Variability in free 25(OH) vitamin D levels in clinical populations

Our goal was to determine total and directly measured free 25-hydroxy vitamin D (25(OH)D) serum levels in humans with a range of 25(OH)D levels and clinical conditions associated with low and high vitamin D binding protein levels. Serum samples and clinical data were collected from 106 subjects: 62 without cirrhosis or pregnancy, 24 cirrhotic patients with albumin <2.9g/dL, and 20 pregnant women. Total 25(OH)D (LC/MS/MS) and "free" 25(OH)D (immunoassay) were measured. Total 25(OH)D was significantly lower in liver disease patients but free 25(OH)D concentrations were significantly higher in this group (p<.001). Neither total nor free 25(OH)D concentrations were significantly different in pregnant women vs. the comparator group. There were significant direct positive relationships between free 25(OH)D and total 25(OH)D concentrations for the entire dataset and for each group (p<.0001), however slopes of relationships differed in the cirrhotic group compared to pregnant women or the comparator group. In cirrhotics: y (free 25(OH)D)=2.52+0.29×X(total 25 (OH)D), r(2)=.51, p<.001; y=1.45+0.09×X; r(2)=.77, p<.0001 for pregnant women; and y=1.11+0.12×X; r(2)=.72, p<.0001 for the comparator group).

CONCLUSIONS

directly measured free 25(OH)D serum concentrations and relationships between total and free 25(OH)D vary with clinical conditions, and may differ from those predicted by indirect estimation methods. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

A comparison of measured and calculated free 25(OH) vitamin D levels in clinical populations

OBJECTIVE

Our goal was to compare direct quantitation of circulating free 25-hydroxyvitamin D (25(OH)D)levels to calculated free 25(OH)D levels and their relationships to intact PTH (iPTH), a biomarker of 25(OH)D effect, in humans with a range of clinical conditions.

PATIENTS AND METHODS

Serum samples and clinical data were collected from 155 people: 111 without cirrhosis or pregnancy (comparison group), 24 cirrhotic patients with albumin <2.9 g/dL, and 20 pregnant women (second and third trimester). Total 25(OH)D (LC/MS/MS), free 25(OH)D (immunoassay), vitamin D binding protein (DBP) (immunoassay), albumin, and iPTH (immunoassay) were measured.

RESULTS

Total 25(OH)D, DBP, and albumin were lowest in patients with cirrhosis, but measured free 25(OH)D was highest in this group (P < .001). DBP was highest in pregnant women (P < .001), but measured free 25(OH)D did not differ from the comparison group. Calculated free 25(OH)D was positively correlated with measured free 25(OH)D (P < .0001) but explained only 13% of the variability with calculated values higher than measured. African Americans had lower DBP than other ethnic populations within all clinical groups (P < .03), and differences between measured and calculated free 25(OH)D were greatest in African Americans (P < .001). Measured free 25(OH)D was correlated with total 25(OH)D (P < .0001; r(2) = 0.51), but calculated free 25(OH)D was not. Similarly, both measured free 25(OH)D (P < .02) and total 25(OH)D (P < .05) were correlated with iPTH, but calculated free 25(OH)D was not.

CONCLUSIONS

Calculated free 25(OH)D levels varied considerably from direct measurements of free 25(OH)D with discrepancies greatest in the data for African Americans. Differences in DBP binding affinity likely contributed to estimation errors between the races. Directly measured free 25(OH)D concentrations were related to iPTH, but calculated estimates were not. Current algorithms to calculate free 25(OH)D may not be accurate. Further evaluation of directly measured free 25(OH)D levels to determine its role in research and clinical management of patients is needed.

Patterns of chronic co-morbid medical conditions in older residents of U.S. nursing homes: differences between the sexes and across the agespan

OBJECTIVE

There are limited data on combinations of co-morbid conditions to guide efforts to improve therapeutic strategies in patients with multiple co-morbid conditions. To some extent, this may be due to limited data on combinations of co-morbid conditions in patient groups. Our goal was to determine the most common co-morbid medical conditions in older residents of U.S. nursing homes and identify sex differences in prevalences and changes across the agespan of nursing residents.

DESIGN

Cross sectional analysis of National Nursing Home Survey (NNHS)--a nationally representative sample with comprehensive medical data on nursing home residents.

SETTING

1174 Nursing homes.

PARTICIPANTS

Long term stay residents of U.S. Nursing Homes aged 65 years and older (11,734 :8745 women, 2989 men).

MEASUREMENTS

Determination of the prevalences of the most frequent two and three disease combinations identified using Clinical Classifications Software (CCS) for ICD-9-CM and a composite vascular disease diagnosis (atherosclerosis and/or coronary artery disease, and/or peripheral arterial disease, and/or cerebrovascular disease or stroke) from the most recent and only NNHS survey with comprehensive medical diagnosis information.

RESULTS

Frequent 2-disease combinations were: hypertension (HTN) + dementia (DEM) in 27%, HTN + any Vascular (Vasc) disease (26%), HTN + depression(DEP) 21%, HTN + arthritis(ARTH) 20%, DEM + Vasc (21%), DEM+Depression 19%, Arthritis + DEM 17%, DEP + Vasc (16%), ARTH + Vasc (15%), followed by HTN + GERD (14%) and ARTH + DEP (14%). Frequent 3-disease combinations: HTN +VASC+ DEP in 13%, HTN +DEM +DEP (11%), and HTN+Arthritis+DEM (10%). HTN was in 80% of the top 3-disease combinations, Vasc in 50%, HTN+VASC in 35%, DEM or DEP in 40%, ARTH in 25% and GERD in 20%. Combinations with anemia, arthritis, dementia, heart failure, osteroporosis, thyroid disease were higher in women, COPD combinations higher in men. As age increased, dementia, depression, arthritis, and anemia with hypertension were common co-morbid combinations, diabetes and heart failure were not.

