Utilisation of specialist medical manpower in Malaysia

One hundred and twenty specialists from the Ministry of Health, the Universities and the private sector provided information on 4,802 patients seen over a total of two hundred and forty working days. This information was used to classify the patients into four categories based on a disease complexity classification. Each specialist's perception on the appropriateness of utilisation of his expertise was obtained. Complex cases requiring specialist expertise in management made up 69.8%, 73.5% and 19.1% of the cases of the Ministry of Health, University and private sector specialists respectively. Underutilisation was most marked with paediatricians and obstetricians in the private sector. The Specialist Register, the Programme for Accreditation of Hospitals and a National Health Financing Plan can be used to influence positively the case-mix of specialists.

Effects of ABT-761, a novel 5-lipoxygenase inhibitor, on the pharmacokinetics of a single dose of ethinyl estradiol and levonorgestrel in healthy female volunteers

ABT-761 is a second-generation 5-lipoxygenase inhibitor in clinical development for the treatment of asthma. The effects of ABT-761 on the pharmacokinetics of an oral contraceptive were assessed in 21 female adult volunteers in a phase I, multiple-dose, open-label study. Subjects received a single dose of oral contraceptive (30 microg ethinyl estradiol and 0.15 mg of levonorgestrel) on each of days 1 and 29. Oral doses of 300 mg of ABT-761 were administered once daily beginning on day 15 continuing through day 29. Statistically significant decreases in maximum concentration (Cmax) and area under the concentration-time curve (AUC) of ethinyl estradiol were observed when oral contraceptive was administered concomitantly with ABT-761 compared with administration of oral contraceptive alone. The mean elimination rate constant of ethinyl estradiol increased by 30% (a mean decrease of 3.8 hours in half-life), and the mean apparent volume of distribution during the terminal phase (Vd(beta)/F) of ethinyl estradiol increased by 73% in the presence of ABT-761. Mean Cmax and AUC values for norgestrel decreased by 12% and 10%, respectively, when administered with ABT-761. Mean values for time to Cmax (tmax), terminal rate constant (beta), half-life (t1/2), and Vd(beta)/F of norgestrel were similar when oral contraceptive was administered alone or concomitantly with ABT-761. The mechanism responsible for the effect of ABT-761 on the clearance of ethinyl estradiol remains undefined. Because results of previous multiple-dose studies of ABT-761 do not provide any evidence of autoinduction, the effects of ABT-761 on the pharmacokinetics of ethinyl estradiol are more likely related to absorption of ethinyl estradiol.

Enhanced secretory production of a single-chain antibody fragment from Bacillus subtilis by coproduction of molecular chaperones

Formation of inclusion bodies is a major limiting factor for secretory production of an antidigoxin single-chain antibody (SCA) fragment from Bacillus subtilis. To address this problem, three new strains with enhanced production of molecular chaperones were constructed. WB600BHM constitutively produces the major intracellular molecular chaperones in an appropriate ratio without any heat shock treatment. This strain reduced the formation of insoluble SCA by 45% and increased the secretory production yield by 60%. The second strain, WB600B[pEPP], overproduces an extracytoplasmic molecular chaperone, PrsA. An increase in the total yield of SCA was observed. The third strain, WB600BHM[pEPP], coproduces both intracellular and extracytoplasmic molecular chaperones. This led to a further reduction in inclusion body formation and a 2.5-fold increase in the secretory production yield. SCA fragments secreted by this strain were biologically active and showed affinity to digoxin comparable to the affinity of those secreted by strains without overproduction of molecular chaperones. Interestingly, accumulation of a pool of periplasmic SCA was observed in the PrsA-overproducing strains. This pool is suggested to represent the secreted folding intermediates in the process of achieving their final configuration.

