

In this study, we examined the relative cellular uptake of nanoparticles (NPs) formulated using poly(lactic-co-glycolic acid) (PLGA) polymers with increasing degree of pegylation (PLGA-PEG) and their potential to deliver loperamide to the brain of a mouse.

Method

NPs containing coumarin-6 or loperamide HCl were formulated using PLGA and PLGA-PEG, with PEG content of 5–15%, by the solvent evaporation method. NPs were characterised for size, surface charge, morphology, encapsulation efficiency and drug release. Cellular uptake of coumarin-6 NPs was examined in Caco-2 monolayers using confocal microscopy and central nervous system (CNS) delivery of loperamide HCl from the NPs was examined following intranasal administration in a mouse model.

Key findings

No difference in NP characteristics was observed, irrespective of degree of pegylation, except for the surface charge which increased with increasing PEG content. PLGA-PEG NPs were found to have increased cellular uptake in comparison to PLGA NPs. Interestingly, this pattern was reflected in the CNS delivery of loperamide HCl in the mouse model.

Conclusion

The results from this study show that PLGA-PEG NPs have the potential to act as carriers for the noninvasive administration of therapeutic agents to the brain and possibly across other physiological barriers.

Stability of an alternative extemporaneous captopril fast-dispersing tablet formulation versus an extemporaneous oral liquid formulation

BACKGROUND

Administration of medications to pediatric patients is challenging because many drugs are not commercially available in appropriate dosage formulations and/or strengths. Consequently, these drugs are prepared extemporaneously as oral liquid (OL) formulations using marketed tablets or capsules. In many cases, the stability of these extemporaneous preparations, which may affect their tolerability, has not been documented. An alternative extemporaneous solid formulation, such as a fast-dispersing tablet (FDT), may offer enhanced stability as well as dosing flexibility because it may be administered as an orodispersible tablet or as a reconstituted suspension/solution. Although FDTs are available increasingly as patient-friendly oral dosage formulations, and their simple method of manufacture can be applied to extemporaneous formulations, such applications have not been explored to date.

OBJECTIVES

The use of extemporaneous captopril OL formulations in hospitals in Ireland was surveyed, and the stability of the most commonly used captopril formulation (reference) was investigated and compared with that of a newly available extemporaneous FDT formulation.

METHODS

The survey was carried out in 120 hospitals in the Republic of Ireland. The 56-day stability of the most commonly used formulation was compared with that of a newly available extemporaneous captopril FDT preparation. The captopril content of the formulations was measured by high-performance liquid chromatography analysis. Formulations were also monitored for changes in appearance, including color; odor; and pH (OLs only).

RESULTS

The survey showed that extemporaneously prepared captopril OLs were extensively used, particularly in specialist children's hospitals. The most commonly used preparation was a xanthan gum-based oral suspension. Analysis of these OL preparations showed the OLs to have been stable up to day 7, but that the captopril concentration decreased to 72% to 84% at day 14 and to 59% to 68% at day 56; this decrease was accompanied by a pungent odor suggestive of captopril oxidation. In contrast, FDT formulations demonstrated greater stability, with 96% of captopril present at day 56.

CONCLUSIONS

The results of this study support only a 7-day stability for the currently dispensed captopril OL in hospitals in Ireland. In contrast, a stability of at least 56 days was shown with the FDTs. The FDTs may represent an alternative and convenient oral solid extemporaneous preparation of captopril and, potentially, other extemporaneous pediatric medications.

Effect of a disintegration mechanism on wetting, water absorption, and disintegration time of orodispersible tablets

The aim of this study was to evaluate the influence of disintegration mechanism of various types of disintegrants on the absorption ratio (AR), wetting time (WT), and disintegration time (DT) of orodispersible tablets (ODTs). ODTs were prepared by direct compression using mannitol as filler and disintegrants selected from a range of swellable, osmotic, and porous disintegrants. Tablets formed were characterized for their water AR, WT, and DT. The porosity and mechanical strength of the tablets were also measured. Results show that the DT of formulated ODTs was directly related to the WT and was a function of the disintegration mechanism of the disintegrant used. The lowest WT and DT were observed for tablets formulated using the osmotic disintegrant sodium citrate and these tablets also showed the lowest AR and porosity. The wetting and disintegration of tablets containing the highly swellable disintegrant, sodium starch glycollate, was slowest despite their high water AR and high tablet porosity. Rapid wetting and disintegration of ODTs were therefore not necessarily related to the porosity of the tablets.

Investigation of a novel 3-fluid nozzle spray drying technology for the engineering of multifunctional layered microparticles

OBJECTIVE

To examine the potential of a novel 3-fluid nozzle spray drying technology to formulate differentiated layered microparticles (MPs) of diclofenac sodium (DFS)/ethyl cellulose (EC).

METHODS

DFS/EC MPs were formulated using the inner and/or outer nozzles of a novel 3-fluid nozzle and compared with MPs formed using conventional (2-fluid) spray drying. MPs were characterised for particle size and for morphology by TEM and SEM. Distribution of DFS and EC of MPs was analysed by FT-IR and DSC. A two-factor, three-level (3(2)) factorial design was applied to investigate the effect and interaction of total feed solid content (TSC) and feed flow rate (FFR) on MP size, D(50%) and D(90%), bulk density and MP yield.