CONCLUSIONS

Hypertension, vascular disease, dementia, arthritis, depression, and gastro-esophageal reflux disease were part of the most prevalent co-morbid conditions. Multimorbidity patterns can be identified in nursing home residents and vary with age and by sex.

Association of CYP2C9*2 with bosentan-induced liver injury

Bosentan (Tracleer) is an endothelin receptor antagonist prescribed for the treatment of pulmonary arterial hypertension (PAH). Its use is limited by drug-induced liver injury (DILI). To identify genetic markers of DILI, association analyses were performed on 56 Caucasian PAH patients receiving bosentan. Twelve functional polymorphisms in five genes (ABCB11, ABCC2, CYP2C9, SLCO1B1, and SLCO1B3) implicated in bosentan pharmacokinetics were tested for associations with alanine aminotransferase (ALT), aspartate aminotransferase (AST), and DILI. After adjusting for body mass index, CYP2C9*2 was the only polymorphism associated with ALT, AST, and DILI (β = 2.16, P = 0.024; β = 1.92, P = 0.016; odds ratio 95% CI = 2.29-∞, P = 0.003, respectively). Bosentan metabolism by CYP2C9*2 in vitro was significantly reduced compared with CYP2C9*1 and was comparable to that by CYP2C9*3. These results suggest that CYP2C9*2 is a potential genetic marker for prediction of bosentan-induced liver injury and warrants investigation for the optimization of bosentan treatment.

Lenalidomide enhancement of human T cell functions in human immunodeficiency virus (HIV)-infected and HIV-negative CD4 T lymphocytopenic patients

Suppressed T cell functions in human immunodeficiency virus (HIV) infection were identified and corrected by lenalidomide in middle-aged HIV-infected patients. Chemotaxis of T cells from HIV-infected men (n = 6, mean 43 years) to sphingosine 1-phosphate (S1P) and CCL21 was significantly lower than that of HIV-negative men (n = 6, mean 41 years), and was enhanced significantly up to control levels by 100 and 1000 nM lenalidomide. Generation of interleukin (IL)-2, but not interferon (IFN)-γ, by T cells of middle-aged HIV-infected men was significantly lower than that for controls and was increased significantly by 10-1000 nM lenalidomide up to a maximum of more than 300%. CD4 and CD8 T cells isolated from healthy middle-aged men and reconstituted in vitro at a low CD4 : CD8 ratio typical of HIV infection had depressed chemotaxis to S1P, but not CCL21, and generation of IL-2, but not IFN-γ. Significant enhancement of chemotaxis to S1P and CCL21 was induced by 100-1000 nM lenalidomide only for normal T cells at a low CD4 : CD8 ratio. T cells from HIV-negative middle-aged CD4 T lymphocytopenic patients (n = 3), with a CD4 : CD8 ratio as low as that of HIV-infected patients, had similarly diminished chemotaxis to S1P and CCL21, and depressed generation of IL-2, but not IFN-γ. Lenalidomide at 30-1000 nM significantly enhanced chemotaxis to S1P and IL-2 generation for T cells from HIV-negative CD4 T lymphocytopenic patients as from HIV-infected patients, with less effect on CCL21-elicited chemotaxis and none for IFN-γ generation. Defects in functions of T cells from middle-aged HIV-infected men are partially attributable to CD4 T lymphocytopenia and are corrected by lenalidomide.

Effects of testosterone on the Q-T interval in older men and older women with chronic heart failure

The Q-Tc interval duration on the electrocardiogram is recognized to differ between the sexes. In vitro data and data from humans before and after puberty and menopause suggest that sex hormones play a role in the longer Q-Tc intervals in women, or conversely, the shorter Q-Tc intervals in men. Direct investigations of sex hormone effects on the Q-Tc interval in humans, however, are limited and reach conflicting conclusions. Our objective was to determine effects of testosterone on ECG Q-T intervals of older men and older women. ECG's from 84 older men and older women in double-blind placebo-controlled investigations of testosterone supplementation for the treatment of chronic heart failure (CHF) were analysed. Thirty men received 1000mg intramuscular long-acting testosterone undecanoate and 28 men received saline at 0, 6 and 12weeks. ECG's were recorded at baseline and 12weeks. Sixteen women received transdermal testosterone (33μg) and 10 women received matching placebo twice weekly for 24 weeks with ECG's at baseline and after 24weeks. Testosterone, but not placebo, shortened Q-T and Q-Tc intervals without heart rate changes. Q-T intervals decreased from 385±28 (mean±SD) to 382±28 ms (p<0.002) and Q-Tc intervals decreased from 398±26 to 392±27 (p<0.006) in men on testosterone. In women, Q-T intervals decreased from 400±25 to 397±23ms (p=0.06) and Q-Tc intervals from 415±26 to 409±27ms (p=0.3) on testosterone. Q-T intervals were longer in women compared with men under all conditions (p<0.03). The data support a direct effect of testosterone to shorten Q-T intervals in older men and older women in the absence of HR changes or hypogonadal status. Mean decreases are small and unlikely to affect risks of arrhythmic events in patients receiving Q-T prolonging medications.

