Interleukin-1 beta (IL-1 beta) levels in gingival crevicular fluid from adults with previous evidence of destructive periodontitis. A cross sectional study

We have estimated the levels of Interleukin-1 beta (IL-1 beta) by ELISA in gingival crevicular fluid (GCF) at 58 sites from 37 patients with adult periodontitis. GCF was collected for 5 s on filter papers and a 2nd sample was collected for 30 s 1 min later. 68/116 strips yielded detectable levels of IL-1 beta. IL-1 beta was present in both the 1st and 2nd samples at 28 sites, in the 1st only at 4 sites and in the 2nd only at 8 sites; 18 sites were below the level of detection for the assay. When the concentrations of IL-1 beta were calculated in the original volume of GCF on each strip, the mean value for positive strips was 34.16 +/- 29.45 (SD) pg/microliters with a range from 1.75 to 97.13 pg/microliters. There were no statistically significant correlations with the plaque index, bleeding index or probable crevice depth (pocket depth). The results indicate that IL-1 is present in the GCF from a proportion of sites with evidence of previous periodontal destruction.

Age and gender effects on ondansetron pharmacokinetics: evaluation of healthy aged volunteers

Modest differences in the clearance of the 5HT3 antagonist, ondansetron, among different age groups were detected in two groups of healthy elderly volunteers, one group aged 61 to 74 years ("elderly") and the other 75 to 82 ("aged") years, in addition to young healthy subjects. Both a single 0.15 mg/kg intravenous dose and a single 8 mg oral dose were administered according to a randomized crossover design with a minimum 3-day washout period between treatments. Mean plasma clearance decreased (young, 0.349 L/hr/kg; elderly, 0.279 L/hr/kg; aged, 0.214 L/hr/kg; p less than 0.05) with increasing age. Volume of distribution at steady state was unaffected by age (young, 1.81 L/kg; elderly, 1.94 L/kg; aged, 1.71 L/kg), resulting in increases in mean plasma half-life (young, 3.4 hours; elderly, 4.5 hours; aged, 5.4 hours) and mean absolute bioavailability (young, 57%; elderly, 61%; aged, 69%) with increasing age. Female subjects cleared ondansetron more slowly than males (p less than 0.05), resulting in higher absolute bioavailability. Ondansetron was well tolerated by all age groups with no increase in the number of adverse events observed in older volunteers.

Pharmacokinetics of cefuroxime axetil and cefaclor: relationship of concentrations in serum to MICs for common respiratory pathogens

The pharmacokinetics of single doses of cefaclor at 250 and 375 mg and cefuroxime axetil at 250 mg administered under optimal conditions (i.e., cefuroxime axetil after food and cefaclor in the fasted state) were studied in 24 healthy male volunteers. Drug concentrations in serum were related to MICs for common respiratory tract pathogens by using data generated from a recently completed national survey. The time the concentrations in serum exceeded the MICs for Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella (formerly Branhamella) catarrhalis were significantly greater (P less than 0.05) for cefuroxime axetil at 250 mg than for cefaclor at 250 or 375 mg. With the recommended dosing regimens (cefuroxime axetil at 250 mg and cefaclor at 375 mg twice daily or cefaclor at 250 mg three times daily), cefuroxime concentrations exceed the MIC for 90% of the strains tested for a greater time period than cefaclor concentrations with either regimen. The reasons for this difference are (i) the greater potency and slower clearance of cefuroxime compared with those of cefaclor and (ii) the greater sensitivity of these pathogens to cefuroxime.

Albuterol extended-release products: effect of food on the pharmacokinetics of single oral doses of Volmax and Proventil Repetabs in healthy male volunteers

The absorption of albuterol from a single 4-mg oral dose of Volmax and Proventil Repetabs was investigated under both fasting and fed conditions in an open-label, randomized, four-period, crossover study in 24 healthy male volunteers. Blood was collected for determination of albuterol plasma concentrations by HPLC over 30 hours postdose. Twenty subjects were evaluable for data analysis. The mean Cmax for Volmax; administered after a meal was 19% lower than that of the drug administered in a fasting state (3.9 ng/mL vs. 4.8 ng/mL; P less than .01). An almost equivalent lowering of the mean Cmax (by 21%) was observed for Proventil Repetabs after administration with a meal versus fasting (4.2 ng/mL vs. 5.3 ng/mL; P less than .01). There were no significant differences between the two formulations in the degree of Cmax reduction due to the presence of food. The tmax occurred significantly later during the fed treatment for Volmax only (4.9 hours fasted vs. 6.4 hours fed; P less than .01). The lag time was significantly greater during the fed treatments for Volmax. No differences were observed in the area under the plasma concentration-time curve (AUC) for either formulation under fasting versus fed conditions, suggesting that the extent of absortion was not altered by food. Overall, food caused a more sustained release of albuterol from both Volmax and Proventil Repetabs.

Regulation of the segmentation gene fushi tarazu has been functionally conserved in Drosophila

An evolutionary approach was applied to identify elements involved in the regulation of the segmentation gene fushi tarazu (ftz) by comparing the Drosophila melanogaster ftz gene with its Drosophila hydei homologue. The overall organization of the ftz gene is very similar in both species. Surprisingly, ftz proved to be inverted in the ANT-C of D. hydei with respect to D. melanogaster. Strong homologies extend over the entire 6 kb of the ftz upstream region with the best match in the 'upstream element'. We identified several highly conserved boxes embedded in unrelated sequences that correspond extremely well to two germ layer specific enhancers in the upstream element. Transformation experiments revealed that D. hydei ftz gene products can restore D. melanogaster ftz function and, furthermore, that trans-acting factors from D. melanogaster recognize and control D. hydei ftz regulatory elements. These findings indicate a conservation of the entire regulatory network among segmentation genes for several millions of years during the evolution of Drosophila.

Kinetic effects of multiple oral doses of acetaminophen on a single oral dose of lamotrigine

In this double-blind, randomized, crossover, placebo-controlled study, the effect of multiple oral doses of acetaminophen on lamotrigine disposition was examined in healthy volunteers. Eight volunteers received two single 300 mg oral doses of lamotrigine, administered 20 days apart. Acetaminophen (2.7 gm/day) or placebo was taken for 24 hours before and continued for 10 days after each lamotrigine dose. Area under the plasma concentration-time curve for lamotrigine [AUC(O-infinity)] and lamotrigine half-life were statistically decreased by 20% (229.0 +/- 62.5 micrograms.hr/ml versus 191.2 +/- 42.1 micrograms.hr/ml, p less than 0.01) and 15% (35.7 +/- 9.3 hours versus 30.2 +/- 7.3 hours, p less than 0.01), respectively, when concurrently administered with acetaminophen. There was no significant difference in the peak plasma concentration or the time to reach peak plasma concentration. The percentage of the dose of lamotrigine recovered in the urine (total) was significantly higher during the acetaminophen treatment (65.9% +/- 12.3% versus 72.5% +/- 5.7%, p = 0.048). Acetaminophen seems to facilitate lamotrigine removal through a yet to be determined mechanism(s).