Endobronchial metastasis from an occult papillary thyroid carcinoma: a case report

It is well known that occult papillary thyroid cancers can result in regional lymph node metastasis. However, this small, clinically undetectable cancer rarely causes distant metastasis; moreover, an endobronchial presentation has not been described previously. We report on a 48-year-old man who experienced hemoptysis. A fiberoptic bronchoscopic biopsy established the diagnosis of endobronchial metastasis in the absence of clinically apparent thyroid cancer. After the patient was treated with a total thyroidectomy and radioactive iodine (131I), a whole body radioiodine scan revealed no evidence of distant functioning metastasis. A histological evaluation of the thyroid gland showed the presence of a 0.2 x 0.2 x 0.2 cm nodule in the right lobe. A left pneumonectomy was undertaken to treat the distant metastasis of the disease. Since most papillary thyroid carcinomas are curable, an aggressive surgical approach to the solitary metastasis is indicated.

Dose-proportional pharmacokinetics of a new 5-lipoxygenase inhibitor, ABT-761, in healthy volunteers

ABT-761, a new potent 5-lipoxygenase inhibitor, is under development for the treatment of asthma. The pharmacokinetics and dose proportionality of ABT-761 after single doses (10-160 mg) of ABT-761 in 24 healthy male volunteers were investigated in a double-blind, placebo-controlled study. The compound was well tolerated, with no clinically significant effects on vital sign measurements, hematological parameters, clinical chemistry, urinalysis, or electrocardiogram. The plasma concentration-time profile of ABT-761 indicates that the drug declines in a monoexponential fashion after moderately slow absorption, with a tmax value of approximately 4 h. The terminal elimination t1/2 averaged 15 h, and was dose independent. ABT-761 mean values of Cmax and AUC were linearly related to drug dose. ABT-761 is well tolerated in healthy volunteers and the pharmacokinetics are linear in the single-dose range between 10 and 160 mg.

Agreement on responses to respiratory illnesses questionnaire

The prevalence of respiratory symptoms and illnesses among 2225 schoolchildren in Hong Kong was studied by questionnaires administered independently to them and their parents. The agreement was generally poor for respiratory symptoms. The disparity shows the need for cross validation of clinical information in history taking.

Extreme selection strategies in gene mapping studies of oligogenic quantitative traits do not always increase power

It is well known that obtaining adequate statistical power to detect linkage to or association with genes for complex quantitative traits can be very difficult. In response, investigators have developed a number of power-enhancing strategies that consider restraints such as genotyping (and/or phenotyping) costs. In the context of both association and sib pair linkage studies of quantitative traits, one of the most widely discussed techniques is the selective sampling of phenotypically extreme individuals. Several papers have demonstrated that such extreme sampling can markedly increase power (under certain circumstances). However, the parenthetical phrase in the previous sentence has generally not been made explicit and it appears to be implied that the more phenotypically extreme the individuals, the more power one has. In this paper, we show by simulation that this is not true under all circumstances. In particular, we show that under oligogenic models, where some biallelic quantitative trait loci (QTLs) have markedly asymmetric allele frequencies and large mean displacement among genotypes, and others have less asymmetric allele frequencies and smaller mean displacement among genotypes, power to detect linkage to or association with the latter QTL can actually decrease by sampling more extreme sib pairs. This suggests that more extreme sampling is not always better. The 'optimal' sampling scheme may depend on both what one suspects the underlying genetic architecture to be and which of the oligogenic QTL one has greatest interest in detecting.

Engineering of plasmin-resistant forms of streptokinase and their production in Bacillus subtilis: streptokinase with longer functional half-life

The short in vivo half-life of streptokinase limits its efficacy as an efficient blood clot-dissolving agent. During the clot-dissolving process, streptokinase is processed to smaller intermediates by plasmin. Two of the major processing sites are Lys59 and Lys386. We engineered two versions of streptokinase with either one of the lysine residues changed to glutamine and a third version with both mutations. These mutant streptokinase proteins (muteins) were produced by secretion with the protease-deficient Bacillus subtilis WB600 as the host. The purified muteins retained comparable kinetics parameters in plasminogen activation and showed different degrees of resistance to plasmin depending on the nature of the mutation. Muteins with double mutations had half-lives that were extended 21-fold when assayed in a 1:1 molar ratio with plasminogen in vitro and showed better plasminogen activation activity with time in the radial caseinolysis assay. This study indicates that plasmin-mediated processing leads to the inactivation of streptokinase and is not required to convert streptokinase to its active form. Plasmin-resistant forms of streptokinase can be engineered without affecting their activity, and blockage of the N-terminal cleavage site is essential to generate engineered streptokinase with a longer in vitro functional half-life.