RESULTS

Interestingly, TEM demonstrated that MPs formed by 3-fluid nozzle spray drying showed a heterogeneous internal morphology consisting of a core and coat, characteristic of a microcapsule. In comparison, MPs from conventional spray drying showed a homogeneous internal morphology, characteristics of a matrix system. This differential distribution of DFS/EC was supported by FT-IR and DSC. Results of multiple linear regression analysis showed a linear relationship for the effect of TSC and FFR on all responses except for D(50%) where a quadratric model was valid. The effect of TSC/FFR on MP size and yield was similar to conventional spray drying.

CONCLUSION

The novel 3-fluid nozzle spray drying offers a new method of designing layered microparticles or microcapsules which can have wide applications from drug stabilisation to controlled drug delivery and targeting.

Investigation of the interaction of biodegradable micro- and nanoparticulate drug delivery systems with platelets

Objectives

Biodegradable micro- and nanoparticles are being increasingly investigated for drug delivery and targeting of therapeutics. The size and surface properties of these particles are important factors influencing their interaction and uptake by various cells, tissues and organs. Optimising these properties, to enhance cellular uptake, may increase their potential for interaction with other physiological components such as platelets resulting in platelet activation and inappropriate thrombus formation. The aim of this study was to investigate the potential interaction of particulates with platelets.

Methods

Biodegradable micro- and nanoparticles based on poly-lactide-co-glycolide (PLGA), poly-lactide-co-glycolide–macrogol (PLGA-macrogol) and chitosan were prepared using solvent evaporation, spray drying or solvent dispersion techniques.

Key findings

Microparticles formulated had a median diameter (D50%) of 2–9 µm, while nanoparticles had an average diameter of 100–500 nm. The surface morphology ranged from smooth and spherical to irregular depending on polymer and preparation method used. Particles, reconstituted in the concentration range of 0.1–500 µg/ml, were tested for their ability to induce or inhibit platelet aggregation. No effects on either induction of platelet activity or inhibition of aggregation were detected.

Conclusions

None of the particles examined were found to alter platelet activity. These results suggested that the biodegradable micro- and nanoparticles tested were safe for use as potential drug carriers of therapeutic agents.

Influence of Formulation Variables on the Morphology of Biodegradable Micropartieles Prepared by Spray Drying

The preparation of microparticles of the biodegradable poly-DL-lactide (PLA) and polylactide-co-glycolide (PLGA) polymers using spray-drying technology was studied. Formulation parameters investigated include polymer type, polymer molecular weight, polymer concentration, and viscosity. Microparticles were characterized using electron microscopy, particle size analysis, and gel permeation chromatography. Kinematic viscosity was determined for each of the sprayed polymer solutions. Polymer molecular weight and polymer concentration were found to be important parameters when preparing PLA and PLGA microparticles using spray-drying technology.

Influence of particle size and dissolution conditions on the degradation properties of polylactide-co-glycolide particles

Polymer degradation usually plays a crucial role in drug release from sustained release polyester systems, therefore in order to elucidate the mechanism governing release, it appears essential to analyse the in vitro degradation behaviour of these devices. In this study the influence of processing conditions, particle characteristics and release media temperature on the degradation of PLGA spherical particles were examined. It was found that a linear relationship between the degradation rate and particle size existed, with the larger particles degrading fastest. In smaller particles degradation products formed within the particle can diffuse easily to the surface while in larger particles degradation products have a longer path to the surface of the particle during which autocatalytic degradation of the remaining polymer material can occur. The influence of release media temperature on the degradation of PLGA particles was also examined. At lower incubation temperatures PLGA microparticles showed an induction period after which polymer degradation proceeded. The rate of polymer degradation was found to increase with increasing incubation temperature. The polymer erosion profile was fitted to the Prout-Tompkins equation and the rate constants were used to determine the activation energy of PLGA hydrolysis.

Binding and uptake of biodegradable poly-DL-lactide micro- and nanoparticles in intestinal epithelia

The use of biodegradable particles as oral delivery vehicles for macromolecular drugs was investigated. We evaluated the binding, uptake and absorption of poly-dl-lactide (PLA) micro- and nanoparticles in Caco-2 monolayers and in ileal tissue and gut associated lymphoid tissue (GALT) of anaesthetised rats and rabbits. Using a range of experimental techniques, we found that approximately 10% of administered micro- and nanoparticles were adsorbed to the apical membranes of each of the five intestinal models. Nanoparticles were found to be absorbed better than microparticles. Overall, little discrimination in uptake patterns was evident between Peyer's patch (PP) and non-PP tissue while rat ileum showed a greater uptake capacity than rabbit. Our results show that uptake of PLA particles was low capacity, size-dependent and predominantly transcellular in all systems. A low proportion of the apically-bound particles was absorbed, with uptake exclusion evident for particles >4microm. The affinity of PLA particles for intestinal epithelia and GALT needs to be greatly enhanced in order to achieve improved oral bioavailability of macromolecules.

Release kinetics of fluphenazine from biodegradable microspheres

Fluphenazine-loaded microspheres were prepared using biodegradable lactide and lactide-co-glycolide polymers. Sustained release of fluphenazine was achieved with fluphenazine loadings of up to 30 per cent in both the lactide and lactide-co-glycolide polymers. Fluphenazine release from microspheres was found to increase with increasing drug loading and was most rapid from the poly-L-lactide-co-glycolide microspheres. The release profiles showed a 'lag' period followed by an accelerating release phase and in some cases a decay period, i.e. the release profiles were sigmoidal and fitted the Prout-Tomkins equation (Prout and Tompkins 1944). Consequently it was considered that polymer degradation, the primary rate-determining step controlling drug release, occurred by a mechanism involving propagation of active sites, drug release reflecting the spread of this degradation throughout the polymer.