Absolute bioavailability of phenytoin after 3-phosphoryloxymethyl phenytoin disodium (ACC-9653) administration to humans

3-Phosphoryloxymethyl phenytoin disodium (ACC-9653) is a water-soluble investigational phenytoin (PHT) prodrug for parenteral administration. The objectives of this investigation were to determine the absolute bioavailability and free fraction of PHT after intravenous (i.v.) administration of ACC-9653. Twelve healthy male volunteers received PHT sodium (250 mg/5 ml; 229.95 mg free acid) and ACC-9653 (375 mg/5 ml; 232.87 mg free acid) i.v. in 30 min in a randomized, double-blind cross-over fashion. The conversion half-life (t 1/2) of ACC-9653 to PHT was 9.3 +/- 2.7 min. ACC-9653 was not detected in urine and greater than 99% of ACC-9653 was converted to PHT. The PHT area under the curve (AUC) was not statistically different between treatments; the bioavailability of PHT after ACC-9653 was 99 +/- 11%. The fraction of unbound converted PHT at the end of the prodrug infusion, in the presence of 44 micrograms/ml ACC-9653, was significantly higher than at 180 min, when the concentration of ACC-9653 was 0.1 microgram/ml. ACC-9653 was shown to be a bioequivalent PHT prodrug exhibiting less irritation at the injection site than the current marketed PHT.

Multiskilled health practitioners. Applications to group practice

Multiskilled health practitioners (MSHPs) may be used to reduce costs and increase the availability of services for group practices. There are a variety of possible competency combinations for MSHPs, many of which are unique to the needs of specific health care facilities. Examples of MSHPs as well as employer and employee perceptions of multiskilled needs relevant to health care delivery and applications to the group practice setting are presented.

Ceranapril (SQ 29,852), an orally active inhibitor of angiotensin converting enzyme (ACE)

Ceranapril (SQ 29,852) is a new inhibitor of angiotensin I (AI) converting enzyme (ACE) belonging to the hydroxylphosphonate class. The purpose of the present report is to present the in vivo pharmacology of ceranapril in conscious animal models. In conscious, normotensive rats, ceranapril administered i.v. (ED50 = 63 nmol/kg) or p.o. (ED50 = 530 nmol/kg) inhibited an AI pressor response with potency equal to that of captopril. However, in conscious dogs, ceranapril was a relatively poor inhibitor of the AI pressor response after both i.v. (ED50 = 300 nmol/kg) and p.o. (ED50 = 18 mumol/kg) administration; in monkeys ceranapril was a good inhibitor of the AI pressor response after i.v. (ED50 = 60 nmol/kg) but not p.o. (ED50 = 18 mumol/kg) administration. In rats, the duration of ceranapril's inhibition of an AI pressor response was longer than an equimolar dose of captopril. Similarly, in SHR, ceranapril's blood pressure lowering effect had a longer duration than that of captopril. Ceranapril's ACE inhibitory effects were longer lasting in anephric rats than in sham rats, suggesting a renal route of excretion for ceranapril. Ceranapril administration to conscious female dogs resulted in significant increases in renal plasma flow and GFR. In SHR, doses of 23 and 68 mumol/kg resulted in significant blood pressure lowering that lasted 24 h. Oral doses of 2.3, 6.8, 23, and 68 mumol/kg in two-kidney, one-clip hypertensive rats resulted in significant and dose-related falls in arterial pressure, which again persisted for 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood pressure lowering and renal hemodynamic effects of fosinopril in conscious animal models

The blood pressure lowering and renal hemodynamic effects of fosinopril, the chemically novel inhibitor of angiotensin I converting enzyme (ACE), was assessed in conscious animal models. In conscious dogs, intravenous infusion of SQ 27,519 [0.5 mg/kg (1.1 mumol/kg) bolus plus 0.1 mg/kg/min (0.22 mumol/kg/min)], the active moiety of the prodrug fosinopril, increased PAH clearance and GFR by 25 and 16%, respectively (p less than 0.05, each) without changing arterial pressure (AP). Urine volume, sodium excretion, and potassium excretion were elevated, although not significantly increased. In sodium-depleted cynomolgus monkeys, 1.5 and 5.0 mumol/kg (0.88 and 2.9 mg/kg) p.o. of fosinopril lowered arterial pressure from 115 +/- 5 to 99 +/- 5 mm Hg and from 116 +/- 3 to 87 +/- 4 mmHg, respectively (p less than 0.05, each). When given orally to SHR at 10 and 30 mg/kg (5.9 and 17.6 mumol/kg), fosinopril lowered AP by 23 (183 +/- 4 to 160 +/- 5 mm Hg) and 20 mm Hg (176 +/- 4 to 156 +/- 4 mm Hg), respectively. The combination of fosinopril [10 mg/kg (5.9 mumol/kg)] plus hydrochlorothiazide (10 mg/kg) reduced AP from 206 +/- 4 to 167 +/- 2 mm Hg when given orally to SHR. Fosinopril was more effective in two-kidney, one-clip hypertensive rats relative to SHR; AP fell from 201 +/- 9 to 160 +/- 7 mm Hg after 10 mg/kg (5.9 mumol/kg), and from 205 +/- 7 to 145 +/- 7 mm Hg after 30 mg/kg (17.6 mumol/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

The TEACL method of DNA-DNA hybridization: technical considerations

This paper emanated from a conference concerning the value, accuracy, and technical considerations of DNA-DNA hybridization for evolutionary studies. Our laboratory has been performing the so-called TEACL (tetraethylammonium chloride) method, and we have amassed sufficient data to indicate that this method is very powerful if performed properly with correct analyses. Here we address five technical considerations: (1) We present empirical data that size correction for tracer length is legitimate and accurate. (2) We show that the error of delta Tm measurement does not significantly increase with increasing distance up to at least 10 degrees C. (3) The error distribution for delta Tm does not deviate from the expected normal distribution indicating parametric statistics are probably legitimate for analyses. (4) Using a known phylogeny we examined the resolving power of the technique by showing that at least five taxa can be correctly placed in phylogenies with a maximum delta Tm of 2.5 degrees C. (5) To date, all our data sets based on DNA-DNA hybridization are very robust with respect to analytical procedures in that every algorithm used on the data sets has yielded identical trees with nearly identical branch lengths. Nevertheless, we point out that theoretical analyses of distance data (as generated by DNA-DNA hybridization) are lacking, especially with regard to tests of the molecular clock hypothesis.