Pharmacokinetics and pharmacodynamics of single and multiple oral doses of a novel 5-lipoxygenase inhibitor (ABT-761) in healthy volunteers

OBJECTIVE

This study evaluated the safety, pharmacokinetics and pharmacodynamics of ABT-761 [R(+)-N-[3-[5-(4-fluorophenylmethyl)-2-thienyl]-1- methyl-2-propynyl]-N-hydroxyurea], a new N-hydroxyurea analog.

METHODS

This was a randomized, double-blind, placebo-controlled, single- and multiple-dose (15-day) study of ABT-761 (50 to 200 mg/day) in healthy, nonsmoking adult male volunteers. The pharmacokinetics were evaluated by investigation of the time- and dose-dependent effects of ABT-761, and the pharmacologic selectivity of ABT-761 was evaluated based on calcium ionophore-stimulated leukotriene B4 (LTB4) and thromboxane B2 (TXB2) biosynthesis ex vivo in whole blood.

RESULTS

After single and multiple doses, mean observed time to reach maximum concentration values of ABT-761 ranged from 4.0 to 7.5 hours. Mean values for maximum concentration and area under the plasma concentration-time curve from 0 to 24 hours increased approximately linearly with dose. Mean terminal half-life and apparent volume of distribution during the terminal elimination phase of ABT-761 ranged from 15.4 to 17.8 hours and 69.5 to 78.9 L, respectively, and was dose independent. Steady state was reached on day 11 after multiple dosing. Less than 0.05% of unchanged ABT-761 was recovered in urine within the 24-hour period after day 15 dosing. Population ABT-761 plasma concentration at which 50% of the maximum possible inhibition was observed for LTB4 inhibition was 0.24 microgram/ml. No differences in mean TXB2 inhibition were observed between the subjects receiving ABT-761 and placebo.

CONCLUSIONS

These results indicate that ABT-761 is a potent and selective inhibitor of 5-lipoxygenase and the pharmacokinetics of ABT-761 are time and dose independent between 50 and 200 mg/day after single and multiple dosing.

Lack of CYP3A inhibition effects of sertindole on terfenadine in healthy volunteers

The effect of sertindole (a new selective antipsychotic compound) on the pharmacokinetic disposition of terfenadine was investigated. Thirteen subjects who completed the study received a single 120 mg dose of terfenadine alone or with concomitant 20 mg sertindole daily. The mean values for terfenadine Cmax (alone: 2.42 +/- 1.48 ng/ml, in combination: 2.99 +/- 1.85 ng/ml) and AUC (29.6 +/- 18.9 vs 37.9 +/- 23.4 ng x hr/ml) did not change statistically significant in the presence of sertindole (p > 0.05). Similarly, the mean Cmax (531 +/- 195 vs 506 +/- 190 ng/ml) and AUC (3,728 +/- 1,163 vs 4,003 +/- 1,739 ng x hr/ml) values of carboxyterfenadine did not change statistically significant in the presence of sertindole (p > 0.05). The other pharmacokinetic parameters of terfenadine and carboxyterfenadine such as Tmax, t1/2, as well as the carboxyterfenadine to terfenadine Cmax and AUC ratios did not change in the presence of sertindole. Although terfenadine is a substrate for CYP3A (cytochrome P-450 3A), while sertindole is a substrate for both CYP2D6 and CYP3A4, the results in this study suggest that sertindole, at a clinical dose, is not an inhibitor of the metabolism of terfenadine.

