Long-term treatment of anxiety and risk of withdrawal. Prospective comparison of clorazepate and buspirone

Risk of withdrawal was investigated in a prospective, double-blind comparison of clorazepate dipotassium, a benzodiazepine with a long half-life, and the nonbenzodiazepine buspirone hydrochloride in the long-term treatment of anxious outpatients. Patients were treated with therapeutic doses of clorazepate dipotassium (15 to 60 mg/d) or buspirone hydrochloride (10 to 40 mg/d) for six continuous months before their tranquilizer therapy was blindly and abruptly stopped. There was a significant increase in symptom severity consistent with a withdrawal reaction for the clorazepate group but not the buspirone group. For the clorazepate group, there was a suggestion that previous discontinuous exposure to benzodiazepines might sensitize patients to subsequent withdrawal effects. For the buspirone group, a higher dropout rate raised questions about patient satisfaction with therapy in this rather chronically anxious population.

Methemoglobin formation resulting from administration of candidate 8-aminoquinoline antiparasitic drugs in the dog

In vivo methemoglobin (MHb) formation caused by five 8-aminoquinoline compounds was tested in beagle dogs. Male beagle dogs were dosed orally once per day at 0.0116 mmol/kg for 4 consecutive days with primaquine (8-[4-amino-1-methylbutyl)amino]-6-methoxyquinoline, diphosphate), three candidate 8-aminoquinoline antimalarial drugs (WR 225,448 5-(3-trifluoromethyl)phenoxy-4-methyl primaquine, succinate); WR 238,605 2,6-dimethoxy-5-(3-trifluoromethyl)phenoxy-4-methyl primaquine, succinate; or WR 242,511 5-hexoxy-4-methyl primaquine, diphosphate dihydrate), or a candidate 8-aminoquinoline antileishmanial drug WR 6026 (8-[(6-diethylamino)amino]-6-methoxy-4-methyl quinoline, dihydrochloride). MHb and total hemoglobin levels were determined daily prior to dosing and for 29 days after drug administration. All compounds caused prolonged levels of MHb that peaked at Days 4 to 5 with disappearance half-lives of 5 to 9 days. Peak percentage MHb of primaquine, WR 6026, WR 238,605, WR 225,448, and WR 242,511 was 6.3, 20.7, 16.0, 25.3, and 48.1%, respectively. Total MHb as measured by area under the time-concentration curve was highest for WR 242,511, followed by WR 225,448, WR 238,605, WR 6026, and primaquine, respectively. The results of this study, in conjunction with other toxicity and efficacy studies, have been utilized to select one of these compounds for development as a replacement for the antimalarial drug primaquine, and also to characterize the MHb-forming properties of WR 6026.

Effectiveness of silicone oil removal from rabbit eyes

Silicone oil (1000 and 12,500 cs) and fluorosilicone oil (1000 and 10,000 cs) were dyed red and injected into a gas-created space in the vitreous cavity of 51 rabbit eyes. Later the oils were removed from the vitreous cavity either by lavage with balanced salt solution (group 1, 27 eyes) or by injecting a sodium hyaluronate solution, followed by lavage with balanced salt solution (group 2, 24 eyes). The average amount of oil retained in the vitreous cavity in group 1 was 0.0675 ml, and occasionally a large amount of oil was found (more than 0.1 ml in 30% of eyes). The average amount of oil retained in group 2 was 0.0114 ml, and no eye retained more than 0.1 ml of oil. The difference between the two groups was statistically significant (p less than 0.02), but there was no significant difference in oil retention within either group between the different kinds of oils, or between different viscosities of oil. The data suggest that residual oil can persist in the vitreous cavity despite thorough lavage, and that removal of silicone oil with the use of a sodium hyaluronate solution significantly lowers the risk of a large amount of residual silicone oil that is occasionally seen with conventional removal methods.

