Accuracy of intravenous and enteral preparations involving small volumes for paediatric use: a review

BACKGROUND

Children often need to be administered very small volumes of medicines that are authorised for use in adults. Neonatal drug delivery is particularly challenging, and doses are often immeasurable with the equipment currently available.

AIM

To summarise research to date on the accuracy of intravenous and enteral medicine preparation requiring small volumes (<0.1 mL), with a focus on paediatric use and to identify areas for further work.

METHOD

Twenty-three publications were identified for the narrative review via: Web of Science (1950-2016), Cumulative Index to Nursing and Allied Health Literature (1976-2016), Excerpta Medica Database (1974-2016) and International Pharmaceutical Abstracts (1970-2016) searches. Nine additional papers were identified through backward citation tracking and a further 17 were included from the personal knowledge of the review team.

RESULTS

Measurement of volumes (<0.1 mL), for enteral and intravenous dosing, accounts for 25% of medicine manipulations within paediatric hospitals. Inaccuracies are described throughout the literature with dose administration errors attributed to technique, calculation, dilution and problems associated with equipment. While standardised concentrations for intravenous infusion and drug concentrations that avoid measurement of small volumes would ameliorate problems, further work is needed to establish accurate methods for handling small volumes during the administration of medicines to children and risk minimisation strategies to support staff involved are also necessary.

CONCLUSIONS

This review has revealed a paucity of information on the clinical outcomes from problems in measuring small volumes for children and highlighted the need for further work to eliminate this source of inaccurate dosing and potential for medication error.

Content uniformity of quartered hydrocortisone tablets in comparison with mini-tablets for paediatric dosing

OBJECTIVES

Children requiring cortisol replacement therapy are often prescribed hydrocortisone doses of 2.5 mg, but as this is commercially unavailable 10 mg tablets, with functional break lines, are split commonly in an attempt to deliver the correct dose. This study aimed to determine the dose variation obtained from quartered hydrocortisone tablets when different operators performed the splitting procedure and to ascertain whether better uniformity could be attained from mini-tablets as an alternative formulation.

METHODS

Hydrocortisone 10 mg tablets were quartered by four different operators using a standard pill splitter. Hydrocortisone 2.5 mg mini-tablets (3 mm diameter) were formulated using a wet granulation method and manufactured using a high-speed rotary press simulator. The weight and content uniformity of the quartered tablets and mini-tablets were assessed according to pharmacopoeial standards. The physical strength and dissolution profiles of the mini-tablets were also determined.

RESULTS

More than half of all quartered 10 mg tablets were outside of the ±10% of the stated US Pharmacopoeia hydrocortisone content (mean 2.34 mg, SD 0.36, coefficient of variation (CV) 15.18%) and more than 40% of the quartered tablets were outside the European Pharmacopoeia weight variation. Robust mini-tablets (tensile strengths of >4 MPa) were produced successfully. The mini-tablets passed the pharmacopoeial weight and content uniformity requirements (mean 2.54 mg, SD 0.04, CV 1.72%) and drug release criteria during in vitro dissolution testing.

CONCLUSION

This study confirmed that quartering 10 mg hydrocortisone tablets produces unacceptable dose variations and that it is feasible to produce 3 mm mini-tablets containing more accurate doses for paediatric patients.

Inpatient prescribing systems used in NHS Acute Trusts across England: a managerial perspective

Objective

The individualised patient prescription chart, either paper or electronic, is an integral part of communication between healthcare professionals. The aim of this study is to ascertain the extent to which different prescribing systems are used for inpatient care in acute hospitals in England and explore chief pharmacists' opinions and experiences with respect to electronic prescribing and medicines administration (EPMA) systems.

Method

Audio-recorded, semistructured telephone interviews with chief pharmacists or their nominated representatives of general acute hospital trusts across England.

Results

Forty-five per cent (65/146) of the chief pharmacists agreed to participate. Eighteen per cent (12/65) of the participants interviewed stated that their trust had EPMA systems fully or partially implemented on inpatient wards. The most common EPMA system in place was JAC (n=5) followed by MEDITECH (n=3), iSOFT (n=2), PICS (n=1) and one in-house created system. Of the 12 trusts that had EPMA in place, 4 used EPMA on all of their inpatient wards and the remaining 8 had a mixture of paper and EPMA systems in use. Fifty six (86% 56/65) of all participants had consulted the standards for the design of inpatient prescription charts. From the 12 EPMA interviews qualitatively analysed, the regulation required to provide quality patient care is perceived by some to be enforceable with an EPMA system, but that this may affect accuracy and clinical workflow, leading to undocumented, unofficial workarounds that may be harmful.

Conclusions

The majority of inpatient prescribing in hospital continues to use paper-based systems; there was significant diversity in prescribing systems in use. EPMA systems have been implemented but many trusts have retained supplementary paper drug charts, for a variety of medications. Mandatory fields may be appropriate for core prescribing information, but the expansion of their use needs careful consideration.