Lack of multiple dosing effect of sertindole on the pharmacokinetics of alprazolam in healthy volunteers

The effect of sertindole (a new selective antipsychotic compound) on the pharmacokinetic disposition of alprazolam was investigated. Fourteen subjects who completed the study received a single 1 mg dose of alprazolam without or with concomitant sertindole 12 mg daily. Coadministration of sertindole and alprazolam led to a half-hour decrease (P < 0.05) in mean Tmax value (alone: 1.2 h, in combination: 0.7 h) and a 1.6-h increase in the mean t1/2 value (12.5 +/- 3.2 versus 14.3 +/- 3.4 h, P < 0.05) of alprazolam. The mean Cmax (18.5 +/- 4.9 versus 18.5 +/- 4.8 ng/ml) and AUC (266 +/- 68 versus 275 +/- 57 ng x h/ml) values of alprazolam did not change statistically significantly in the presence of sertindole (P > 0.05). These pharmacokinetic changes are minor and not considered to be of clinical significance. Although both sertindole and alprazolam are substrate for CYP3A4 (cytochrome P-450 3A4), the results in this study suggest that sertindole is not an inhibitor of the metabolism of alprazolam.

The effect of erythromycin on the CYP3A component of sertindole clearance in healthy volunteers

The effect of erythromycin on the pharmacokinetic disposition of oral sertindole, a new antipsychotic compound, was investigated. Ten subjects who completed the study received a single 4-mg dose of sertindole without or with concomitant erythromycin 250 mg taken orally 4 times daily. Coadministration of sertindole and erythromycin led to a 33% decrease (P < 0.05) in mean (+/- SD) time to reach maximum plasma concentration (tmax) value and a 15% elevation (P < 0.05) in the mean maximum plasma concentration (Cmax) value of sertindole. The mean area under the concentration-time curve (AUC) value of sertindole did not change significantly in the presence of erythromycin (alone: 159 +/- 111 ng.hr/mL, in combination: 179 +/- 144 ng.hr/mL, P > 0.05). The presence of erythromycin also significantly increased the dehydrosertindole Cmax and AUC means by 16% and 21%, respectively, possibly due to inhibition of the CYP3A metabolic isozyme responsible for the elimination of this metabolite. The rate of absorption of sertindole and the rate of appearance of dehydrosertindole in the systemic circulation after a 4-mg sertindole single dose were slightly enhanced by concomitant dosing of erythromycin. In conclusion, there is a small but noticeable effect of erythromycin on the pharmacokinetic disposition of sertindole. The effects are believed to have little clinical significance.

[O-ethyl 14C]phenacetin O-deethylase activity in human liver microsomes

The activity of human liver microsomal cytochrome P450 1A2 (CYP1A2) is readily estimated by following the O-deethylation of [O-ethyl 14C]phenacetin (PODase). The basis of the assay is the quantitative measurement of [14C]acetaldehyde, remaining in the supernatant of assay incubates, after extraction of unmetabolized [O-ethyl 14C]phenacetin with charcoal. In the presence of native human liver microsomes (K(m) = 54 +/- 27 microM; V(max) = 14 +/- 2.3 nmol/hr/mg; mean +/- SD; N = 3 different livers) and human B-lymphoblastoid cell microsomes containing cDNA-expressed CYP1A2 (K(m) = 46 microM; V(max) = 55 nmol/hr/nmol CYP), PODase activity conformed to monophasic Michaelis-Menten kinetics. Furthermore, PODase activity in a panel of microsomes prepared from a series of human livers was significantly correlated (r = 0.91; p < 0.001; N = 11) with CYP1A2-selective 7-ethoxyresorufin O-deethylase activity, and was markedly inhibited (> or = 92%) by furafylline (FURA, IC50 = 0.4 microM) and 7,8-benzoflavone (ANF, IC50 = 0.1 microM), two well known CYP1A2 inhibitors. Inhibitors selective for other forms of CYP (e.g. CYP3A, CYP2C, CYP2D6, CYP2E1) elicited a marginal effect (< or = 17% inhibition) at relatively high concentrations (> or = 10.K(i)). It is concluded that the inhibition of human liver microsomal CYP1A2 activity can be readily determined by using a charcoal-based radiometric method employing [O-ethyl 14C]phenacetin as substrate.