The Effect of Wax on Compaction of Microcrystalline Cellulose Beads Made by Extrusion and Spheronization

The effect of wax on the deformation behavior and compression characteristics of microcrystalline cellulose (Avicel PH-101) and acetaminophen (APAP) beads is described. Beads of Avicel PH-101 and APAP formulations were prepared using extrusion and spheronization technology. A waxy material, glyceryl behenate, N.F. (Compritol), was added to the formulations in amounts ranging from 10% to 70% of total solid weight. Beads with a selected particle size range of 16-30 mesh were compressed with an instrumented single punch Manesty F press utilizing a 7/16-in. flat-faced tooling set. Compaction profiles were generated for the tablets to evaluate the effect of wax on the densification of beads containing wax. Beads made without wax (the control formulation) required greater compression forces to form cohesive tablets. As the amount of wax in the bead formulation was increased, the beads become more plastic and compressible. The Heckel equation which relates densification to compression pressure was used to evaluate the deformation mechanisms of the bead formulations. The analysis shows that as the level of wax in the bead formulation is increased, the yield pressure decreases, indicating that the beads densify by a plastic deformation mechanism.

Protective effect of Carbopol on enzymatic degradation of a peptide-like substrate. I: Effect of various concentrations and grades of Carbopol and other reaction variables on trypsin activity

The purpose of this study was to determine and compare the effect of various concentrations and grades of Carbopol on trypsin-induced degradation of a prototype substrate, N(alpha)-benzoyl-L-arginine ethyl ester hydrochloride (BAEE). Effect of other reaction variables, such as viscosity and ionic strength of the medium on the trypsin activity, was also analyzed simultaneously. Four concentrations and three commercially available grades of Carbopol were used. The effect of Carbopol was expressed in terms of change in the velocity of degradation reaction. A modified trypsin assay was developed and used for analysis. Up to a concentration of 0.35% w/v, Carbopol 934P showed a concentration-dependent increase in its ability to reduce the rate of enzymatic hydrolysis of BAEE. Similar inhibitory effect was observed with all three grades of Carbopol. The activity of trypsin was unaffected by other reaction variables, suggesting that interaction between the protein and the polymer could be the mechanism responsible for reduced trypsin activity. This study suggests that Carbopol can be a useful excipient for oral delivery of bioactive proteins and peptides, due to its ability to reduce the enzyme-induced degradation of these agents.

The Current State of Knowledge on Age, Sex, and Their Interactions on Clinical Pharmacology

Pharmacokinetic and pharmacodynamic changes occur with increasing age. Sex differences in pharmacokinetics and pharmacodynamics exist and persist at older age. The issue for the clinician is how to best treat the older patient with currently available knowledge. This communication highlights age- and sex-related differences in pharmacokinetics that should influence clinical practice and prescribing guidelines to optimize clinical responses. The most compelling data for sex-specific medication dosing guidelines for older patients are related to volume of distribution differences, or size differences, between the sexes and to differences in glomerular filtration rates.

The evaluation of pharmacologic therapy in humans: a brief summary of the drug evaluation process and guidelines for clinical trials as they related to women

Significant progress has been made in including women in clinical and drug evaluation trials. Nonetheless, for most drugs currently on the market, analysis of benefits by sex is not available. At least some of the adverse effects of newer drugs in women could be due to the lack of inclusion in studies from which therapeutic regimens were derived. The data currently available on potential sex differences in pharmacokinetics and pharmacodynamics are also limited by having been obtained from healthy subjects receiving only one medication in studies designed only to detect moderate-to-large (> 30-50%) differences between the sexes. The clinical environment is different: patients consume multiple medications, including over-the-counter medications as well as nutraceuticals and dietary supplements; patients are, on average, older than healthy volunteers or even patients enrolled in investigational studies; and patients are more likely to have multiple diseases. In addition, adequate numbers of women still have not been enrolled in clinical trials for the therapy of many common disorders. The prudent clinician will remember that every time a therapy is initiated for an individual patient, especially a female patient, it is a clinical trial and the outcome is uncertain.

Effect of processing methods and heat treatment on the formation of wax matrix tablets for sustained drug release

The objective of this study was to evaluate the effects of processing methods and heat treatment on matrix formation and subsequent drug release from wax matrix tablets for controlled release. Phenylpropanolamine hydrochloride (PPA) and Compritol were processed with appropriate diluent(s) using either dry blending (DB), wet granulation (WG), partial melt granulation (PMG), or melt granulation (MG). Then the tablets were heat-treated at 80 degrees C. Particle size distribution and compressibility, along with drug release, tablet micro-morphology, wettability, porosity, and tortuosity were investigated. The drug release was different for the four processing methods even though the tablet formulation was identical. Heat treatment further retarded drug release and its effect was related to the previous manufacturing processes. Scanning Electron Microscopy (SEM) showed that heat treatment redistributed the wax and formed a film-like structure covering drug and excipients. The contact angle of tablets made from DB, WG, and PMG methods increased after heat treatment, while that of tablets made from MG remained constant. Tablet tortuosity calculated from drug release rate constants increased dramatically after heat treatment. Drug release from the wax tablets with or without heat treatment was best described by the Higuchi equation. Different processing methods produced different matrix structures that resulted in different drug release rates. Heat treatment retarded drug release mainly by increasing tortuosity of the matrix. Contact angle measurement and SEM analysis indicated that heat treatment caused the wax to melt, redistribute, coat the drug and diluents, and form a network structure.