The impact of food components on the intrinsic dissolution rate of ketoconazole

To accurately predict the in vivo performance of drugs from an in vitro dissolution test, the dissolution conditions used are supposed to be similar to those present in the gastrointestinal milieu. Post-prandial gastric fluid contains partially digested food mixtures consisting of fat, protein and carbohydrate. Despite this, the compendia dissolution medium recommended to simulate the gastric fluid is still composed of a simple solution of hydrochloric acid and sodium chloride with or without the addition of pepsin. Therefore, in this investigation, biorelevant dissolution media were developed to evaluate the impact of food constituents; milk with different fat contents, egg albumin, gelatin, casein, gluten, carbohydrates and amino acids on the intrinsic dissolution behavior of ketoconazole. Most of the food additives that were evaluated enhanced the apparent solubility of the drug but to different extents. The greatest enhancement in dissolution was observed in media containing either neutral amino acids or media based on milk mixtures. The formation of complexes between the drug and the additives most likely accounted for the solubilizing effect and in milk-containing media, the effect was attributed to the whole complex structure of milk rather than simply its fat content. These results highlight the potential effect of the type of ingested meal on drug dissolution and subsequent bioavailability.

The effect of HPMC particle size on the drug release rate and the percolation threshold in extended-release mini-tablets

The particle size of HPMC is a critical factor that can influence drug release rate from hydrophilic matrix systems. Percolation theory is a statistical tool which is used to study the disorder of particles in a lattice of a sample. The percolation threshold is the point at which a component is dominant in a cluster resulting in significant changes in drug release rates. Mini-tablets are compact dosage forms of 1.5-4 mm diameter, which have potential benefits in the delivery of drug to some patient groups such as pediatrics. In this study, the effect of HPMC particle size on hydrocortisone release and its associated percolation threshold for mini-tablets and tablets was assessed. For both mini-tablets and tablets, large polymer particles reduced tensile strength, but increased the drug release rate and the percolation threshold. Upon hydration, compacts with 45-125 μm HPMC particles formed a strong gel layer with low porosity, reducing hydrocortisone release rates. In comparison, faster drug release rates were obtained when 125-355 µm HPMC particles were used, due to the greater pore sizes that resulted in the formation of a weaker gel. Using 125-355 µm HPMC particles increased the percolation threshold for tablets and to a greater extent for mini-tablets. This work has demonstrated the importance of HPMC particle size in ER matrices, the effects of which are even more obvious for mini-tablets.

Transformation in the pharmaceutical industry--a systematic analysis of operational evidence

Through systematic collection and trending of pharmaceutical data, operational evidence to verify existence of 14 factors affecting the ongoing pharmaceutical transformation has been compiled. These 14 factors are termed transformation triggers. The theoretical evidence in support of these triggers is carried forward from a systematic review of the literature that was conducted previously. Trends in operational evidence and the associated theoretical evidence were compared to identify areas of similarity and contrast. Areas of strong correlation between theoretical evidence and operational evidence included four transformation triggers: a fully integrated pharma network, personalized medicine, translational research, and pervasive computing. Key areas of contrast included three transformation triggers-namely, healthcare management focus, adaptive trials, and regulatory enforcement-for which the operational evidence was stronger than the theoretical evidence.

LAY ABSTRACT

The intent of this paper is to provide proof to demonstrate if there is any operational evidence that supports the 14 transformation triggers previously identified during the theoretical part of this research. The theoretical evidence for these triggers was carried forward to this paper for study from an operational perspective. The practical evidence established in this paper was compared with the corresponding theoretical evidence to identify areas of similarity and difference. This resulted in four triggers that had strong relationship between operational and theoretical evidence; they are a fully integrated pharma network, personalized medicine, translational research, and pervasive computing. The areas of difference included three transformation triggers for which the operational evidence was stronger than the theoretical evidence. These were healthcare management focus, adaptive trials, and regulatory enforcement.

Characterization of the evolution of the pharmaceutical regulatory environment

This paper is part of a research study that is intended to identify pharmaceutical quality risks induced by the ongoing transformation in the industry. This study establishes the current regulatory context by characterizing the development of the pharmaceutical regulatory environment. The regulatory environment is one of the most important external factors that affects a company's organization, processes, and technological strategy. This is especially the case with the pharmaceutical industry, where its products affect the quality of life of the consumers. The quantitative analysis of regulatory events since 1813 and review of the associated literature resulted in identification of six factors influencing the regulatory environment, namely public health protection, public health promotion, crisis management, harmonization, innovation, and modernization. From 1813 to the 1970s the focus of regulators was centered on crisis management and public health protection-a basic mission that has remained consistent over the years. Since the 1980s a gradual move in the regulatory environment towards a greater focus on public health promotion, international harmonization, innovation, and agency modernization may be seen.

LAY ABSTRACT

The pharmaceutical industry is currently going through changes that affect the way it performs its research, manufacturing, and regulatory activities. The impact of these changes on the approaches to quality risk management requires more understanding. The authors are engaged in research to identify elements of the changes that influence pharmaceutical quality. As quality requirements are an integral part of the pharmaceutical regulations, a comprehensive understanding of these regulations is seen as the first step. The results of this study show that (i) public health protection, public health promotion, crisis management, harmonization, innovation, and modernization are factors that affect regulations in the pharmaceutical industry; (ii) the regulators' main mission of public health protection has remained a constant feature over the years; and (iii) since the 1970s other factors such as public health promotion, international harmonization, innovation, and agency modernization are playing more important role in regulatory agency thinking and actions.