Extreme rates and heterogeneity in insect DNA evolution

DNA-DNA hybridization studies of insects, more specifically Drosophila and cave crickets, have revealed interesting patterns of genome evolution that contrast markedly with what has been seen in other taxa, especially mammals and birds. Insect genomes are composed of sections of single-copy DNA with extreme variation in rates of evolutionary change. This variation is more extreme than between introns and exons; introns fall into the relatively conserved fraction of the genome. Attempts to calculate absolute rates of change in Drosophila DNA have all led to estimates some 5-10 times faster than those found in most vertebrates; this is true even for the more conservative part of the nuclear genome. Finally we point out that morphological similarity, chromosomal similarity, and/or ability to form interspecific hybrids is often associated with quite high levels of single-copy DNA divergence in insects as compared to mammals and birds.

Determination of albuterol concentrations in human plasma using solid-phase extraction and high-performance liquid chromatography with fluorescence detection

A fast, simple, and accurate method for determining albuterol concentrations in human plasma has been developed and validated for use in routine clinical analyses. This method involves a solid-phase extraction procedure using silica cartridges and normal-phase high-performance liquid chromatography with fluorescence detection. Regression analysis showed the method was linear over the standard curve range 1-16 ng ml-1. The percent recovery for albuterol and the internal standard, bamethane, at 5 ng ml-1 was found to be greater than 90%. The newly developed method has been applied in the analysis of plasma samples from patients and healthy volunteers.

Fosinopril, a phosphinic acid inhibitor of angiotensin I converting enzyme: in vitro and preclinical in vivo pharmacology

Fosinopril is the first member of a new chemical class of angiotensin I (AI) converting enzyme (ACE) inhibitors, the phosphinic acids. In vitro, SQ 27,519, the active moiety of the prodrug fosinopril, was a more potent inhibitor of purified rabbit lung ACE- (IC50 = 11 vs. 23 nM) and bradykinin-induced contractions of guinea pig ileum than captopril. In vivo, SQ 27,519 was equipotent to captopril as an inhibitor of an AI pressor response after intravenous (i.v.) administration to conscious rats and monkeys but appeared to be less potent in conscious dogs. After oral administration, fosinopril again was equipotent to captopril as an inhibitor of an AI pressor response in rats and monkeys and slightly less potent in dogs. However, both SQ 27,519 (i.v. studies) and fosinopril (oral studies) had a longer effect than captopril in all three species. When fosinopril was administered orally for 5 days, its effects on an AI pressor response were the same on days 1 and 5, suggesting lack of tolerance to the compound. The ACE inhibitory effect of captopril, but not fosinopril, was prolonged in conscious rats with glycerol-induced acute renal failure, suggesting that fosinopril is excreted by an extrarenal route. Finally, fosinopril had no effect on the pressor or chronotropic effects of norepinephrine (NE) or 1,1-dimethyl-4-phenylpiperinium (DMPP) or electrical stimulation of the sympathetic ganglia of pithed rats. Fosinopril attenuated the pressor, but not the chronotropic effects of tyramine. We conclude that fosinopril is a potent and long-lasting inhibitor of ACE in conscious animal models that does not impair adrenergic function or reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of altering small bowel transit time on sustained release theophylline absorption

The relationship between variations in small bowel transit time (SBTT) and the absorption of theophylline from a sustained-release product was evaluated in a three-way, randomized, crossover study in 12 healthy male nonsmokers. Subjects received sustained-release theophylline (600 mg) with loperamide (8 mg every 6 hour x 8 doses). metoclopramide (15 mg every 6 hour x 8 doses) or placebo (every 6 hour x 8 doses). Theophylline solution (400 mg) was used as a reference standard. Serum samples were collected periodically for 72 hours for theophylline concentration determinations. SBTT was measured by the lactulose hydrogen breath test. Compared with placebo (98 +/- 53 min), SBTT was increased with loperamide (211 +/- 87 min; P less than 0.001) and decreased with metoclopramide (55 +/- 18 min; P less than 0.001). Loperamide decreased the rate, but not the extent of theophylline absorption from this product. This was evident from the reduced Cmax, the prolonged Tmax, and the decreased fraction of the dose absorbed at 24 hours, while the area under the curves remained the same. In contrast, metoclopramide had no effect either on rate or extent of absorption. The data suggest that the effect of loperamide on these absorption parameters was due to an increase in the dissolution time of this sustained-release product.

Effect of metoclopramide, bethanechol, and loperamide on gastric residence time, gastric emptying, and mouth-to-cecum transit time

The effects of metoclopramide, bethanechol, and loperamide on the gastric residence time (GRT), gastric emptying (GE), and mouth-to-cecum transit time (MCTT) of a solution were investigated in three separate studies of five healthy male volunteers each. Metoclopramide in doses of 5, 10, and 15 mg prolonged GRT by 33, 88, and 162%, respectively, almost reaching statistical significance (p 0.058). A relationship was observed between GRT prolongation, and metoclopramide area under the plasma-time curve (p 0.01) and metoclopramide observed time to maximum concentration (p 0.01). Metoclopramide had an inconsistent effect on MCTT. Bethanechol 50 mg prolonged GRT by 64% (p 0.031) and had no effect on MCTT. Loperamide at doses of 2 and 8 mg prolonged GRT by 18 and 115% (p 0.043) and MCTT by 30 and 130% (p 0.0001), respectively. None of these motility-altering agents affected GE.