Irreversible inhibition of the human placental NADP-linked 15-hydroxyprostaglandin dehydrogenase/9-ketoprostaglandin reductase by glutathione thiosulfonate

Oxidation of glutathione disulfide by a mixture of performic and hydrochloric acids leads to the formation of several compounds that are stronger inhibitors than glutathione disulfide of the placental enzyme that possess both NADP-linked 15-hydroxyprostaglandin dehydrogenase and 9-ketoprostaglandin reductase activities. The only one of these inhibitors that has been identified is glutathione thiosulfonate. The others are unstable and may include glutathione sulfinyl sulfone and glutathione disulfone. Since the enzyme appears to have a glutathione binding site in close proximity to its active site and glutathione thiosulfonate reacts with free sulfhydryl groups, the effects of this thiosulfonate on the enzyme were examined in more detail. Glutathione thiosulfonate and methyl methanethiosulfonate cause a time-dependent irreversible inhibition of both the hydroxyprostaglandin dehydrogenase and the ketoprostaglandin reductase activities, presumably by reacting with a free sulfhydryl at the prostaglandin binding site. Experiments with PGA1-glutathione show that this sulfhydryl is not necessary for the catalytic activity of the enzyme as long as the substrate can bind at the glutathione site.

Glutathione mixed disulfide inhibitors of the human placental NADP-linked 15-hydroxyprostaglandin dehydrogenase

Six glutathione-containing inhibitors of the human NADP-linked 15-hydroxyprostaglandin dehydrogenase have been isolated from placental homogenates. Glutathione disulfide is one of these inhibitors. Although the structures of the other five have not been fully elucidated, all are disulfides. Studies with these compounds and with other mixed disulfides have shown that the glutathione mixed disulfides of beta-mercaptopyruvate, mercaptoacetate, and beta-mercaptolactate are more effective inhibitors of the enzyme than are the glutathione-containing mixed disulfides isolated from placental homogenates. beta-Mercaptolactate is particularly noteworthy because of its low Ki (0.13 microM). The results reported here suggest that the activity of the prostaglandin dehydrogenase may be influenced in vivo by various glutathione mixed disulfides.

Analysis of artesunic acid and dihydroqinghaosu in blood by high-performance liquid chromatography with reductive electrochemical detection

A new high-performance liquid chromatography (HPLC) method using reductive electrochemical detection has been developed for the analysis of the antimalarial drugs artesunic acid (ARTS) and dihydroqinghaosu (DQHS) in blood. Presently, this method has been validated to 4 micrograms/ml for ARTS and 200 ng/ml for DQHS. Pharmacokinetic studies in the rabbit show that after intravenous administration (100 mg/kg) ARTS is metabolized rapidly to DQHS and has a t1/2 of 1.7 min in blood. DQHS data were fit to non-linear regression models consisting of the sum of two exponential terms. For phases 1 and 2, t1/2 values of 3.0 +/- 0.4 and 29 +/- 2 min were calculated, respectively. In vitro studies in which ARTS was incubated with blood from various species show that rabbit blood hydrolyzes ARTS at a much greater rate than rat or human blood. Incubation of ARTS with rabbit blood in the presence or absence of diisopropylfluorophosphate suggested that this hydrolysis reaction is catalyzed by plasma and red blood cell esterases. These results suggest that future pharmacokinetic studies in both animals and man should focus on the measurement of DQHS rather than ARTS.

Use of high-density fluorosilicone oil in open-sky vitrectomy

During prolonged open-sky vitrectomy, fluid accumulates in the suprachoroidal and subretinal spaces and the resultant ballooning of the choroid and of the retina interferes with the surgery. Fluorosilicone oil (polymethyl-3,3,3-trifluoropropylsiloxane) with a specific gravity of 1.28 was tested for use as a temporary vitreous substitute during open-sky vitrectomy. After open-sky vitrectomy and bullous retinal detachment in pigmented rabbits, fluorosilicone oil flattened the retina completely in nine of nine eyes, whereas 1% sodium hyaluronate solution flattened the retina completely in only four of nine eyes. The flattening effect of fluorosilicone oil on the retina was also better than that of 1% sodium hyaluronate in an experiment with retinal detachment and giant retinal tear after open-sky vitrectomy.