Manipulation of drugs to achieve the required dose is intrinsic to paediatric practice but is not supported by guidelines or evidence

Background

A lack of age-appropriate formulations can make it difficult to administer medicines to children. A manipulation of the dosage form may be required to achieve the required dose. This study aimed to describe medicines that are manipulated to achieve the required dose in paediatric practice.

Method

A structured, undisguised observational study and postal survey. The observational study investigated drug manipulations occurring in clinical practice across three sites. The questionnaire, administered to a sample of paediatric nurses throughout the UK, surveyed manipulations conducted and nurses’ experiences and views.

Results

The observational study identified 310 manipulations, of which 62% involved tablets, 21% were intravenous drugs and 10% were sachets. Of the 54 observed manipulations 40 involved tablets with 65% of the tablets being cut and 30% dispersed to obtain a smaller dose. 188 manipulations were reported by questionnaire respondents, of these 46% involved tablets, 12% were intravenous drugs, and 12% were nebuliser solutions. Manipulations were predominantly, but not exclusively, identified in specialist clinical areas with more highly dependent patients. Questionnaire respondents were concerned about the accuracy of the dose achieved following manipulations and the lack of practice guidance.

Conclusion

Manipulations to achieve the required dose occur throughout paediatric in-patient settings. The impact of manipulations on the efficacy of the drugs, the accuracy of the dose and any adverse effects on patients is not known. There is a need to develop evidence-based guidance for manipulations of medicines in children.

Transformation in the pharmaceutical industry: transformation-induced quality risks--a survey

This paper is the fourth in a series that explores ongoing transformation in the pharmaceutical industry and its impact on pharmaceutical quality from the perspective of risk identification. The aim of this paper is to validate proposed quality risks through elicitation of expert opinion and define the resultant quality risk model. Expert opinion was obtained using a questionnaire-based survey with participants with recognized expertise in pharmaceutical regulation, product lifecycle, or technology. The results of the survey validate the theoretical and operational evidence in support of the four main pharmaceutical transformation triggers previously identified. The quality risk model resulting from the survey indicated a firm relationship between the pharmaceutical quality risks and regulatory compliance outcomes during the marketing approval and post-marketing phases of the product lifecycle and a weaker relationship during the pre-market evaluation phase.

LAY ABSTRACT

In this paper through conduct of an expert opinion survey the proposed quality risks carried forward from an earlier part of the research are validated and resultant quality risk model is defined. The survey results validate the theoretical and operational evidence previously identified. The quality risk model indicates that transformation-related risks have a larger regulatory compliance impact during product approval, manufacturing, distribution, and commercial use than during the development phase.

Transformation in the pharmaceutical industry--a systematic review of the literature

The evolutionary development of pharmaceutical transformation was studied through systematic review of the literature. Fourteen triggers were identified that will affect the pharmaceutical business, regulatory science, and enabling technologies in future years. The relative importance ranking of the transformation triggers was computed based on their prevalence within the articles studied. The four main triggers with the strongest literature evidence were Fully Integrated Pharma Network, Personalized Medicine, Translational Research, and Pervasive Computing. The theoretical quality risks for each of the four main transformation triggers are examined, and the remaining ten triggers are described.

LAY ABSTRACT

The pharmaceutical industry is currently going through changes that affect the way it performs its research, manufacturing, and regulatory activities (this is termed pharmaceutical transformation). The impact of these changes on the approaches to quality risk management requires more understanding. In this paper, a comprehensive review of the academic, regulatory, and industry literature were used to identify 14 triggers that influence pharmaceutical transformation. The four main triggers, namely Fully Integrated Pharma Network, Personalized Medicine, Translational Research, and Pervasive Computing, were selected as the most important based on the strength of the evidence found during the literature review activity described in this paper. Theoretical quality risks for each of the four main transformation triggers are examined, and the remaining ten triggers are described.

Providing Quality Palliative Care in End-Stage Alzheimer Disease

Providing quality palliative care is a daunting task profoundly impacted by diminished patient capacity at the end of life. Alzheimer disease (AD) is a disorder that erases our memories and is projected to increase dramatically for decades to come. By the time the patients with AD reach the end stage of the disease, the ability of patients to provide pertinent subjective complaints of pain and discomfort would have vanished. Historical perspectives of palliative care, exploration of the AD process, ethical issues, and crucial clinical considerations are provided to improve the understanding of disease progression and quality of care for patients with end-stage AD.

Grief experiences of 3 caregiving wives of veterans with dementia

Three wives share their experiences of caregiving for husbands with dementia. The 3 husbands, aged 51, 71, and 84, developed dementia following years of devoted military service. To present lived experiences of caregiving wives', meanings attributed to caregiving are investigated, variations in caregiving and grieving experiences are explored, and therapeutic implications are offered. Through case study approach and with issues of caregiver grief considered, we introduce life course and ambiguous loss theoretical perspectives. Emergent qualitative themes and quantitative inventory ratings indicate significant differences in caregiver grief response depend on care-recipient age. Practice implications and directions for future care recipient, age-related research are presented.