Preclinical pharmacology of zofenopril, an inhibitor of angiotensin I converting enzyme

Zofenopril calcium (one-half calcium salt) is a prodrug ester analog of captopril whose biological effects are manifested by its active component, SQ 26,333. Because of the relative insolubilities of both zofenopril calcium and SQ 26,333, zofenopril potassium salt and SQ 26,703, the arginine salt of the active ACE (angiotensin I converting enzyme) inhibitory moiety of zofenopril, were employed in many of the following studies. The in vitro and in vivo pharmacological effects of zofenopril have been evaluated and comparisons have been made to captopril. In vitro, SQ 26,703 was more potent than captopril as an inhibitor of rabbit lung ACE (IC50 = 8 vs. 23 nM). SQ 26,703 was also a potent inhibitor of angiotensin I (AI)-induced contractions (EC50 = 3 nM) and a potentiator of bradykinin-induced contractions (EC50 = 1 nM) of isolated guinea pig ileum, while it had no effect on the inotropic effects of angiotensin II, BaCl2, PGE1, histamine, serotonin, or acetycholine in the same tissue, signifying that zofenopril is a specific inhibitor of ACE. In vivo, the potency of SQ 26,703 was equal to or greater than that of captopril as an inhibitor of an AI pressor response when given intravenously to rats, dogs, and monkeys. After oral administration of equimolar doses, zofenopril was the more effective and longer lasting ACE inhibitor in all three species. In SHR, doses of 6.6 and 22.0 mg/kg, p.o. lowered pressure by 20 and 33 mm Hg, respectively, while 30 mg/kg of captopril lowered pressure by 25 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol suppresses endothelium-dependent relaxation in rat mesenteric vascular beds

The effects of prolonged infusions of ethanol on endothelium-dependent vasorelaxation induced by acetylcholine and adenosine triphosphate (ATP) and on endothelium-independent relaxation induced by papaverine were studied and compared in isolated perfused rat mesenteric artery preparations. Infusion of ethanol over 60 minutes at concentrations of 1.6, 4.7, 6.3, and 7.9 mg/ml caused concentration-related inhibition of norepinephrine-induced vasoconstriction. In preparations infused with 6.3 and 7.9 mg/ml, this effect reached a maximum after 10-20 minutes but had vanished by the end of the infusion; 1 hour after the end of the infusion, the effects of norepinephrine were potentiated by 71% and 108%, respectively. Acetylcholine-induced vasorelaxation (EC50 3.0 ng/ml in controls) was significantly reduced after 6.3 mg/ml ethanol infusion and totally abolished after 7.9 mg/ml ethanol infusion. ATP-induced vasorelaxation (EC50 180 ng/ml in controls) was also abolished after 7.9 mg/ml of ethanol infusion. By contrast, the vasorelaxant effects of papaverine were not affected by 7.9 mg/ml ethanol infusion. Light-microscopic examination revealed that the endothelial cells were present in ethanol-treated and in control mesenteric arterial beds. These observations indicate that ethanol suppresses endothelium-dependent vasorelaxation without apparent removal of the endothelial cells. The compromised relaxant capacity of the endothelium after ethanol and the resultant intensification of the vasoconstrictor response to norepinephrine may contribute to the development of vascular diseases such as hypertension and stroke.

Influence of rifampin on tocainide pharmacokinetics in humans

The effects of metabolic enzyme induction by rifampin on the pharmacokinetics of tocainide were studied in eight healthy volunteers. In an open, unrandomized fashion, volunteers received tocainide hydrochloride 600 mg orally. Blood samples were obtained immediately before and at various time intervals up to 48 hours after the dose. Urine samples were collected before and at various intervals up to 72 hours after the dose. Serum and urine samples were assayed for tocainide content by high-performance liquid chromatography. After a four-week washout period, volunteers ingested 300 mg of rifampin by mouth every 12 hours. After 10 doses, subjects received a second oral dose of tocainide hydrochloride 600 mg, and blood and urine samples were collected as before. During the sampling period, subjects continued to ingest rifampin 300 mg orally every 12 hours. Significant differences in elimination rate constant (average increase, 0.0545 to 0.0748 hr-1), elimination half-life (average reduction, 13.2 to 9.4 hours), oral clearance, and area under the concentration-time curve (average reduction, 76.8 to 55.0 mg.hr/L) between the control and rifampin treatment phases were observed. Volume of distribution and renal clearance of tocainide were not significantly different after rifampin treatment. Tocainide appears to be susceptible to significant drug-drug interactions mediated by metabolic enzyme induction.

Intraspecific and interspecific genetic variation in Drosophila

Utilizing the technique of DNA-DNA hybridization, we have characterized the degree of genetic variability in single-copy DNA both within and between several species of Drosophila. The results of intraspecific variation studies indicate considerable variation both for levels of nucleotide heterozygosity (estimated to be over 2%) as well as for insertions-deletions. Interspecific studies confirm this great deal of variability and further establish an extreme heterogeneity within Drosophila genomes for rates of divergence. This heterogeneity is much more extreme than that seen between exons and introns. The degree of single-copy DNA divergence generally supports phylogenetic affinities deduced from more traditional methods. However, exceptions occur where single-copy DNA divergence is not correlated with other properties such as degree of chromosomal differentiation, morphology, or ability to form interspecific hybrids. We argue that single-copy DNA divergence as measured by DNA-DNA hybridization is an accurate indicator of phylogenetic relationships and therefore sheds light on the evolution of other biological properties. Many, if not most, evolutionary tests require an accurate phylogeny of the group being studied and DNA, because of the high information content inherent within the molecule, offers the best hope of deriving true phylogenies.

Angiotensin-converting enzyme inhibitors. Mercaptan, carboxyalkyl dipeptide, and phosphinic acid inhibitors incorporating 4-substituted prolines

Analogues of captopril, enalaprilat, and the phosphinic acid [hydroxy(4-phenylbutyl)phosphinyl]acetyl]-L-proline incorporating 4-substituted proline derivatives have been synthesized and evaluated as inhibitors of angiotensin-converting enzyme (ACE) in vitro and in vivo. The 4-substituted prolines, incorporating alkyl, aryl, alkoxy, aryloxy, alkylthio, and arylthio substituents were prepared from derivatives of 4-hydroxy- and 4-ketoproline. In general, analogues of all three classes of inhibitors with hydrophobic substituents on proline were more potent in vitro than the corresponding unsubstituted proline compounds. 4-Substituted analogues of captopril showed greater potency and duration of action than the parent compound as inhibitors of the angiotensin I induced pressor response in normotensive rats. The S-benzoyl derivative of cis-4-(phenylthio)captopril, zofenopril, was found to be one of the most potent compounds of this class and is now being evaluated clinically as an antihypertensive agent. In the phosphinic acid series, the 4-ethylenethioketal and trans-4-cyclohexyl derivatives were found to be the most potent compounds in vitro and in vivo. A prodrug of the latter compound, fosinopril, is also being evaluated in clinical trials.