Structure-activity relationships of putative primaquine metabolites causing methemoglobin formation in canine hemolysates

A rapid and reproducible in vitro test system was developed to measure the methemoglobin (MHb)-forming properties of various 8-aminoquinoline derivatives. Initial rates and extents of reaction were measured spectrophotometrically with either canine hemolysates from which ferrihemoglobin reductase was removed, or with purified human oxyhemoglobin (Hb). The results demonstrate that primaquine derivatives that can be oxidized to quinones or iminoquinones (5-hydroxy,6-desmethyl primaquine; 5-hydroxyprimaquine; 5,6-dihydroxy-8-aminoquinoline; and 5-hydroxy, 6-methoxy-8-aminoquinoline) are potent MHb-forming compounds. Studies on the extent of reaction in hemolysates and purified oxyhemoglobin suggest that the extent of MHb formation may be limited by the rate at which the corresponding iminoquinones or quinones arylate nucleophiles. The effects of glutathione, mannitol, ascorbate, and superoxide dismutase on the rate and extent of hemoglobin oxidation by 5,6-dihydroxy-8-aminoquinoline suggest that these compounds oxidize Hb similar to the mechanism known for dimethylaminophenol (DMAP), in which Hb oxidizes the quinoline to semiquinone radical and quinone species which are the oxidizing and arylating agents.

Six-week trial with diazepam: some clinical observations

Side effects, improvement, and predictors of response were examined in 295 patients treated for greater than or equal to 1 week with diazepam; 234 of these patients completed 6 weeks of treatment. The greatest improvement occurred during the first week of treatment. Sedation was the predominant side effect. Predictors of improvement included low educational level, lack of previous treatment, presence of precipitating stress, low occupational and/or family adjustment, low levels of trait anxiety, and high levels of state anxiety.

Metabolism of a potential 8-aminoquinoline antileishmanial drug in rat liver microsomes

The metabolism of the 8-aminoquinoline, 8-(6-diethylaminohexylamino)-6-methoxy-lepidine dihydrochloride (WR 6026 X 2HCl), was studied in a rat hepatic microsomal system. The results show that WR 6026 X 2HCl was metabolized into two more polar compounds. The structures of these metabolites as proven by gas chromatography-mass spectrometry, ultraviolet absorption, and high performance liquid chromatography were: 8-(6-ethylaminohexylamino)-6-methoxy-lepidine (metabolite 1) and 8-(6-diethylaminohexylamino)-6-methoxy-4-hydroxymethyl quinoline (metabolite 2). The formation of both metabolites was NADPH dependent and also linearly dependent on incubation time and microsomal protein concentration at 0.24 mM WR 6026 X 2 HCl. Studies on the effects of pretreatment of animals with either phenobarbital or Aroclor 1254 suggest that cytochrome P-450 isozymes catalyzed both N-deethylation and hydroxylation reactions. N-deethylase activity was induced by either pretreatment: however, hydroxylase activity was unaffected by phenobarbital pretreatment and significantly elevated by Aroclor 1254 pretreatment. These results suggest that these two reactions are catalyzed by different cytochrome P-450 isozymes. The formation of these two metabolites in vivo may play an important role in the antileishmanial activity of WR 6026 X 2HCl.

High-performance liquid chromatographic method for the analysis of a candidate 8-aminoquinoline antileishmanial drug using oxidative electrochemical detection

An analytical method was developed for the quantitation of a candidate antileishmanial drug, 6-methoxy-8-(6-diethylaminohexylamino)-4-methylquinoline, dihydrochloride, in canine plasma. The assay utilized internal standard technique with a structural similar 8-aminoquinoline, 6-methoxy-8-(7-diethylaminoheptylamino)-4-methylquinoline, dihydrochloride, as the internal standard. The method employs a liquid-solid extraction procedure with prepackaged silica gel columns upon which the drug and internal standard are adsorbed, then selectively washed and eluted. Reversed-phase chromatography was then employed to analyze the extracted sample by means of oxidative electrochemical detection at +0.75 V. Good accuracy and precision were obtained over the range of concentration tested (10-1500 ng/ml plasma). Analyses of plasma samples from human volunteers given the drug demonstrate the method is also suitable for analysis of human plasma samples. The entire procedure is relatively simple and requires only 1 ml of plasma.