The effect of formulation composition and dissolution parameters on the gel strength of controlled release hydrogel tablets

The impact of hydrogel polymers and dissolution media on tablet gel strength, Gamma, of controlled release (CR) hydrogel tablets was investigated. CR tablets containing either hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), or carbomer were formulated with theophylline and Fast Flo lactose, to produce tablets with a polymer content of 8, 15, and 30% w/w. Gamma was measured using a previously reported method. The drug dissolution profiles were similar, irrespective of polymer type or dissolution media (DI water, 0.1 N HCl, and pH 6.8 phosphate buffer), at the same % w/w level of polymer. Gamma, however, showed large and significant differences (p < or = 0.05) between tablets containing different polymers and between different dissolution media. Gamma values were HPMC KI00MP > HPC HXF > carbomer 971P (same % w/w) with absolute Gamma values at 30% w/w in DI water of 6600, 4600, and 1600 ergs/cm3, respectively. Gamma for HPMC based tablets was independent of changes in dissolution media, while the Gamma values for HPC tablets were 18% lower in acid and buffer than in DI water. Of the polymers tested, carbomer based tablets had the lowest Gamma values in all dissolution media and an unexpected 58% lower Gamma in buffer compared with DI water or acid. Gamma provides a quantitative measure of the effect of formulation and dissolution parameter changes on tablet gel layer strength, under in vitro stress conditions that may parallel in vivo tablet performance, but which cannot be deduced from a comparison of dissolution profiles or polymer viscosity.

The effects of formulation factors on the moist granulation technique for controlled-release tablets

Controlled-release tablets were prepared by the moist granulation technique (MGT), a granulating method that uses very limited amounts of liquid and requires microcrystalline cellulose (MCC) to absorb moisture. Acetaminophen (APAP) was the model drug, and the polymer hydroxypropylcellulose (HPC) served as the controlled-release agent. The effects of varying drug, binder (polyvinylpyrrolidone, PVP), polymer, and MCC levels on granule properties and tablet dissolution were studied. Dissolution testing was carried out in distilled water using the USP paddle method. In all cases, the granules flowed and compressed well. The granule properties were evaluated by calculating the mean particle size for all batches from sieve analysis data. The results indicate that MGT can be applied to control drug release, and at a polymer content of 44.6% or more, the process is robust enough to allow slight variations in formulation factors without affecting drug release.

Antimicrobial and diffusional correlation of N-alkyl betaines and N-alkyl-N,N-dimethylamine oxides from semisolids

Previous studies have shown that two classes of amphoteric surfactants, N-alkyl betaines and N-alkyl-N,N-dimethylamine oxides, exhibit pronounced antimicrobial activity in combination and have potential for use in a semisolid formulation for topical or vaginal delivery. In this work, several potential delivery systems were prepared and evaluated for antimicrobial activity and diffusional properties. A novel antimicrobial test for semisolids was proposed that determined the contact time needed to kill microorganisms. The unformulated agents in solution exhibited the faster kill within 60 min, followed by the hydroxyethylcellulose gel formulation in 90 min, and the poloxamer gel and a cream that required several hours. Diffusion from the dosage form utilized a Slide-A-Lyzer diffusion cassette with a 10,000 MWCO membrane with (14)C-labeled active species added to the aforementioned antimicrobial formulations. Diffusion of the individual betaine and amine oxide derivatives were tracked over time to determine the diffusion rates and profiles of the components in each formulation and in solution. The betaine derivative diffused up to three times faster than the amine oxide derivative within the first 2 h, but the amount diffused was approximately equivalent at 24 h. The formulations delayed release in the same rank order as the contact time kill analysis: hydroxyethylcellulose gel > poloxamer gel > cream.

A novel method for measuring gel strength of controlled release hydrogel tablets using a cone/plate rheometer

A novel method for measuring gel strength of hydrogel controlled release (CR) tablets is presented. CR tablets containing hydroxypropyl methylcellulose (HPMC) were fixed to a glass plate, placed in a dissolution apparatus, and subjected to dissolution conditions corresponding to 50% drug release. Tablets were then removed from the dissolution apparatus without disturbing the swollen (gel) layer. Tablet gel strength (gamma) was determined by shearing the external gelled layer of the tablet by a cone/plate rheometer recording E, energy/volume, as a function of rotational speed of the cone, RPM. The RPM is increased to the point of "Shear Failure," RPMsf, i.e., until there is no further increase in E. Plots of E vs. RPM were fit to a bi-exponential equation, where epsilon is the zero RPM intercept of the plot. gamma is calculated from gamma = ERPMsf - epsilon. gamma is defined as the minimum energy input/unit volume needed to cause shear failure of the tablet gel layer. Mean gamma for tablets containing 50% theophylline and different ratios of HPMC to Fast Flo lactose were determined. Tablets containing 30%, 15%, and 8% HPMC K100MP have gamma means of 6600, 4700, and 1500 ergs/cm3, and percent relative standard deviations of 9, 13, 33%, respectively. Tablets made entirely of HPMC K100MP (no theophylline or lactose) have an gamma of 15,500 ergs/cm3. gamma values are significantly different (p < 0.0001) between the various formulations. gamma values also show a strong inverse correlation with the cumulative percent of drug released in vitro. Results obtained demonstrate the application of this novel method for measuring gel strength of different CR hydrogel tablets and using this strength to characterize drug diffusion in vitro.