Accuracy of tobramycin delivery by four i.v. infusion methods

The accuracy of tobramycin delivery by four methods of intermittent intravenous infusion was studied in 11 healthy male volunteers. Subjects received intravenous tobramycin (as the sulfate salt) 1.5 mg/kg by each of four infusion methods in a nonblinded, randomized, four-way crossover design. The methods used for intravenous infusion were (1) minibag via gravity flow (MG), (2) minibag with the secondary infusion tubing inserted below a volumetric infusion pump (MP), (3) metered chamber via volumetric infusion pump (MC), and (4) syringe pump (SP). Doses were diluted to a volume of 50 mL, except for the two minibag methods, for which the dilution was necessarily greater because of manufacturer overfill. Intravenous flow rates for both primary fluid and drug administration were set at 100 mL/hr, and the duration of drug infusion was documented by observation for each administered dose. The fluid volume of 12 minibags was measured to assess manufacturer overfill. Fluid remaining in the secondary i.v. tubing for the minibag methods was collected after the infusion. Seventeen blood samples were obtained before and at various time intervals after each dose and analyzed in duplicate for tobramycin content by fluorescence polarization immunoassay. A mean of 10% of each dose remained in the secondary i.v. tubing at the completion of the infusion for the minibag methods, whereas less than 1% of each dose remained in the secondary tubing for the SP method.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of four intravenous infusion methods on tobramycin pharmacokinetics

The influence of four intermittent intravenous infusion methods on the determination of tobramycin pharmacokinetic values and predicted doses was evaluated in 11 healthy adult volunteers. Each subject received tobramycin (as the sulfate salt) 1.5 mg/kg by each of four i.v. infusion methods: (1) minibag via gravity flow (MG), (2) minibag with the secondary infusion tubing inserted below a volumetric pump (MP), (3) metered chamber via volumetric pump (MC), and (4) syringe pump (SP). Infusion rates were initially set to administer each dose over a 30-minute period. Sixteen blood samples were obtained over an eight-hour period before and at various time intervals after each dose and were analyzed for tobramycin content by fluorescence polarization immunoassay. Area under the serum concentration-time curve from time zero to infinity (AUC0-infinity) was calculated by the trapezoidal rule. Serum tobramycin concentration data for each subject were fitted to a biexponential decay model with zero-order input. beta and V beta were calculated from fitted data. One-compartment pharmacokinetic values, elimination rate constant (kappa), apparent volume of distribution (V), and predicted doses to achieve steady-state peak concentrations of 6 micrograms/mL were calculated by the method of Sawchuk and Zaske. There were no significant differences in either beta or kappa among the infusion methods. V beta values (mean +/- S.D.) for the methods were 0.240 +/- 0.025 (MG), 0.257 +/- 0.025 (MP), 0.221 +/- 0.027 (MC), and 0.231 +/- 0.032 (SP) L/kg.(ABSTRACT TRUNCATED AT 250 WORDS)

Calibration of the change in thermal stability of DNA duplexes and degree of base pair mismatch

One method of determining the degree of base pair divergence between two sources of DNA (different strains, species, etc.) is to determine the decrease in thermal stability of hybrid duplex DNA due to mismatching of base pairs. Attempts to calibrate the change in median melting temperature (delta Tm) to base pair mismatch have led to conflicting results. We have studied the delta Tm between DNAs of known sequence over a range of from 0.55% to 7.2% base pair mismatch. The relationship of delta Tm and percent base pair mismatch is remarkably linear over this range with a correlation coefficient greater than 0.98. A delta Tm of 1 degree C corresponds to 1.7% base pair mismatch. This conversion is higher than that usually assumed and, therefore, rates of DNA evolution estimated by DNA-DNA hybridization studies are likely faster than previously thought.

Rates and patterns of scnDNA and mtDNA divergence within the Drosophila melanogaster subgroup

Levels of DNA divergence among the eight species of the Drosophila melanogaster subgroup and D. takahashii have been determined using the technique of DNA-DNA hybridization. Two types of DNA were used: single-copy nuclear DNA (scnDNA) and mitochondrial DNA (mtDNA). The major findings are: (1) A phylogeny has been derived for the group based on scnDNA which is congruent with chromosomal data, morphology, and behavior. The three homosequential species, simulans, sechellia, and mauritiana, are very closely related; the scnDNA divergence indicate the two island species are a monophyletic group. (2) The rates of change of scnDNA and mtDNA are not greatly different; if anything scnDNA evolves faster than mtDNA. (3) The rates of scnDNA evolution are not closely correlated to chromosomal (inversion) evolution. (4) The Drosophila genome appears to consist of two distinct classes of scnDNA with respect to rate of evolutionary change, a very rapidly evolving fraction and a relatively conservative fraction. (5) The absolute rate of change was estimated to be at least 1.7% nucleotide substitution per one million years. (6) DNA distance estimates based on restriction site variation are correlated with distances based on DNA-DNA hybridization, although the correlation is not very strong.

The effect of cimetidine dose timing on oral propranolol kinetics in adults

Ten healthy male volunteers completed a study to determine the effect of cimetidine dose timing on the oral clearance of propranolol. Propranolol HCl 160 mg as tablets, was administered daily at 8 AM for 4 consecutive days on three occasions. In addition, cimetidine HCl 800 mg as tablets, was administered either simultaneously in the morning with propranolol (8 AM), at bedtime (10 PM), or not at all (control). Each treatment was separated by at least a 3-day washout. Propranolol and cimetidine serum samples were measured over the 24-hour dosing interval after the last propranolol dose. Cimetidine administration at 8 AM and 10 PM was associated with significant mean increases in the propranolol area under the serum concentration-time curve of 26% and 41%, respectively (P less than .002). The mean elimination half-life of propranolol was 6.3 hours during all three treatments. There was no significant difference in area under cimetidine serum concentration time curve between 8 AM and 10 PM dosing. Dosing cimetidine at bedtime 10 hours before propranolol does not diminish the magnitude of interaction.

