Shlomo Almog

Identification of an endogenous 2-monoglyceride, present in canine gut, that binds to cannabinoid receptors.

In this study, we report the isolation from canine intestines of 2-arachidonyl glycerol (2-Ara-Gl). Its structure was determined by mass spectrometry and by direct comparison with a synthetic sample. 2-Ara-Gl bound to membranes from cells transiently transfected with expression plasmids carrying DNA of either CB1 or CB2--the two cannabinoid receptors identified thus far--with Ki values of 472 +/- 55 and 1400 +/- 172 nM, respectively. In the presence of forskolin, 2-Ara-Gl inhibited adenylate cyclase in isolated mouse spleen cells, at the potency level of delta 9-tetrahydrocannabinol (delta 9-THC). Upon intravenous administration to mice, 2-Ara-Gl caused the typical tetrad of effects produced by THC: antinociception, immobility, reduction of spontaneous activity, and lowering of the rectal temperature. 2-Ara-Gl also shares the ability of delta 9-THC to inhibit electrically evoked contractions of mouse isolated vasa deferentia; however, it was less potent than delta 9-THC.

Interindividual variability in sensitivity to warfarin‐Nature or nurture?

Interindividual variability in responses to warfarin is attributed to dietary vitamin K, drug interactions, age, or genetic polymorphism in the cytochrome P4502C9 enzyme (CYP2C9) (allelic variants 2C9*2 and 2C9*3) linked with impaired metabolism of the potent enantiomere S ‐warfarin.

Combined genetic profiles of components and regulators of the vitamin K-dependent γ-carboxylation system affect individual sensitivity to warfarin

We examined the influence of combined genotypes on interindividual variability in warfarin dose-response. In 100 anticoagulated patients we quantified the effects of polymorphisms in: CYP2C9, VKORC1, calumenin (CALU), gamma-glutamyl carboxylase (GGCX) and microsomal epoxide hydrolase (EPHX1) on warfarin dose requirements. The G(1542)C VKORC1 polymorphism was associated with decreased warfarin doses in the hetero- and homozygous mutant patients (21% and 50% lower, respectively; p < 0.0001). Warfarin daily dose was predominantly determined by VKORC1 and CYP2C9 genotypes (partial r(2) = 0.21; 0.20, respectively). Together with age and body weight, these two genotypes explained 63% of the dose variance. A single patient, homozygous for G(11)A CALU mutant allele, required an exceptionally high warfarin dose (20 mg/day) and the prevalence of heterozygous (11)A allele carriers in the upper 10(th) dose percentile was significantly higher (0.27 vs. 0.18, p < 0.02). Combined genotype analysis revealed that CYP2C9 andVKORC1 wild type and CALU mutant patients required the highest warfarin doses (7.8 +/- 1.5mg/day; n = 9) as compared to the CYP2C9 and VKORC1 mutant and CALU wild type genotypes (2.8 +/- 0.3 mg/day; n = 18; p < 0.01). The odds ratio for doses <3mg/day was 5.9 (1.9-18.4) for this genotype. Compound genetic profiles comprising VKORC1, CALU and CYP2C9 improve categorization of individual warfarin dose requirements in more than 25% of patients at steady-state anticoagulation.

Improved left ventricular function after thiamine supplementation in patients with congestive heart failure receiving long-term furosemide therapy.

PURPOSE We have previously found thiamine (vitamin B1) deficiency in patients with congestive heart failure (CHF) who had received long-term furosemide therapy. In the present study, we assessed the effect of thiamine repletion on thiamine status, functional capacity, and left ventricular ejection fraction (LVEF) in patients with moderate to severe CHF who had received furosemide in doses of 80 mg/d or more for at least 3 months. PATIENTS AND METHODS Thirty patients were randomized to 1 week of double-blind inpatient therapy with either i.v. thiamine 200 mg/d or placebo (n = 15 each). All previous drugs were continued. Following discharge, all 30 patients received oral thiamine 200 mg/d as outpatients for 6 weeks. Thiamine status was determined by the erythrocyte thiamine-pyrophosphate effect (TPPE). LVEF was determined by echocardiography. RESULTS TPPE, diuresis, and LVEF were unchanged with i.v. placebo. After i.v. thiamine, TPPE decreased (11.7% +/- 6.5% to 5.4% +/- 3.2%; P < 0.01). LVEF increased (0.28 +/- 0.11 to 0.32 +/- 0.09; P < 0.05), as did diuresis (1,731 +/- 800 mL/d to 2,389 +/- 752 mL/d; P < 0.02), and sodium excretion (84 +/- 52 mEq/d to 116 +/- 83 mEq/d, P < 0.05). In the 27 patients completing the full 7-week intervention, LVEF rose by 22% (0.27 +/- 0.10 to 0.33 +/- 0.11, P < 0.01). CONCLUSIONS Thiamine repletion can improve left ventricular function and biochemical evidence of thiamine deficiency in some patients with moderate-to-severe CHF who are receiving longterm furosemide therapy.