The manipulation of drugs to obtain the required dose: systematic review

AIM

To describe the development of a systematic review protocol that maps the evidence relating to drug manipulations conducted to obtain the required dose. This process included defining a search strategy and methods to assess the quality and to synthesize the evidence retrieved.

BACKGROUND

Economic constraints mean that marketed formulations may not meet the needs of all patients. Consequently, it is sometimes necessary to manipulate marketed products with the aim of obtaining the required dose. Most clinical practice appears to be guided by ad hoc approaches and informal literature reviews.

METHODS

This systematic review protocol has been designed to identify the evidence available on drug manipulation. The review aims to identify what evidence is available and where the gaps appear in the current evidence. This report describes the challenges of developing a systematic review in an area that potentially involves many drugs and considers outcomes other than effectiveness. In particular, searches required the use of non-specific terms and the iterative development of a complex search strategy. The development of quality assessment criteria is also described. Funding commenced in April 2009.

DISCUSSION

The systematic review described here will capture a broad selection of research about drug manipulations and may also be of interest to those conducting reviews in broad remit subject areas that are not easy to define using accepted terminology.

The use of hypromellose in oral drug delivery

Hypromellose, formerly known as hydroxypropylmethylcellulose (HPMC), is by far the most commonly employed cellulose ether used in the fabrication of hydrophilic matrices. Hypromellose provides the release of a drug in a controlled manner, effectively increasing the duration of release of a drug to prolong its therapeutic effect. This review provides a current insight into hypromellose and its applicability to hydrophilic matrices in order to highlight the basic parameters that affect its performance. Topics covered include the chemical, thermal and mechanical properties of hypromellose, hydration of the polymer matrices, the mechanism of drug release and the influence of tablet geometry on drug-release rate. The inclusion of drug-release modifiers within hypromellose matrices, the effects of dissolution media and the influence of both the external environment and microenvironment pH within the gel matrix on the properties of the polymer are also discussed.

Effect of lubricant type and concentration on the punch tip adherence of model ibuprofen formulations

A model formulation, comprising ibuprofen and direct compression lactose (Tablettose 80) was used to assess the influence of two lubricants, magnesium stearate and stearic acid, on punch tip adherence. Lubricant concentrations were varied from 0.25% to 2% w/w. Formulations in the presence and absence of 0.5% w/w colloidal silica (Aerosil 200) were examined, to assess the influence of the glidant on the anti-adherent effects of the lubricants. Differential scanning calorimetry (DSC) was used to examine the effect of the lubricants on the melting temperature of ibuprofen. Tablets were compacted using a single punch tablet press at 10 kN using hard chrome-plated punches or at 40 kN using uncoated steel punches, tooling was 12.5-mm diameter in each case. The upper punch faces were characterized by obtaining Taylor Hobson Talysurf surface profiles. Following compaction, ibuprofen attached to the face was quantified by spectroscopy. At low concentrations of each lubricant, the levels of sticking observed were similar. Whilst sticking increased at magnesium stearate concentrations above 1%, sticking with stearic acid remained relatively constant at all concentrations. DSC revealed that the melting temperature of ibuprofen was lowered by the formation of eutectic mixtures with both lubricants. However, the onset temperature of melting and melting point were lowered to a greater extent with magnesium stearate compared with stearic acid. When using uncoated tooling at 40 kN, the deleterious effects of magnesium stearate on the tensile strength of the tablets also contributed to sticking. When using chrome-plated punches at 10 kN, the tensile strength reduction by the presence of magnesium stearate was less pronounced, as was the level of sticking.

Effect of punch tip geometry and embossment on the punch tip adherence of a model ibuprofen formulation

The sticking of a model ibuprofen-lactose formulation with respect to compaction force, punch tip geometry and punch tip embossment was assessed. Compaction was performed at 10, 25 or 40 kN using an instrumented single-punch tablet press. Three sets of ‘normal’ concave punches were used to evaluate the influence of punch curvature and diameter. The punches were 10, 11 and 12 mm in diameter, respectively. The 10-mm punch was embossed with a letter ‘A’ logo to assess the influence of an embossment on sticking. Flat-faced punches (12.5 mm) were used for comparison with the concave tooling. Surface profiles (Taylor Hobson Talysurf 120) of the upper punch faces were obtained to evaluate the surface quality of the tooling used. Following compaction, ibuprofen attached to the upper punch face was quantified by spectroscopy. Increasing punch curvature from flat-faced punches to concave decreased sticking. Altering punch diameter of the concave punches had no effect on sticking when expressed as μg mm−2. The embossed letter ‘A’ logo increased sticking considerably owing to the probable concentration of shear stresses at the lateral faces of the embossed logo.