Pressor responses induced by Bay K 8644 involve both release of adrenal catecholamines and calcium channel activation

1. The dihydropyridine calcium channel activator, Bay K 8644, is believed to increase mean arterial blood pressure in several animal models, as a result of direct activation of vascular smooth muscle cells by increasing calcium influx through the voltage-dependent calcium channels. The purpose of the current study was to elucidate further the mechanism of action of Bay K 8644, by examining the possibility that the pressor response to Bay K 8644 may also be the result of indirect activation of the vascular smooth muscle cells by release of adrenal catecholamines. 2. Intravenous administration of Bay K 8644 increased mean arterial pressure in a dose-dependent manner in conscious, normotensive rats. This pressor response was blocked by calcium channel blockers (nifedipine, verapamil, and diltiazem) at doses lower than were necessary to decrease resting mean arterial pressure. 3. alpha-Adrenoceptor antagonists (phentolamine, yohimbine, and prazosin) completely blocked the Bay K 8644-induced pressor responses and converted them to depressor responses. Adrenalectomy did not alter the inhibitory effect of phentolamine on the pressor response to Bay K 8644. However, adrenalectomy or adrenal demedullectomy prevented the phentolamine-induced reversal of the Bay K 8644 pressor response to a depressor response. In addition, adrenalectomy did not affect the ability of phentolamine to reverse the pressor response to exogenous adrenaline administration to a depressor response. 4. These data suggest that the pressor response to Bay K 8644 may involve both direct activation of vascular smooth muscle cells and indirect activation of the muscle cells by release of adrenal catecholamines.

(Phosphinyloxy)acyl amino acid inhibitors of angiotensin converting enzyme (ACE). 1. Discovery of (S)-1-[6-amino-2-[[hydroxy(4-phenylbutyl)phosphinyl]oxy]-1-oxohexyl]-L -proline a novel orally active inhibitor of ACE

The synthesis of a series of orally active, phosphinyloxyacyl proline inhibitors of angiotensin converting enzyme (ACE) is described. The in vitro and in vivo ACE inhibitory activities are reported for each compound. The structure-activity relationship for this series of compounds in relation to the carboxyalkyl dipeptide ACE inhibitors as well as other types of hydroxyphosphinyl-containing ACE inhibitors (e.g., the corresponding nitrogen and carbon isosteres) is discussed. Within an isosteric series of phosphorus-containing inhibitors based on the lysylproline terminal dipeptide sequence, only the phosphonates (oxygen isosteres) show a high level of oral activity. Optimum potency and oral activity in the phosphonate series occurs with the (phenylbutyl)- and n-hexylphosphonate side chains. An aminobutyl side chain in the P1' residue is an absolute requirement for full expression of oral activity. The most potent of these compounds, 8b (SQ 29,852), has intravenous and oral activities superior in potency to those of captopril in the normotensive rat.

Simultaneous objective and subjective evaluation of meclofenamate sodium in the treatment of primary dysmenorrhea

Eighteen patients participated in a double-blind, placebo-controlled, single-dose, crossover study of meclofenamate sodium in women with primary dysmenorrhea. Simultaneous evaluations of pain intensity and pain relief, sampling of continuous intrauterine pressure recording, and monitoring of blood meclofenamate levels were carried out. Improvements in pain intensity and pain relief were observed at 45 minutes and reached statistical significance at and beyond 1 hour 45 minutes after meclofenamate therapy. Ten of 14 uterine pressure parameters showed statistically significant responses after drug therapy and 12 of the 14 parameters showed statistically significant differences in time-response patterns. Statistically significant changes were noted as early as 45 minutes after meclofenamate therapy. Statistically significant correlations were found between and among the parameters of blood drug level and the subjective and objective measures. No drug-related adverse effects were found.

Intraspecific DNA divergence in Drosophila: a study on parthenogenetic D. mercatorum

Drosophila mercatorum is a species that can give rise to totally homozygous parthenogenetic strains. Using the technique of DNA-DNA hybridization, we have assessed the overall single-copy DNA differences among three independently derived strains that represent three independent genomes. Among strains, the average difference between homoduplex and heteroduplex median melting temperatures is 1.3 degrees C. This represents greater than or equal to 1.3% base-pair mismatch. Normalized percent of reassociation indicates further genetic differences, probably reflecting insertion/deletion differences and/or regions of the genome that are highly variable. This overall intraspecific genetic variation is higher than generally is thought to exist but is consistent with growing evidence of extensive DNA diversity within species of invertebrates. High intraspecific DNA variation may be correlated with rapid phyletic rates of evolution. Because of this high level of variation, the technique of DNA-DNA hybridization may be used to study intraspecific variation in invertebrates but is limited in its usefulness for higher systematic studies.

Bovine monoclonal antibodies to the F5 (K99) pilus antigen of E. coli, produced by murine/bovine hybridomas

Lymph node cells from calves immunized with purified pilus antigen of K99+ enterotoxigenic E. coli (ETEC) were fused with mouse myeloma (NSO) cells, and with non-Ig producing mouse/calf hybridomas or with a bovine Ig-producing mouse/calf/calf secondary hybridoma. Lines secreting bovine monoclonal IgG1 specific for K99 pilus antigen in an ELISA were obtained in each case. The two lines derived from xenohybridoma fusion partners have been secreting anti-K99 bovine monoclonal antibody for over one year in continual passage. None of the antibodies cross-reacted with other pilus types including K88, CFAI, CFAII, 987P or CP; they all inhibited agglutination of horse RBC (which have a K99 receptor) in the presence of K99 antigen; they showed positive fluorescence in an indirect binding assay on K99+ ETEC and inhibited K99+ ETEC adhesion to piglet enterocytes. These antibodies have potential prophylactic and therapeutic use in control and treatment of diarrhoea.

Substituted 1,2,3,4-tetrahydroaminonaphthols: antihypertensive agents, calcium channel blockers, and adrenergic receptor blockers with catecholamine-depleting effects

Substituted 1,2,3,4-tetrahydroaminonaphthols were found to be calcium channel blockers with antihypertensive properties. These compounds also possessed adrenergic beta-receptor blocking activity. From the structure-activity studies, no clear correlation emerged between the in vitro calcium channel blocking activity and the acute anti-hypertensive activity in cannulated spontaneously hypertensive rats. Extensive pharmacological testing of selected compounds indicated that aminonaphthols are antihypertensive agents with many pharmacological properties. The relative contribution of various pharmacological actions toward the observed antihypertensive activity is unclear. Since the clinically useful calcium channel blocker verapamil is structurally related to these compounds, one of the aminonaphthols, trans-3-[(3,3-diphenylpropyl)amino]-1,2,3,4-tetrahydro-6,7 -dimethoxy-2-naphthalenol (12), was compared with verapamil for calcium channel blocking activity, adrenergic blocking activity, and catecholamine-depleting activity. Both compounds were found to be equipotent in these test systems.