Effects of food, antacid, and dosage form on the pharmacokinetics and relative bioavailability of sertindole in healthy volunteers

The pharmacokinetic disposition and relative bioavailability of sertindole administered as a tablet dosage form under fasting conditions, in the presence of food, in the presence of antacid, and as solution was studied in a four-way crossover in young healthy male volunteers. Overall, tablet dosing after a meal or Maalox had no effect on t1/2 or AUC values when compared to fasting conditions, but increased the tmax and decreased the Cmax values slightly. The mean relative bioavailabilities of sertindole administered as tablets after fasting, with food, and with Maalox are 99, 104, and 98%, respectively, compared to sertindole solution. Therefore, sertindole can be administered with and without food and without regard to coadministration of antacids.

Pharmacokinetics of sertindole in healthy young and elderly male and female subjects

OBJECTIVE

The pharmacokinetic disposition of oral sertindole, a new selective antipsychotic compound, in young and elderly male and female subjects was investigated.

STUDY DESIGN

A total of 46 subjects (12 young males, 11 elderly males, 11 young females, and 12 elderly females) received 4 mg/day sertindole (once a day; days 1 through 3) for 3 consecutive days, 8 mg/day sertindole for 3 consecutive days (days 4 through 6), and 12 mg/day sertindole for 10 consecutive days (days 7 through 16).

RESULTS

Age and gender did not appear to have any effect on the plasma binding of sertindole, despite a lower albumin concentration in elderly subjects. After multiple dosing of 12 mg sertindole, the mean peak plasma concentration (Cmax) values for young and elderly female subjects were 20% and 31% higher than those observed for male subjects of comparable age (p < 0.05). The mean values for area under the plasma concentration-time curve [AUC(0-24)] of female subjects were 29% higher than those observed in male subjects of similar age (p < 0.05). There were no statistically significant age-related differences in Cmax and AUC(0-24) (or apparent total plasma clearance), and there were no gender- or age-related differences for the elimination rate constant or values for apparent volume of distribution during the terminal elimination phase after the last 12 mg dose on day 16 (p > 0.05).

CONCLUSIONS

There are no differences between young and elderly subjects in the absorption and elimination of sertindole. The higher Cmax and AUC values in females may be a result of a higher extent of absorption or a dependence of sertindole clearance on lean body mass.

Expression of the Bacillus licheniformis PWD-1 keratinase gene in B. subtilis

The kerA gene which encodes the enzyme keratinase was isolated from the feather-degrading bacterium Bacillus licheniformis PWD-1. The entire gene, including pre-, pro- and mature protein regions, was cloned with Pker, its own promoter, P43, the vegetative growth promoter, or the combination of P43-Pker into plasmid pUB18. Transformation of the protease-deficient strain B. subtilis DB104 with these plasmids generated transformant strains FDB-3, FDB-108 and FDB-29 respectively. All transformants expressed active keratinase in both feather and LB media, in contrast to PWD-1, in which kerA was repressed when grown in LB medium. With P43-Pker upstream of kerA, FDB-29 displayed the highest activity in feather medium. Production of keratinase in PWD-1 and transformants was further characterized when glucose or casamino acids were supplemented into the feather medium. These studies help understand the regulation of kerA expression and, in the long run, can help strain development and medium conditioning for the production of this industrially important keratinase.

Castleman's disease: a case report

Castleman's disease is a rare, benign disorder most commonly located in the mediastinum as a solitary mass. It is a lymphoid tissue disorder characterized by lymphoid proliferation. In this paper we describe a case of asymptomatic interlobar fissure tumor, localized Castleman's disease, hyaline vascular type, in a 30-year-old female. The tumor arose from the interlobar fissure between the right middle and lower lobes. Laboratory data revealed hypochromic microcytic anemia, similar to that found in iron deficiency, and an elevated erythrocyte sedimentation rate. She underwent video-assisted thoracic surgery for excision of the tumor. Anemia disappeared two months after surgery. No recurrence of the lung tumor was seen 19 months following surgery and she remains well.