Effects of surface roughness and chrome plating of punch tips on the sticking tendencies of model ibuprofen formulations

The sticking of three model ibuprofen–lactose formulations with respect to compaction force and the surface quality of the upper punch were assessed. Compaction was performed at 10, 25 or 40 kN using an instrumented single-punch tablet press. Two sets of 12.5-mm flat-faced punches were used to evaluate the influence of surface quality. A third set of chrome-plated tooling was also used. Surface profiles (Taylor Hobson Talysurf 120) of the normal tooling upper punches indicated a large difference in quality. The punches were subsequently classified as old (Ra = 0.33 μm) or new (Ra = 0.04 μm) where Ra is the mean of all positive deviations from zero. Surface profiles of sample tablets were also obtained. Following compaction, ibuprofen attached to the face was quantified by spectroscopy. Punch surface roughness, compaction force and the blend composition were all significant factors contributing to sticking. Chrome plating of punch faces increased sticking at a low compaction force but decreased sticking at higher forces. Surface roughness of the tablets did not correlate with the corresponding data for sticking, indicating that this is not a suitable method of quantifying sticking.

In vitro evaluation of the dissolution behaviour of itraconazole in bio-relevant media

Drugs in the gastrointestinal tract are exposed to a medium of partially digested food, comprising mixtures of fat, protein and carbohydrate. The dissolution behaviour of itraconazole was evaluated in bio-relevant media which were developed to take this into account. Media containing milk with different fat contents, protein (albumin, casein, gluten and gelatin), carbohydrates (glucose, lactose and starch) and amino acids (lysine, glycine, alanine and aspartic acid) to mimic a digested meal and bile components (sodium taurocholate and lecithin) to represent a key endogenous digestive material were investigated. The effect of medium composition on the intrinsic dissolution rate of itraconazole was evaluated as this drug has extremely poor solubility and its bioavailability is affected by food. Dissolution tests were carried out in simple compendial media based on dilute solutions of hydrochloric acid or neutral solutions of phosphate buffer and in more complex media containing the dietary components. The data obtained showed that most of the dietary components enhanced the solubility compared to simulated gastric fluid (SGF) but to differing extents. The greatest increase in dissolution was observed with the addition of milk and albumin although an increase was also seen with other proteins, amino acids and simulated gastrointestinal fluids.

An in vitro evaluation of fenugreek mucilage as a potential excipient for oral controlled-release matrix tablet

A polysaccharide mucilage derived from the seeds of fenugreek, Trigonella foenum-graceum L (family Fabaceae) was investigated for use in matrix formulations containing propranolol hydrochloride. Methocel hypomellose K4M was used as a standard controlled release polymer for comparison purposes. In this study the effect of lactose on the release behaviour of propranolol hydrochloride from matrices formulated to contain the fenugreek mucilage also was investigated. An increase in concentration of the mucilage in matrices resulted in a reduction in the release rate of propranolol hydrochloride comparable to that observed with hypomellose matrices. The rate of release of propranolol hydrochloride from fenugreek mucilage matrices was mainly controlled by the drug:mucilage ratio. However, the mechanism of release from matrices containing drug:mucilage ratios of 1:1, 1:1.25, 1:1.5, and 1:2 remained the same. The kinetics of release, utilising the release exponent n, showed that the values of n were between 0.46-0.57 indicating that the release from fenugreek mucilage matrices was predominantly by diffusion. The presence of lactose in matrices containing mucilage increased the release rate of propranolol hydrochloride. This is due to a reduction in tortuoisity and increased pore size of channels caused by lactose through which propranolol diffuses and therefore diffusion of water into the tablet is facilitated.

Developing paediatric medicines: identifying the needs and recognizing the challenges

There is a significant need for research and development into paediatric medicines. Only a small fraction of the drugs marketed and utilized as therapeutic agents in children have been clinically evaluated. The majority of marketed drugs are either not labelled, or inadequately labelled, for use in paediatric patients. The absence of suitable medicines or critical safety and efficacy information poses significant risks to a particularly vulnerable patient population. However, there are many challenges associated with developing medicines for the paediatric population and this review paper is intended to highlight these. The paediatric population is made up of a wide range of individuals of substantially varied physical size, weight and stage of physiological development. Experimentation on children is considered by many to be unethical, resulting in difficulties in obtaining critical safety data. Clinical trials are subject to detailed scrutiny by the various regulatory bodies who have recently recognized the need for pharmaceutical companies to invest in paediatric medicines. The costs associated with paediatric product development could result in poor or negative return on investment and so incentives have been proposed by the EU and US regulatory bodies. Additionally, some commonly used excipients may be unsuitable for use in children; and some dosage forms may be undesirable to the paediatric population.

Influence of ethanol on aspirin release from hypromellose matrices

Release profiles of aspirin from hypromellose matrices in hydro-ethanolic media were studied. Percent aspirin released increased with increasing levels of ethanol in the dissolution media, correlating with the drug's solubility, however, dose dumping of aspirin did not occur. An initial rapid release was observed in media comprising 40% ethanol. Release in these conditions was considered to be both erosion and diffusion-mediated, in contrast to the release in 0, 10, 20 and 30% ethanol media, where erosion-controlled release dominated. Image analysis of matrix swelling indicated a slower initial interaction between ethanol and hypromellose accounting for the initial rapid release. Cloud point studies suggested that ethanol retarded hydration of the polymer.

The killing effect of cryptolepine on Staphylococcus aureus

AIM

This study was undertaken to further examine the antimicrobial actions of the alkaloid cryptolepine.