SQ 27,786 and SQ 28,853: two angiotensin converting enzyme inhibitors with potent diuretic activity

SQ 27,786 and SQ 28,853 were designed to possess both angiotensin converting enzyme (ACE) inhibitory and diuretic properties. Both compounds were given to conscious male Sprague-Dawley rats and mongrel female dogs to determine ACE inhibitory and diuretic activities. All animals had previously been equipped with indwelling arterial and venous catheters. Both compounds resulted in dose-related inhibition of an angiotensin I pressor response in rats after i.v. administration. The maximum response and duration of effect of both compounds were similar to that seen with equimolar doses of captopril. Oral doses of SQ 28,853 (50.0 mumol/kg) and SQ 27,786 (15.0 mumol/kg) resulted in 15 and 64% inhibition of ACE, respectively. In conscious normotensive dogs, both compounds (2.0 mg/kg, i.v.) resulted in complete inhibition of ACE. Urine volume was increased by 153 and 667% after SQ 27,786 and SQ 28,853, respectively. Similarly, sodium excretion was increased by 336% after SQ 27,786 and by 650% after SQ 28,853. SQ 27,786 and SQ 28,853 increased potassium excretion by 54 and 115%, respectively. No significant changes in blood pressure were observed with either compound in either species. These results demonstrate that both SQ 27,786 and SQ 28,853 are potent ACE inhibitors and diuretic agents in vivo.

Academic-drug industry fellowships

The UNC/BW fellowship, like other industry/academia collaborative fellowships, provides a unique training experience in clinical research. Both academia and the pharmaceutical industry have opened their doors and allowed clinical pharmacists to spend a year or more developing clinical research skills and an understanding of the drug development process. Is it worth it? Is this program a benefit to the individuals, to the sponsors, or to the profession of pharmacy? The survey of these fellows provides us with the individual's perspective on the benefit and quality of the fellowship. Most believed the fellowship provided them with training to meet their needs and interests. However, given this small number of individual opinions and comments, how do we determine whether the fellowship is meeting the original goal to train clinical pharmacists to be clinical researchers? By looking at the career paths of those who have completed the program, we may gain insight into whether the fellows are involved with research. Since the fellowship has been in existence for only six years, we really can look only at the initial placement of these clinical pharmacists. A majority have gained employment with clinical research responsibilities within the pharmaceutical industry. One measure of the research capabilities of these fellows is their contributions to the scientific literature; 10 papers and 3 abstracts have been generated by fellows since they completed their fellowships (Appendix I). As expected, the research contributions of the two-year fellows are greater than that of the one-year fellows. Seven one-year fellows did not have a publication.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of oral cimetidine on total and unbound serum lidocaine concentrations in patients with suspected myocardial infarction

In this study, we prospectively evaluated the effect of oral cimetidine on serum lidocaine concentrations in 6 patients with suspected myocardial infarction. Compared to baseline lidocaine levels, total lidocaine concentrations increased by 8.2 +/- 7.8% at 6 hours, 16.4 +/- 9.0% at 12 hours and 27.9 +/- 9.4% at 24 hours after two doses of oral cimetidine. Unbound lidocaine concentrations increased by 14.3 +/- 4.1% at 6 hours, and 18.3 +/- 10.3% at 24 hours after cimetidine. In patients with myocardial infarction (3), total lidocaine concentrations increased by 24.2 +/- 10.4%, whereas unbound lidocaine increased by 8.9 +/- 10.2% at 24 hours. Therefore, increases in total lidocaine concentrations after cimetidine administration were considerably less than those previously reported and empiric dosage reductions of lidocaine in patients receiving cimetidine may not be appropriate.

Clinical pharmacology of carvedilol in normal volunteers

The mechanism of the vasodilatory action of carvedilol (BM 14190), a new antihypertensive agent, was investigated in normal volunteers. Intra-arterial blood pressure and ECG were monitored continuously. Carvedilol (1 mg/min for 15 minutes) produced a rapid reduction in blood pressure and a transient increase in heart rate. At the end of infusion, systolic and diastolic blood pressure were reduced by 23% (-32.3 mm Hg) and 18% (-13.6 mm Hg), respectively, whereas heart rate was not different from baseline. At the doses used, the hypotensive effect of carvedilol was greater than that of labetalol (36 and 72 mg in 15 minutes). Carvedilol and labetalol antagonized isoproterenol-induced hypotension and tachycardia, at serum levels greater than or equal to 8 and 20 mg/ml, respectively. Both drugs antagonized phenylephrine pressor effects. A similar degree of inhibition (25% of control) of pressor effects was observed for carvedilol and labetalol when their respective serum concentrations were 23 ng/ml and 80 ng/ml. Neither carvedilol nor labetalol had any effect on AII pressor responses. Carvedilol serum levels as high as 150 ng/ml failed to inhibit AII-induced pressor responses. Our results suggest that at the doses used in this study, carvedilol has both alpha 1-and nonselective beta-receptor blocking properties. Moreover, carvedilol is approximately three to five times more potent than labetalol in blocking alpha 1-and beta-receptors and in reducing blood pressure.

Rates of nucleotide substitution in Drosophila mitochondrial DNA and nuclear DNA are similar

While the majority of DNA in eukaryotes is in the nucleus, a small but functionally significant amount is found in organelles such as chloroplasts and mitochondria. A recent, rather remarkable, finding has been that in vertebrates the DNA in the mitochondria (mtDNA) is evolving 5-10 times faster than the DNA in the nucleus. No similar studies have been done with invertebrates. Using the technique of DNA X DNA hybridization, we have measured the degree of nucleotide substitution between Drosophila melanogaster and Drosophila yakuba for both single-copy nuclear DNA (scnDNA) and mtDNA. The change in melting temperature is the same in both types of DNA hybrids. Thus we conclude that mtDNA and scnDNA are evolving at similar rates in these Drosophila. Considerable DNA sequence data are available for the mtDNAs studied, allowing us to estimate that a 1 degree C change in melting temperature corresponds to a 1.5-2% base-pair mismatch.