Use of a moist granulation technique (MGT) to develop controlled-release dosage forms of acetaminophen

The moist granulation technique (MGT), which involves agglomeration and moisture absorption, has only been applied to immediate-release dosage forms. Our results indicate that MGT appears to be applicable in developing a controlled-release formulation. A small amount of granulating fluid (water) was added to a powder blend to activate a dry binder (such as polyvinylpyrrolidone [PVP] at 2% and 3.6%) and to facilitate agglomeration. Then, a moisture-absorbing material (microcrystalline cellulose [MCC]) was added to absorb any excess moisture. By adding MCC in this way, a drying step was not necessary. Acetaminophen (APAP) was the model drug, with diluents lactose FastFlo and dicalcium phosphate. Hydroxypropylcellulose (HPC) was used as the controlled-release agent. The MGT was compared to conventional wet granulation (WG) and direct compression (DC) processing methods. The results indicate that MGT appears to be applicable in developing a controlled-release formulation. Particle size distribution of MGT and WG batches containing 3.6% PVP is similar.

Race but not age affects erythromycin breath test results in older hypertensive men

Erythromycin breath tests (ERBT) were performed to determine age and racial effects on CYP3A4-mediated hepatic clearance in hypertensive men (n = 43) in the clinical setting. Older hypertensive African American men (n = 19: 71 +/- 8 years, mean +/- SD) had faster ERBT clearance compared with Caucasian (n = 20: 72 +/- 6 years) hypertensive men (at 20 minutes after dosing: 0.042 +/- 0.01 percent dose/min exhaled vs. 0.033 +/- 0.013; at 60 minutes after dosing: 0.030 +/- 0.05 vs. 0.023 +/- 0.007 percent dose/min exhaled; ANOVA, p = 0.007), while age, smoking, and reported alcohol intake did not affect ERBT. The data suggest faster hepatic CYP3A-mediated clearance in African American men compared with Caucasian men, and that race may significantly affect CYP3A-mediated hepatic clearance in patients treated for hypertension.

Drug release from film-coated chlorpheniramine maleate nonpareil beads: effect of water-soluble polymer, coating level, and soluble core material

The purpose of this research was to use a new drug release model to study the effects of formulation parameters on drug release from a film-coated chlorpheniramine (CPM) nonpareil system. The film-coated CPM nonpareils were prepared by using a fluid bed apparatus. A hydroxylpropylmethylcellulose (HPMC) solution was blended with an aqueous ethylcellulose dispersion (Surelease) to adjust the permeability of the film. The apparent permeability of samples was obtained from dissolution data using a previously reported drug release equation. The apparent permeability was plotted versus the film coating level or the HPMC concentration in the film. When the natural logarithm of the apparent permeability versus coating level was graphed, a biphasic plot was observed in the group without HPMC in the film, showing the occurrence of a critical coating level. It was suggested that a mechanically formed porous film (due to an incomplete coating) could change to a nonporous film after the bead was completely coated. However, in the group that contained 12% HPMC in the film, the critical coating level was not observed. A porous film, formed by the leaching out of the water-soluble polymer, would not change to a nonporous film even after the bead is completely coated. Through a mathematical derivation, the decrease of apparent permeability versus coating level was related to the reduction of the total hole area. The apparent permeability was found to increase with the HPMC concentration. After a critical concentration was reached, the further addition of HPMC into the film caused a rapid increase in apparent permeability. The critical HPMC concentration was related to a minimum domain formation concentration (MDFC). A rapid increase of the drug release was observed when the dissolution profile of a sample made from a regular sugar nonpareil core (soluble) was compared with the sample made from a precoated nonpareil core (insoluble), which suggests that the drug release can be enhanced by the dissolution of the core. A minimum concentration of the HPMC was required to effectively modify permeability of the film. The critical coating level and critical concentration of HPMC can be determined from the apparent permeability plot using a previously published equation. The dissolution of a soluble core can greatly enhance the release of the drug from the nonpareil system.

Thermodynamic analysis of compact formation; compaction, unloading, and ejection. II. Mechanical energy (work) and thermal energy (heat) determinations of compact unloading and ejection

A compaction calorimeter, previously described (DeCrosta, M.T., Schwartz, J.B., Wigent, J.B., Marshall, K., 2000. Thermodynamic analysis of compact formation; compaction, unloading, and ejection. I. Design and development of a compaction calorimeter and mechanical and thermal energy determinations of powder compaction. Int. J. Pharm. 198, 113--134), was utilized to evaluate the thermodynamics of the unloading and ejection of compacts of Avicel pH102, Emcompress, Fast-Flo #316, Starch 1500, and acetaminophen (APAP). A constant strain waveform, applied by a compaction simulator, enabled the separate thermodynamic evaluation of unloading from compaction. The brittle materials, Fast-Flo #316 and Emcompress, displayed the most unloading work, and the plastic/self-lubricating materials, Avicel and Starch 1500, displayed the least. Unloading heat values were negative for all materials, except APAP. APAP's positive heat values indicated the breaking of bonds during unloading as a result of its highly elastic nature. Positive internal energy changes of unloading, which indicate the net breaking of bonds, were observed for APAP and Emcompress over the compaction forces tested. Negative energy changes for Starch 1500, Fast-Flo #316, and Avicel became positive with increasing compaction forces. Ejection work increased with increasing compaction force for the brittle materials, whereas smaller ejection work values for Avicel, Starch 1500, and APAP remained constant. Increasing negative heat values as a function of compaction force were observed for Fast-Flo #316 and Emcompress. Negative internal energy values for ejection were observed for Fast-Flo #316 and Emcompress, which indicates net bond formation as a result of high shear of the compact with the die wall. Internal energy changes for Starch 1500, Avicel, and APAP, were approximately zero, indicating the absence of net bonding or bond formation during the process.