METHODS AND RESULTS

The minimum inhibitory concentration (MIC) of cryptolepine against Staphylococcus aureus was determined using the broth dilution method. Time-kill kinetics and scanning electron microscopy (SEM) techniques were employed to monitor the survival characteristics and the changes in morphologies respectively of staphylococci in the presence of cryptolepine. A notable antistaphylococcal activity was recorded for cryptolepine (MIC against S. aureus NCTC 10788=5 microg ml(-1)). Cryptolepine appears to have a lytic effect on S. aureus as seen in SEM photomicrographs following 3, 6 or 24 h treatment with 4X MIC, i.e. 20 microg ml(-1) of cryptolepine. The surface morphological appearance of the staphylococcal cells was also altered. The lytic effect appeared to coincide with low viable counts recorded in survival curves following treatment with cryptolepine.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings demonstrate that lysis occurs when susceptible organisms are exposed to cryptolepine.

An assessment of dose-uniformity of samples delivered from paediatric oral droppers

BACKGROUND AND OBJECTIVES

To assess the accuracy and precision of delivery from containers containing oral drops, both under optimal laboratory conditions and during use by volunteers using a variety of real pharmaceutical products and specially prepared fluids.

METHODS

The effects of the physical properties (viscosity, surface tension, fluid density) of fluids and the angle of a dropper upon the accuracy and precision of dispensing were investigated under standard laboratory conditions. Dose delivery was then assessed using a number of volunteers who were either given no instructions on the use of containers or were instructed to hold the droppers vertically.

RESULTS

Viscosity, surface tension, fluid density and residual volume had little or no effect upon the volume of liquid delivered by a dropper clamped in the vertical position. However, when the angle of the dropper was moved towards 45 degrees from the vertical, the volume dispensed declined and became more variable to a point where the requirements of the European Pharmacopoeia were no longer fulfilled. This finding applied to a variety of products. When volunteers used the same droppers manually, the mean volumes dispensed were lower than when the droppers were vertically clamped and the variability was greater. It appeared that these problems were associated with volunteers failing to hold the dropper vertically and the precision and accuracy were indeed increased if the volunteers were instructed as to how the dropper should be held. The results from volunteers were more precise and accurate with the most viscous of the fluids tested and it was speculated that this may have been because the volunteers could more easily use the droppers vertically as there was less fear of dispensing too many drops.

CONCLUSIONS

The key factor in achieving satisfactory dispensing from droppers is to ensure that the dropper is held vertically and this should form the basis of instructions to patients. Formulators should consider increasing the viscosity of prepared dropper solutions to reduce further errors in dose.

The influence of drug type on the release profiles from Surelease-coated pellets

The release of metoclopramide hydrochloride (a water-soluble cationic drug) and diclofenac sodium (a sparingly soluble anionic drug) from pellets coated with ethylcellulose from an aqueous ethylcellulose dispersion (Surelease) at different coating loads was investigated. The release rates of each drug decreased as the coating load of Surelease increased. However, despite its lower water solubility, diclofenac sodium was released slightly faster than metoclopramide hydrochloride at equivalent coating loads. Changes in the release rates after curing were more pronounced for metoclopramide hydrochloride and the release rates of diclofenac sodium were lower than those of metoclopramide hydrochloride after curing. Differences between the release behaviour of the two drugs were probably due to an interaction between the cationic metoclopramide and the anionic ammonium oleate present in the Surelease. The slower release of metoclopramide hydrochloride may be due to an in situ formation of a poorly soluble complex of the drug and the ammonium oleate. This complex, because of its large molecular size, may diffuse more slowly through the film, causing a reduction in the release rate of metoclopramide hydrochloride. This interaction may also account for the differences in release characteristics of the drugs after curing. During curing the surfactant, due to its unstable nature in heat, may be converted to its constituent components. The interaction of drug with the surfactant was reduced as the residue of the ammonium oleate decreased during curing. However, a relatively low volume flow rate of air, and therefore, slower removal of ammonia in the modified side-vented Manesty Accela-cota 10 may also have affected the coating process of the pellets.

Cellularity of human annulus tissue: an investigation into the cellularity of tissue of different pathologies

AIMS

To investigate the cells of the inner annulus and to demonstrate that differences in disc pathology can be identified at the cellular level.

METHODS AND RESULTS

Annulus tissue taken from scoliotic, degenerate and prolapsed human disc tissue was processed for histology and transmission electron microscopy. Ki67 antibody was used to identify cells in the active part of the cell cycle and cell surface receptors for the matrix-degrading enzyme urokinase were immunolocalized. More chondron clusters were observed in tissue from prolapsed discs than in degenerate and scoliotic discs. Positive Ki67 staining was detected in cells within chondron clusters. Most cells observed from scoliotic and prolapsed annulus contained distinctive nuclei and organelles, whereas cells from degenerate discs contained very few well-defined organelles but abundant glycogen deposits. Immunolocalization identified urokinase receptors on the surface of cells from degenerate discs but not in the other pathologies.

CONCLUSIONS

Cellular differences appear to underlie different types of disc pathology. The annulus tissue taken from prolapsed discs appeared to contain more chondron clusters and more active cells than scoliotic and degenerative tissue, suggesting a possible wound repair response. In contrast, cell and matrix degeneration appeared to be the most significant underlying processes in degenerate discs.