Effect of duration of lidocaine infusion and route of cimetidine administration on lidocaine pharmacokinetics

The effects of the duration of lidocaine infusion and the route of cimetidine administration on lidocaine pharmacokinetics were evaluated in a randomized, three-phase crossover study of six healthy men. Lidocaine hydrochloride 100 mg was administered intravenously over two minutes, and plasma lidocaine concentrations were determined before treatment and at various intervals for three hours. Immediately after the three-hour sample was obtained, a second 100-mg dose of lidocaine hydrochloride was given, followed by a 21-hour constant infusion at a rate of 2 mg/min. Plasma lidocaine concentrations were determined at various intervals during the infusion and for eight hours afterward. Urine was collected during the last five hours of the infusion and assayed for lidocaine, monoethylglycinexylidide (MEGX), and glycinexylidide (GX). The following treatments were administered to each subject in a crossover manner: a placebo tablet every six hours, beginning two days before lidocaine administration; cimetidine 300 mg orally every six hours, beginning two days before lidocaine administration; and cimetidine hydrochloride 300 mg i.v. every six hours, beginning one hour before lidocaine administration. Each medication was given until the lidocaine infusion was discontinued. Subjects fasted and remained supine throughout each treatment period. Oral cimetidine increased the area under the concentration-time curve for lidocaine by 14.7% and increased the elimination half-life of lidocaine; i.v. cimetidine did not have a significant effect on lidocaine disposition. Lidocaine clearance was 34% lower under steady-state than single-dose conditions, but the effects of cimetidine on lidocaine disposition were similar under both conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Liquid chromatographic assay and disposition of carvedilol in healthy volunteers

Quantitative determination of serum concentrations of carvedilol [(+/-)-1-(carbazol-4-yloxy)-3-[[2-(o-methoxyphenoxy)ethyl) amino]-2-propanol], a combined alpha- and beta-adrenergic receptor antagonist, was obtained using HPLC with spectrofluorometric detection. Carvedilol was extracted from alkalinized serum with ether and was subsequently back extracted with diluted phosphoric acid. This method proved to be sensitive and reproducible (mean coefficient of variation of 6.1% for 0.25 to 150 nanograms per milliliter of serum). A single dose of carvedilol (5, 10, or 15 mg) was given as an intravenous infusion to three healthy volunteers. Carvedilol serum concentration-time profiles were fitted best to a three-compartment model and the pharmacokinetic data revealed the following mean values: Vdss of 1.97 L/kg, mean residence time (MRT) of 4.66 h, and CL of 0.437 L X h-1 X kg-1.

Cimetidine and carbamazepine: a complex drug interaction

Cimetidine has been shown to inhibit the elimination of carbamazepine after a single oral dose. The mechanism of this interaction is thought to be inhibition of carbamazepine metabolism by the hepatic microsomal enzyme system. Because carbamazepine metabolism undergoes autoinduction with chronic administration, it is not known whether or not the clinical significance of this interaction can be predicted from the results of a single-dose study. The purpose of this study was to evaluate the presence of an interaction under steady-state enzyme-induced conditions. Using an open treatment design, carbamazepine, 300 mg b.i.d., was taken by eight healthy volunteers for 42 days (days 1-42). Cimetidine, 400 mg t.i.d., was taken for 7 days (days 29-35). Steady-state carbamazepine increased 17% after 2 days of cimetidine treatment (from 4.7 +/- 0.8 to 5.5 +/- 1.4 micrograms/ml; p less than 0.05). Six of the eight subjects noted side effects shortly after starting cimetidine treatment. Carbamazepine returned to the pre-cimetidine level and the side effects diminished by the 7th day of cimetidine administration. Therefore, the clinical significance of this interaction appears to be time dependent, and could not be predicted from the results of single-dose studies.

Secondary structure predictions of human plasminogen and the bovine prothrombin kringle loops

Secondary structural predictions, based upon the statistical methodology of Chou and Fasman, for the kringle loops of human plasminogen and bovine prothrombin suggest a "winding staircase" pattern of beta-turns, spaced by short regions of ordered and coil structures. Analysis of the predicted structures of the regions containing the two His (113 and 387) and Asp (136 and 410) residues in plasminogen kringles 1 and 4, which have been found to be important in binding the ligand, epsilon-aminocaproic acid, shows that all are localized at the same positions on beta-turns. In addition, both of the two Asp residues occur at the end of homologous nonapeptide regions common to all of the five human plasminogen and two bovine prothrombin kringles, indicating evolutionary conservation to preserve biologically critical conformations. Examination of the protein conformation in the region of Asn288, the residue which is glycosylated in one of the two circulating variants of human plasminogen, shows that it most likely exists in a position which may present topographical hindrance to post-translational attachment of carbohydrate, thus, possibly, explaining the incomplete glycosylation of human plasminogen with complex-type carbohydrate.

Examination of the secondary structure of the kringle 4 domain of human plasminogen

The structure of a small region of human plasminogen (F4), consisting of amino acid residues Val354-Ala439 and containing its kringle 4 (K4) domain (residues Cys357-Cys434), has been predicted from Chou-Fasman calculations and hydropathy profiles, and compared to circular dichroism (CD) measurements on the isolated fragment. Calculations, by the Chou-Fasman method, of the probabilities of various types of secondary structures that exist in this region reveal that no helical structures are present. Of the total of 86 amino acid residues present in this K4-containing peptide region, 37% can adopt conformations of beta-pleated sheets, 48% of the amino acids can exist in beta-turns, and 15% of the residues can be present as coils. The structure of F4 in dilute aqueous solution has been experimentally evaluated by CD measurements. At pH = 7.4, in dilute salt solutions, a total of 64% beta-structures, 30% beta-turns, and 6% coiled structures is estimated to be present in this peptide region. Consideration of the marginal stability of many of the conformational regions of F4, as predicted by Chou-Fasman calculations, suggests that secondary structural flexibility is present in this fragment, which could result in ready adoption of new conformations. The hydropathy profile of F4 has been determined and suggests that this polypeptide is highly hydrophilic, especially in the regions of residues His387-Tyr396 and Cys406-Lys413. Thus, it appears as though a large portion of the surface of F4 can be exposed to solvent in its native conformation.

Inhibition of tolbutamide elimination by cimetidine but not ranitidine

This study was designed to compare the effects of equivalent therapeutic doses of two H2 antagonists, cimetidine and ranitidine, on tolbutamide pharmacokinetics. Twelve healthy men were given a 1-g oral dose of tolbutamide on three occasions. Subjects were randomly assigned to three treatments in a crossover fashion: cimetidine 1,200 mg/d, ranitidine 300 mg/d, and placebo. Cimetidine significantly increased the tolbutamide area under the plasma concentration-time curve by 20% (range, -5% to 42%), increased the elimination half-life by 17%, and decreased the carboxytolbutamide:tolbutamide plasma ratio from 0.042 to 0.036. Ranitidine did not significantly alter tolbutamide pharmacokinetics.