Effects of age and gender on the QT response to exercise

Although gender differences in resting corrected QT intervals have been well documented, the effects of age and exercise on gender differences in QT have not been well characterized. Data were analyzed from 91 healthy volunteers (47 women). Forty-five young subjects (aged 20 to 39 years) and 46 older subjects (61 to 84 years) were recruited. All underwent Bruce protocol stress testing. QT offset and QT peak were measured at exercise stages and during recovery. In a heart rate (HR)-independent analysis, data were divided into HR bins of 10 beats/min. In a HR-dependent analysis, 6 models were used to approximate the QT-RR relation; the best were used to analyze age and gender effects. Women had longer QT intervals than men at a HR < 100 beats/min for QT offset and < 110 beats/min for QT peak. At faster HRs, no significant differences were found. Older subjects had slightly longer QT intervals than the younger group, with a mean difference of 2 ms for QT offset and 9 ms for QT peak. Women had increased constant and slope coefficients. The QT increase in the elderly was relatively small. Gender differences in QT disappear at faster HRs, whereas age differences are smaller but are present throughout exercise, with no significant age-gender interaction. A natural logarithmic model provides the best approximation of the QT-RR relation with exercise, is simple to implement, and should become the preferred method of QT correction.

Vitamin intake, recommended intake, and gender differences

The role of vitamins in promoting good health and preventing disease is currently gaining recognition. Daily iron and folate intake should be higher in menstruating women than in men of similar age, while lower total intake of vitamins A, B, E, K, and zinc are based on body size, and recommendations are usually lower in women compared to men. Adequate daily intake can be achieved through a balanced diet for most nutrients and vitamins. Exceptions are the need for supplementation of most vitamins and folate in pregnant women and for vitamin D and calcium in older individuals.

Diffuse idiopathic skeletal hyperostosis causes artificially elevated lumbar bone mineral density measured by dual X-ray absorptiometry

A 76-yr-old man with bilateral total hip arthroplasties was referred for a baseline bone mineral density (BMD) measurement. The L1-L4 lumbar bone density revealed a density above the upper expected value for a young individual (i.e., T-score > 2.5) with large intervertebral variation, while the forearm study revealed an osteoporotic measurement. Lumbar spine radiographs demonstrated abundant, flowing ossification of the anterior spinal ligament, predominantly at L3, consistent with diffuse idiopathic skeletal hyperostosis, which accounted for the increased BMD.

Congestive heart failure medications: is there a rationale for sex-specific therapy?

The etiology and physiology of symptomatic heart failure may differ by sex. Prognostic markers for outcomes of CHF may also have sex-specific sensitivity. Insufficient numbers of women have been enrolled in most large interventional survival studies of pharmacologic therapy for CHF to test for sex-specific efficacy or responses. There are some data that demonstrate sex-specific lack of efficacy and increase in side effects of therapy. Given that the number of women admitted to hospitals with CHF each year exceeds the number of men, there is an obvious need to specifically and definitively evaluate the pharmacologic therapy of CHF in women.

Faster clearance of sustained release verapamil in men versus women: continuing observations on sex-specific differences after oral administration of verapamil

Pharmacokinetic studies after administration of 120 mg oral sustained- and regular-release racemic verapamil were performed in 13 healthy subjects (seven men, age 74 +/- 4 years [mean +/- SD], weight 69.9 +/- 5.4 kg, and body mass index 24.6 +/- 2.2]; and six women, age 65 +/- 13 years, weight 65 +/- 9.9 kg, and body mass index 25.3 +/- 3). Verapamil was measured by HPLC, concentration versus time data analyzed by noncompartmental models, and statistical analyses performed by ANOVA for repeated measurements. The area under the concentration versus time curve (AUC) after administration of sustained-release verapamil was 48,951 +/- 18,079 ng/mL x min(-1) in women compared with 25,595 +/- 10,245 in men and lower than after administration of regular-release verapamil (63,055 +/- 24,411 for women and 34,686 +/- 25,279 in men; P = .05 for sex-related effect and P < .02 for formulation effect). AUC ratios of norverapamil (N-demethylated metabolite) to verapamil after administration of sustained-release verapamil were 1.43 +/- 0.26 in women compared with 1.74 +/- 0.41 in men and 1.43 +/- 0.26 in women compared with 1.78 +/- 0.37 in men after administration of regular-release verapamil (P = .1 for sex-related effect and P = .9 for formulation effect). Apparent oral clearance was 43 +/- 15 mL/min/kg in women compared with 75 +/- 29 in men after administration of sustained-release verapamil and 35 +/- 16 mL/min/kg in women compared with 65 +/- 31 in men after administration of regular-release verapamil (P < .05 for sex-related effect and P < .02 for formulation effect). Apparent oral clearance of both regular- and sustained-release formulations of verapamil was faster in men compared with women in contrast to findings after intravenous administration of verapamil, suggesting that intestinal processes are a factor in sex-specific difference in drug clearance. Greater verapamil and norverapamil bioavailability after administration of regular- compared with sustained-release verapamil also suggests saturable processes at the intestinal level.