Simultaneous determination of ibuprofen and hydroxypropylmethylcellulose (HPMC) using HPLC and evaporative light scattering detection

Ibuprofen may be crystallised in the presence of hydroxypropylmethylcellulose (HPMC) to improve its physical properties. This, however, creates problems with the simultaneous analysis of each ingredient. The analytical method developed utilised high performance liquid chromatography (HPLC) with a stationary phase designed for carbohydrate separation (GylcoSep N) and a mobile phase comprising methanol and water. Evaporative light scattering detection (ELSD) proved a suitable method for the analysis of both HPMC and ibuprofen. Data showed that HPMC and ibuprofen could be quantified in each other's presence. Validation studies indicated that the method was adequately accurate and precise. Baseline resolution was achieved between the two components. HPMC (1.1% w/w) was retained in ibuprofen crystals obtained from alcoholic HPMC suspensions.

Characterisation of water behaviour in cellulose ether polymers using low frequency dielectric spectroscopy

The behaviour of water in hydroxypropylmethylcellulose (HPMC) K100LV, K4M, K15M, K100M, E4M, F4M and HPC polymers was characterised using low frequency dielectric spectroscopy (LFDS). Dielectric responses of 25% (w/w) HPMC K15M gels and deionised water were found to be similar at +22 and 0 degrees C. However, at -30 degrees C, a dielectric response typical of a solid was apparent. The melting of frozen water within gels was detected as increases in the magnitude of the dielectric response with increase in temperature. More than one phase transition was visible in the majority of gels studied which may be related to the presence of different states of water melting at different temperatures. In addition to polymer concentration, both polymer molecular weight and substitution level influenced the nature of the transitions. The magnitude of the dielectric response was increased in all HPMC gel systems in comparison to the response seen in deionised water. Drug addition affected the transitions occurring during the melting of ice in the gels. This may be related to the presence of ionic species in the systems. LFDS studies on cellulose ether gels have provided some interesting evidence for the existence of more than one state of water within such gel systems. The results are in good agreement with thermal analysis findings in similar gel systems.

Structure prediction and active site analysis of the metal binding determinants in gamma -glutamylcysteine synthetase

gamma-Glultamylcysteine synthetase (gamma-GCS) catalyzes the first step in the de novo biosynthesis of glutathione. In trypanosomes, glutathione is conjugated to spermidine to form a unique cofactor termed trypanothione, an essential cofactor for the maintenance of redox balance in the cell. Using extensive similarity searches and sequence motif analysis we detected homology between gamma-GCS and glutamine synthetase (GS), allowing these proteins to be unified into a superfamily of carboxylate-amine/ammonia ligases. The structure of gamma-GCS, which was previously poorly understood, was modeled using the known structure of GS. Two metal-binding sites, each ligated by three conserved active site residues (n1: Glu-55, Glu-93, Glu-100; and n2: Glu-53, Gln-321, and Glu-489), are predicted to form the catalytic center of the active site, where the n1 site is expected to bind free metal and the n2 site to interact with MgATP. To elucidate the roles of the metals and their ligands in catalysis, these six residues were mutated to alanine in the Trypanosoma brucei enzyme. All mutations caused a substantial loss of activity. Most notably, E93A was able to catalyze the l-Glu-dependent ATP hydrolysis but not the peptide bond ligation, suggesting that the n1 metal plays an important role in positioning l-Glu for the reaction chemistry. The apparent K(m) values for ATP were increased for both the E489A and Q321A mutant enzymes, consistent with a role for the n2 metal in ATP binding and phosphoryl transfer. Furthermore, the apparent K(d) values for activation of E489A and Q321A by free Mg(2+) increased. Finally, substitution of Mn(2+) for Mg(2+) in the reaction rescued the catalytic deficits caused by both mutations, demonstrating that the nature of the metal ligands plays an important role in metal specificity.

Effect of compression force, compression speed, and particle size on the compression properties of paracetamol

The compression characteristics of two particle size fractions (< 90 microm, 105-210 microm) of paracetamol were examined. Each fraction produced extremely weak tablets and displayed a high tendency to cap. Low correlation coefficients of the initial parts of the Heckel plots, a low strain rate sensitivity, and an increase in mean yield pressure (from 34.2 to 45.5 MPa) with decrease in particle size all confirmed that the main mechanism during the compaction of paracetamol was fragmentation. The 105-210-microm particles underwent more fragmentation than the less than 90-microm powder. Heckel analysis confirmed that the larger size fraction of paracetamol produced denser compacts than the smaller fraction. The 105-210-microm fraction resulted in tablets with lower elastic recoveries and elastic energies. The elastic, plastic energy ratios indicated that the majority of energy involved during the compaction of paracetamol was utilized as elastic energy, indicative of massive elastic deformation of paracetamol particles under pressure.