Trends of infant mortality in Hong Kong (1956-90) and evaluation of preventable infant deaths

OBJECTIVE

This study describes the time trends for infant mortality in Hong Kong and aims to develop statistical models that can be used to predict changes of infant mortality in places already having low levels of infant mortality.

METHODOLOGY

Data on births and deaths of infants in Hong Kong during the years 1956-90 were analysed annually as well as by aggregating the data into seven consecutive quinquennia. To assess the contribution of preventable infant deaths, causes for infant deaths were classified into two broad categories: (i) congenital anomalies; and (ii) preventable diseases. A simple linear regression model was used to analyse the time trend of the mortality rate of the preventable diseases (PIMR) over the seven quinquennia.

RESULTS

During the period 1956-90, the infant mortality rate fell from 60.9 in 1956-5.9 per 1000 in 1990 and the neonatal mortality rate fell from 24.2-3.8 per 1000. There was no clear time trend observed for infant mortality of congenital anomalies. However, the time trend for PIMR (log scale) was very close to a straight line and simple linear regression modelling showed a R2 of 0.9970.

CONCLUSION

As the infant mortality rate (IMR) falls to below 30 per 1000, the further rate of decrease becomes less predictable from the regression model of the IMR. By removing the portion of deaths attributable to congenital anomalies, the further decrease in infant mortality became more predictable down to very low levels of IMR.

Detection of toxic organometallic complexes in wastewaters using algal assays

Chlorella (a unicellular green alga) and Cladophora (a filamentous alga) were used in algal assays to identify the presence and toxicity of organometallic complexes in four industrial wastewaters. Toxicities of inorganic Pb and organometallic compounds (trimethyl, tetramethyl and tetraethyl leads, cacodylic acid and Cu-picolinate) were examined, using algal cells grown in 10% BBM solution. Inorganic Pb and organometallic compounds altered the fine structure of Chlorella cells in a distinguishable manner. X-ray microanalysis revealed that organometallic compounds accumulated in the neutral lipids of Cladophora cells. By applying the above techniques to the wastewater assays, two of the four wastewaters tested were found to contain organometallic complexes. Wastewater from a chemical company contained only traces of organo-Cu, but one mining effluent contained significant quantities of organo-Cu and organo-Pb, and traces of organo-Cr and organo-Tl (thallium). These studies suggest that X-ray microanalysis of algae may be a useful tool in identifying aquatic systems contaminated with metals and organometallic compounds.

Pharmacokinetics of sertindole and dehydrosertindole in volunteers with normal or impaired renal function

OBJECTIVE

To study the effect of renal impairment on the pharmacokinetics of sertindole.

METHODS

A single 4 mg oral dose of sertindole was given to normal subjects (n = 6) and subjects with various degrees of impaired renal function (n = 18) classified into mild, moderate, and severe/hemodialysis based on their creatinine clearance). The relationships between the pharmacokinetic parameters and the degree of renal impairment were investigated using regression analysis with creatinine clearance as an explanatory variable along with body weight. Subjects were also genotyped for CYP2D6-A or 2D6-B mutations.

RESULTS

The mean CL/f and t1/2 values of sertindole ranged from 14 to 31 1.h-1 and from 73 to 93 h, respectively, and were not significantly related to creatinine clearances. There was no indication of any influence of creatinine clearance on the fraction of sertindole (0.994-0.995) binding to plasma proteins. The total fraction of the sertindole dose removed by dialysis was less than 0.1% Subjects with B/B genotype (n = 2) for CYP2D6 were associated with a distinctly lower clearance of sertindole (6.3 vs 25.3 1.h-1) than subjects with wt/wt genotype for CYP2D6.