Radiologic features of pediatric thalamic and hypothalamic tumors

A variety of histologic subtypes of tumor may affect the thalamus and the hypothalamus in the pediatric population. These tumors have radiologic features that are useful in predicting pathology. We discuss the radiologic findings of childhood thalamic and hypothalamic tumors and provide imaging examples.

Evaluation and comparison of a moist granulation technique to conventional methods

In the moist granulation technique (MGT), a minimum amount of liquid is used to activate a binder in a planetary mixer. Then, any excess moisture is absorbed by the addition of a moisture-absorbing substance. In the experiments described below, acetaminophen (APAP) was the model drug; polyvinylpyrrolidone (PVP) and microcrystalline cellulose (MCC) served as the binder and moisture-absorbing material, respectively. Water was used as the granulating fluid. Comparison of the MGT with direct compression (DC) and wet granulation (WG) methods was accomplished by sieve analysis (particle size) and density measurements. Moist granulation yielded an increase in particle size compared to direct compression; these results are comparable to those from the traditional wet granulation after drying and screening. Based only on the particle size, moist granulation appears comparable to conventional wet granulation for this formula. The moist granulation technique appears to have potential for the development of controlled-release formulations.

Race and sex influence clearance of nifedipine: results of a population study

OBJECTIVE

To estimate oral clearance of nifedipine and to determine demographic and clinical covariates that affect nifedipine clearance in a clinical population.

METHODS

Apparent oral clearance of nifedipine and protein binding were measured in 226 patients receiving sustained-release nifedipine formulations for hypertension and coronary artery disease (black men, n = 111; black women, n = 27; white men, n = 64; white women, n = 24). Mean age +/- SD was 71 +/- 11 years, and mean weight was 86 +/- 17 kg. Nifedipine concentrations were analyzed by HPLC, protein binding was measured by equilibrium dialysis, clearance and covariate effects were estimated by a nonlinear mixed effects population model, and statistical analyses were performed by a nonlinear mixed-effects model (clearance) and ANOVA (protein binding).

RESULTS

Clearance was significantly slower in black subjects (8.9 +/- 0.7 mL/min/kg; mean +/- SE) compared with white subjects (11.6 +/- 0.8 mL/min/kg; P = .00004) and in men compared with women (9.3 +/- 0.6 versus 12.1 +/- 1.5 mL/min/kg; P = .0021). Reported alcohol use (alcohol, 8.6 +/- 1.1 versus no alcohol, 10.8 +/- 0.6 mL/min/kg; P = .0002) and smoking status (smoker, 8.8 +/- 2.0 versus nonsmoker, 10.2 +/- 0.6 mL/min/kg; P = .0362) also affected nifedipine clearance. Race and sex had no effect on protein binding of nifedipine (P = .29 and P = .44, respectively). No effects of age, stable coronary artery disease, or reported intake of beta-blockers on nifedipine clearance were detected in this primarily elderly population with hypertension.

CONCLUSIONS

The data suggest that race, sex, and environmental factors are identifiable sources of interindividual variation in the oral clearance of nifedipine, a CYP3A substrate. Our experience also suggests that data from clinical populations may be biased with regard to age, sex, and formulation selection, and covariates may not be independently distributed, which can limit analyses.

Effect of diluents on tablet integrity and controlled drug release

The objective of this study was to evaluate the effect of diluents and wax level on tablet integrity during heat treatment and dissolution for sustained-release formulations and the resultant effect on drug release. Dibasic calcium phosphate dihydrate (DCPD), microcrystalline cellulose (MCC), and lactose were evaluated for their effect on tablet integrity during drug dissolution and heat treatment in wax matrix formulations. A newly developed direct compression diluent, dibasic calcium phosphate anhydrous (DCPA), was also evaluated. Compritol 888 ATO was used as the wax matrix material, with phenylpropanolamine hydrochloride (PPA) as a model drug. Tablets were made by direct compression and then subjected to heat treatment at 80 degrees C for 30 min. The results showed that MCC, lactose, and DCPA could maintain tablets intact during heat treatment above the melting point of wax (70 degrees C-75 degrees C). However, DCPD tablets showed wax egress during the treatment. MCC tablets swelled and cracked during drug dissolution and resulted in quick release. DCPD and lactose tablets remained intact during dissolution and gave slower release than MCC tablets. DCPA tablets without heat treatment disintegrated very quickly and showed immediate release. In contrast, heat-treated DCPA tablets remained intact through the 24-hr dissolution test and only released about 80% PPA at 6 hr. In the investigation of wax level, DCPD was used as the diluent. The drug release rate decreased as the wax content increased from 15% to 81.25%. The dissolution data were best described by the Higuchi square-root-of-time model. Diluents showed various effects during heat treatment and drug dissolution. The integrity of the tablets was related to the drug release rate. Heat treatment retarded drug release if there was no wax egress.

The electrocardiographic QT interval and its prolongation in response to medications: differences between men and women

Ventricular repolarization corrected for heart rate as measured by the electrocardiographic QTc interval differs in women compared to men. Although the mechanism remains unelucidated, the data are convincing that the effects of drugs that prolong ventricular repolarization are more likely to produce torsades de pointes arrhythmias in both healthy women and women with cardiac disease compared to men of similar ages and health status. Avoidance of such drugs and careful monitoring during necessary therapeutic administration of drugs that prolong ventricular repolarization is especially necessary in women. Electrolyte abnormalities such as hypokalemia and hypomagnesemia must be carefully avoided in patients receiving drugs that can produce QT prolongation. Because the recognition of this risk for drugs other than cardiac and psychotropic drugs has only recently emerged, it can be anticipated that the list of drugs known to produce such effects will grow.