Deficiencies and improvement of methemoglobin assay

A day-to-day variability in results was encountered when using the Dubowski method for the routine clinical determination of methemoglobin in blood. Therefore, studies were performed to determine the source(s) of variability in the method as described by Dubowski. It was determined that complete lysing of red blood cells is dependent upon both temperature of the buffer and the amount of lysing agent. Low buffer temperatures (less than 14 degrees C) produced highly variable results. This variability can be reduced by increasing the level of lysing agent to 40 mg per 20 mL of diluted blood. It was found that by using 37 degrees C buffer solution temperature and 40 mg Triton X-100 as lysing agent per 20 mL of diluted blood (1:20 with 0.25M sodium phosphate buffer, pH 7.4), the precision (percent coefficient of variation = 2%) and the accuracy (percent coefficient variation = 5.5%) were excellent.

Gentamicin penetration into diseased appendix tissue

Gentamicin concentrations in appendix tissue, serum, and peritoneal fluid were obtained in suspected cases of gangrenous or perforated appendicitis. Despite widely ranging gentamicin concentrations, no infectious complications developed. Correlations were made between the pathologic state of the tissue and the tissue gentamicin concentrations. Correlations were also made with tissue gentamicin concentrations and the time after the antibiotic dose to the time of sampling.

The covalent structure of apolipoprotein A-I from canine high density lipoproteins

The complete amino acid sequence of apolipoprotein A-I (apo-A-I) from canine serum high density lipoproteins (HLD) has been determined by automated Edman degradation of the intact protein and proteolytic fragments derived therefrom. The major strategy involved analysis of overlapping sets of peptides generated by cleavage at lysyl residues with Myxobacter protease and by tryptic hydrolysis at arginines in the citraconylated protein derivative. Canine apo-A-I has 232 residues in its single polypeptide chain and its covalent structure is highly homologous to one of the two reported sequences for human apo-A-I. As in the case for the human apoprotein, predictive analysis of the canine apo-A-I sequence suggests that it comprises a series of amphiphilic alpha helices punctuated by a periodic array of prolyl residues. Human HDL contains a second major protein component, apolipoprotein A-II (apo-A-II) that is lacking in HDL from dog serum. The absence of apo-A-II in canine HDL raised the possibility that the apo-A-I from this source might contain within its primary structure sequences related to apo-A-II and thus perform the dual function of both proteins in one. Our analysis proves that canine apo-A-I has all of the structural features of human apo-A-I and that it is not an A-I: A-II hybrid molecule.

Disposition of the diastereoisomer of mefloquine in mice

The disposition of the diastereoisomer of mefloquine, WR 177,602 . HCl, was examined over a 168-hour period after 10 mg/kg of the 14C-labeled drug was administered orally to female albino ICR mice. This drug was absorbed readily. 2 h after dosing, the drug was distributed throughout the animal body with a large percent of the administered dose found in the eyes, submaxillary salivary glands, lungs, spleen, liver, gallbladder plus bile, kidney and carcasses. The elimination half-life of the unmetabolized WR 177,602 in plasma was estimated to be 16.1 h. The major route of excretion of the drug was via the feces (70%), with 23% in the urine 168 h. The elimination half-lives of the unmetabolized drug in urine and feces were 8.0 and 6.9 h, respectively. The disposition of WR 177,602 . HCl was similar to its erythrodiastereoisomer in female mice.

Sequence of the N-terminal half of Bacillus amyloliquefaciens alpha-amylase

Bacillus amyloliquefaciens alpha-amylase (1,4-alpha-D-glucan glucanohydrolase. EC 3.2.1.1), which is commercially supplied as 'Bacillus subtilis alpha-amylase' does not cross-react immunologically with B. subtilis alpha-amylase. This enzyme (from B. amyloliquefaciens) was cleaved by treatment with CNBr into seven fragments. Peptide A was selected for sequence determination. It is the longest one, containing 185 amino acids (i.e. approx. 50% of the total molecule) and connects to the hexapeptide of the N-terminus. Its primary structure was aligned by use of various proteolytic enzymes. The sequence of amino acids 181-184 is identical with that of amino acids 14-17 of the alpha-amylase isolated from B. subtilis (except that amino acid 183 is asparagine rather than aspartic acid).