Effect of nicotinamide on the properties of aqueous HPMC solutions

The effect of nicotinamide on the properties of aqueous hydroxypropylmethylcellulose (HPMC) solutions was studied. Rheological studies showed that solutions of HPMC of concentration less than 3.0 w/v.% did not form gels and exhibited Newtonian flow patterns at 25 degrees C. The inclusion of nicotinamide increased the viscosity of HPMC solutions, which indicates that nicotinamide expanded the HPMC coils in aqueous solution. When the temperature of the solutions was raised, they formed gels that were detected by viscometry and oscillation tests as abrupt increases in viscosity, storage modulus and loss modulus and an abrupt decrease in loss angle. Nicotinamide exhibited a salting in effect on the HPMC solutions resulting in an increase in gelation temperatures and cloud points. These effects are considered to be due to the hydrogen-bonding of nicotinamide to HPMC molecules, which was suggested by a shift to a longer wavelength of the UV spectra of aqueous nicotinamide solutions by the addition of HPMC. These results suggested that nicotinamide has affinity with the hydrophilic groups of HPMC.

Characterization of the hydroxypropylmethylcellulose-nicotinamide binary system

The effect of hydroxypropylmethylcellulose (HPMC) on the thermal behaviour of nicotinamide was studied. Binary mixtures of nicotinamide and HPMC, composed of various weight fractions of HPMC (X(HPMC)), were heated, cooled and subsequently re-heated. HPMC dissolved in fused nicotinamide at 140 degrees C. The binary mixture at compositions 0<==X(HPMC)<==0.3 formed a film structure on cooling. At X(HPMC)>==0.4, the molten nicotinamide at 140 degrees C was saturated with HPMC. These heated mixtures did not form a homogeneous film by cooling to ambient temperature. At X(HPMC)<0.4, differential scanning calorimetry peaks originating from recrystallization and melting of nicotinamide were observed in the cooling and re-heating scans, respectively. These peaks became smaller with increase in X(HPMC) and disappeared at X(HPMC) approximately 0.4. Decrease in crystallinity with increase in X(HPMC) was confirmed by X-ray diffraction. The glass transition temperature of the cooled mixture (T(g)) increased with increase in X(HPMC). When the enthalpy of melting of nicotinamide and 1/T(g) were plotted against X(HPMC), inflections were observed at similar X(HPMC) values, 0.37-0.38. Dissolution of HPMC in molten nicotinamide was accompanied by hydrogen bond formation, which was confirmed by infrared studies.

Study of drug release from pellets coated with Surelease containing hydroxypropylmethylcellulose

The release of metoclopramide hydrochloride (a very water soluble cationic drug) and diclofenac sodium (a sparingly soluble anionic drug) from pellets coated with Surelease containing hydroxypropylmethylcellulose (HPMC) at different coating loads was investigated. The release rates of either drug at each coating composition decreased as the coating load increased. Inclusion of HPMC E15 increased the release rates of both drugs compared to pellets coated only with Surelease. This was thought to be due to the leakage of the soluble part of the film (HPMC E15) during dissolution, which left pores for drug release. The Surelease:HPMC E15 ratio had a major role in the release rates of drugs. Addition of HPMC E15 into Surelease did not change the release mechanism for metoclopramide hydrochloride (the mean value of n approximately 0.57) from that of Surelease alone, and diffusion remained the main mechanism controlling the release. However, the release exponent (approximately 1.28) increased for diclofenac sodium on addition of HPMC E15, indicating a dissolution-controlled mechanism. Despite its lower water solubility, diclofenac sodium was released slightly faster than metoclopramide hydrochloride from pellets coated with Surelease containing HPMC E15 at equivalent coating loads.

Highly compressible paracetamol: I: crystallization and characterization

It was found that polyvinylpyrrolidone (PVP) is an effective additive during crystallization of paracetamol and significantly influenced the crystallization and crystal habit of paracetamol. These effects were attributed to adsorption of PVP onto the surfaces of growing crystals. It was found that the higher molecular weights of PVP (PVP 10000 and PVP 50000) were more effective additives than lower molecular weight PVP (PVP 2000). Paracetamol particles obtained in the presence of 0.5% w/v of PVP 10000 or PVP 50000 had near spherical structure and consisted of numerous rod-shaped microcrystals which had agglomerated together. Particles obtained in the presence of PVP 2000 consisted of fewer microcrystals. Differential scanning calorimetry (DSC) and X-ray powder diffraction (XPD) experiments showed that paracetamol particles, crystallized in the presence of PVP, did not undergo structural modifications. By increasing the molecular weight and/or the concentration of PVP in the crystallization medium the amount of PVP incorporated into the paracetamol particles increased. The maximum amount of PVP in the particles was 4.32% w/w.

Highly compressible paracetamol - II. Compression properties

Paracetamol particles crystallized in the presence of polyvinylpyrrolidone (PVP) exhibited an obvious improvement in their compression properties compared to untreated paracetamol. Paracetamol particles crystallized in the presence of 0.5% w/v PVP 10000 or PVP 50000 produced tablets with improved crushing strength with no tendency to cap even at high compression speeds. The very low values of strain rate sensitivity (SRS) and the lack of reduction in crushing strength with increasing compression speed for these particles, were indicative of a high degree of fragmentation during compression. The results of elastic recoveries and elastic energies of tablets were indicative of much less elastic behaviour of these particles than untreated paracetamol. The low elastic energy/plastic energy (EE/PE) ratio for paracetamol crystallized in the presence of PVP indicated that, contrary to untreated paracetamol, a minor portion of compression energy was utilized as elastic energy.