CONCLUSIONS

Since the pharmacokinetics of sertindole are unchanged by renal impairment, dosage adjustment does not appear to be necessary for subjects with various degrees of renal insufficiency or subjects with renal failure requiring hemodialysis.

Expanded version of PKSIM for pharmacokinetic simulations of both metabolite and parent drugs

We recently described a computer software package for pharmacokinetic simulations called PKSIM. The programs are useful for studying drugs that display either a one-, two-, or three-compartment body model with linear or nonlinear elimination following single or multiple dosing. The practicality of PKSIM owes to its user-friendliness and flexibility to study the impact of pharmacokinetic perturbations and dosage regimens on the drug's concentration-time profile on a real-time basis. The interactive nature of PKSIM allows the test variables to be easily changed after each simulation. High-resolution graphic capabilities also permit presentation of pharmacokinetic profile in various body compartments, either individually or collectively on a single graph. The capability of PKSIM was recently extended to include simulations of both parent drug and metabolite, which adds to the value of the package. The present paper describes in detail the functions of these new features and how they can be applied to better comprehend the pharmacokinetic interdependency between the parent drug and metabolite. In addition to the dose, dosing regimen and rate of drug absorption, influences on the kinetic profiles of parent drug and metabolite by other variables such as formation rate of the metabolite, tissue distribution, tissue redistribution, elimination rates and distribution volume of both entities can be studied with minimal efforts. These new features can be particularly helpful for researchers to study prodrugs and drugs that produce active or toxic metabolites, or better understand the basic concepts of metabolite kinetics.

Effects of divalproex sodium on amitriptyline and nortriptyline pharmacokinetics

BACKGROUND

Divalproex sodium has been found to be efficacious in the prophylaxis of migraine headaches and the management of the manic phase of bipolar syndrome. Because amitriptyline is also prescribed in these patient populations, data are needed on their potential for interaction.

METHODS

The effect of concomitant administration of divalproex sodium on the pharmacokinetics of amitriptyline and its active metabolite, nortriptyline, was investigated in an open-label, sequential, two-period phase I study. Ten healthy male and five healthy female subjects received 50 mg amitriptyline hydrochloride on two occasions: (1) alone (period 1) and (2) 2 hours after receiving the ninth dose of 500 mg divalproex sodium (Depakote) administered once every 12 hours (period 2).

RESULTS

Amitriptyline area under the curve was increased 31% from the combined effect of decreased first-pass metabolism and inhibition of systemic metabolism. The elevated nortriptyline plasma levels reflected primarily the increase in amitriptyline concentrations but also appeared to involve modest inhibition of nortriptyline elimination. For the sum of amitriptyline and nortriptyline concentrations, the peak plasma concentration mean was 19% higher with concomitant divalproex dosing. The mean area under the curve for the sum of amitriptyline and nortriptyline concentrations was 42% higher with concomitant divalproex dosing than it was for dosing with amitriptyline alone.

CONCLUSION

These results suggested that a lower dose of amitriptyline might be considered when divalproex is administered concomitantly.

X-ray and NMR structure of human Bcl-xL, an inhibitor of programmed cell death

THE Bcl-2 family of proteins regulate programmed cell death by an unknown mechanism. Here we describe the crystal and solution structures of a Bcl-2 family member, Bcl-xL (ref. 2). The structures consist of two central, primarily hydrophobic alpha-helices, which are surrounded by amphipathic helices. A 60-residue loop connecting helices alpha1 and alpha2 was found to be flexible and non-essential for anti-apoptotic activity. The three functionally important Bcl-2 homology regions (BH1, BH2 and BH3) are in close spatial proximity and form an elongated hydrophobic cleft that may represent the binding site for other Bcl-2 family members. The arrangement of the alpha-helices in Bcl-xL is reminiscent of the membrane translocation domain of bacterial toxins, in particular diphtheria toxin and the colicins. The structural similarity may provide a clue to the mechanism of action of the Bcl-2 family of proteins.