Nutraceuticals: sorting out fact, fiction, and uncertainty

Scientific evaluation of herbal products has been limited, yet herbal products are the most commonly consumed health care products. Because of known pharmacological effects and potential interactions of many of these compounds with therapeutic drugs, a history of herbal and dietary supplement intake should be considered part of the routine medical history and should be evaluated before any changes in prescription drugs and before medical procedures.

The relationship between the timing of maternal postpartum hospital discharge and breastfeeding

This study examines the association between discharge timing and breastfeeding, controlling for demographic, economic, and health factors that influence both. Using the 1988 National Maternal and Infant Health database, maximum-likelihood modeling was used to generate 2-equation models to estimate both outcomes simultaneously. The joint estimation of breast-feeding and discharge timing demonstrates that mothers who spent 1 night in the hospital were more likely to breastfeed than mothers who spent 2 or 3 nights in the hospital (OR = 1.96, 95% C.I. 1.86-2.03). Furthermore, the model altered the association between breastfeeding and age, breastfeeding advice, and prenatal classes. In 1988, when decisions were a function of clinical judgments about readiness for discharge, early discharge was associated with an increased likelihood of breastfeeding. Instead of basing discharge solely on predetermined rules, derived largely from financial criteria, attention to the decision-making process should be an important part of newborn discharge policies.

Proper use of antiarrhythmic therapy for reduction of mortality after myocardial infarction

In this review, we summarise Vaughan Williams' classification of antiarrhythmic agents and the trials that have explored their efficacy in reducing mortality after myocardial infarction (MI). After analysing the data, it is clear that there is no role for class I antiarrhythmic agents as prophylaxis after MI since their use has been associated with increased mortality. Class II agents, i.e. beta-blockers, have demonstrated a reduction in mortality in combined and individual trials which extended for up to 6 years after the initial event. The class III drug, d,l-sotalol has been shown to have possible benefit, whereas its isomer without any beta-blocking properties, dexsotalol, has been shown to increase the incidence of arrhythmias. Amiodarone appears to reduce the incidence of deaths due to arrhythmia and sudden deaths without changing overall mortality. As a group, the calcium antagonists, class IV agents, have not been shown to reduce mortality and, in the case of nifedipine, may even increase it. Verapamil has been shown to be beneficial in one large study and may have a role in those patients in whom the use of beta-blockers is contraindicated. At this time, we recommend early implementation of beta-blockers for all patients without contraindications after MI. Further studies evaluating implantable defibrillators as primary and secondary prevention have provided significant risk reductions in certain high risk patient subsets. Future efforts will need to focus on more accurate risk stratification of post-MI patients and the role of both defibrillators and, possibly, amiodarone in improving survival.

Thermodynamic analysis of compact formation; compaction, unloading, and ejection. I. Design and development of a compaction calorimeter and mechanical and thermal energy determinations of powder compaction

The aim of this investigation was to determine and evaluate the thermodynamic properties, i.e. heat, work, and internal energy change, of the compaction process by developing a 'Compaction Calorimeter'. Compaction of common excipients and acetaminophen was performed by a double-ended, constant-strain tableting waveform utilizing an instrumented 'Compaction Simulator.' A constant-strain waveform provides a specific quantity of applied compaction work. A calorimeter, built around the dies, used a metal oxide thermistor to measure the temperature of the system. A resolution of 0.0001 degrees C with a sampling time of 5 s was used to monitor the temperature. An aluminum die within a plastic insulating die, in conjunction with fiberglass punches, comprised the calorimeter. Mechanical (work) and thermal (heat) calibrations of the elastic punch deformation were performed. An energy correction method was outlined to account for system heat effects and mechanical work of the punches. Compaction simulator transducers measured upper and lower punch forces and displacements. Measurements of the effective heat capacity of the samples were performed utilizing an electrical resistance heater. Specific heat capacities of the samples were determined by differential scanning calorimetry. The calibration techniques were utilized to determine heat, work, and the change in internal energies of powder compaction. Future publications will address the thermodynamic evaluation of the tablet sub-processes of unloading and ejection.

Gender-specific effects on verapamil pharmacokinetics and pharmacodynamics in humans

Pharmacokinetic studies of i.v. and oral racemic verapamil and 14C-erythromycin breath tests (ERBT) were performed in 84 healthy men (n = 42) and women (n = 42). Verapamil was measured by HPLC, concentration versus time data were analyzed by noncompartmental models, protein binding was measured by equilibrium dialysis, and statistical analyses were performed by ANOVA. Clearance of i.v. and p.o. verapamil was 13.7 +/- 4.3 and 58.4 +/- 35 ml/min/kg (mean +/- SD) in women compared to 12.6 +/- 3.4 and 82.6 +/- 70 ml/min/kg in men (p = 0.076). Bioavailability was higher in women (0.25 +/- 0.09) compared to men (0.20 +/- 0.09, p = 0.019) with a significant Gender x Formulation interaction (p = 0.04). ERBT were higher in women (p < 0.0001). Verapamil (i.v. and p.o.) decreased blood pressure in all subjects with greater heart rate increases after p.o. verapamil in women compared to men (p = 0.041). The findings suggest that sex-specific differences in drug metabolism may occur in both the gut and the liver and involve multiple metabolic pathways and that pharmacokinetic differences will alter pharmacodynamic responses.