Obesity, glucose intolerance, hyperinsulinemia, and response to antihypertensive drugs.

Responsiveness to antihypertensive medications was investigated cross-sectionally in 559 individuals comprising all treated hypertensive patients identified within a representative sample (n=3,532, aged 40-70 years) of the Jewish population in Israel. A rate of dosage score (a summed ranking of dosages of all drugs taken) of two or more increased significantly with increasing levels of body mass index (BMI) from 37.5% in levels less than 23, 54.9% in levels 23.0-29.9, and 76.4% in levels of 30 or greater (/?<0.0001). Multivariate analyses, adjusting for age, gender, arm circumference, and ethnic group, confirmed the independent effect of BMI on dosage score (p<0.001). At each level of dosage score, mean blood pressure levels were equivalent at all levels of BMI after adjusting for potential confounders. This indicates that achieved blood pressure level and not BMI itself was the main determinant of the higher dosing regimens prescribed at higher levels of BMI. In representative subgroups, glucose tolerance (n=372) and hyperinsulinemia (n=190) were determined and were found to be positively associated with a dosage score of two or more (p<0.05) independently of BMI. These effects could not be accounted for by poor compliance or by altered drug absorption or disposition since overnight urinary drug excretion and plasma drug concentrations 2 hours after ingestion, measured in 80 randomly selected patients from the study group, were not different across BMI categories at similar dosages. These findings indicate that obesity, even at mild levels, as well as glucose intolerance and hyperinsulinemia, is associated with decreased responsiveness to antihypertensive medications, perhaps as a manifestation of the insulin resistance that characterizes these conditions.

Transdermal delivery of tetrahydrocannabinol

The skin permeation behavior of a tetrahydrocannabinol (THC) is described for the first time. In the design of transdermal delivery systems, Δ8-THC was chosen over Δ9-THC due to the formers better stability and its lower psychotropic potency. Sk permeation kinetic parameters were established through rat and human skin in vitro. The rat skin was found to be about 13-fold more permeable to Δ8-THC than the human skin. Autoradiographs showed that 24 h after application the drug was concentrated in the stratum corneum, in the upper epidermis, and around the hair follicles, indicating that THC penetrates the skin through the lipophilic pathways. A transdermal formulation containing oleic acid as a permeation enhancer was tested in rats. A serum level of about 50 ng/ml cross-reacting cannabinoids (THC + metabolites) was maintained for about 24 h, indicating a sustained delivery of THC to the bloodstream. The transdermal preparation presented in this study is designed for future clinical studies.

Urinary loss of thiamine is increased by low doses of furosemide in healthy volunteers

Prolonged furosemide treatment is associated with urinary loss of thiamine and thiamine deficiency in some patients with congestive heart failure and low dietary thiamine intake. In the rat, diuretic-induced thiamine urinary loss is solely dependent on increased diuresis and is unrelated to the type of diuretic used. We studied the effects of single intravenous doses of furosemide (1, 3, and 10 mg) and of normal saline infusion (750 mL) on urinary thiamine excretion in 6 volunteers. Over a 6-hour period, furosemide induced dose-dependent increases in urine flow and sodium excretion rates (mean +/- SD), from 51 +/- 17 mL/h at baseline to 89 +/- 29 mL/h, 110 +/- 38 mL/h, and 183 +/- 58 mL/h (F = 10.4, P < .002) and from 5.1 +/- 2.3 mmol/h to 9.4 +/- 6.8 mmol/h, 12.1 +/- 2.6 mmol/h, and 20.9 +/- 10.6 mmol/h (F = 6.3, P < .005) for the three doses, respectively (104 +/- 35 mL/h and 13.0 +/- 6.2 mmol/h for the saline infusion). During this period the thiamine excretion rate doubled from baseline levels (mean of four 24-hour periods before the diuretic interventions) of 6.4 +/- 5.1 nmol/h to 11.6 +/- 8.2 nmol/h (F = 5.03, P < .01, for all four interventions, no difference being found between them), then returning over the following 18 hours to 6.1 +/- 3.9 nmol/h. The thiamine excretion rate was correlated with the urine flow rate (r = 0.54, P < .001), with no further effect of the type of intervention or sodium excretion rate. These findings complement our previous results in animals and indicate that sustained diuresis of >100 mL/h induces a nonspecific but significant increase in urinary loss of thiamine in human subjects. Thiamine supplements should be considered in patients undergoing sustained diuresis, when dietary deficiency may be present.

Urinary thiamine excretion in the rat: effects of furosemide, other diuretics, and volume load.

Long-term furosemide therapy is associated with increased urinary loss of thiamine. To examine the mechanism of furosemide-induced urinary thiamine loss, we measured urinary excretion of thiamine in rats in response to increasing doses of furosemide, acetazolamide, chlorothiazide, amiloride, mannitol, and extracellular fluid (ECF) volume loading by saline infusion. All animals were in normal thiamine balance as reflected by a thiamine pyrophosphate effect (TPPE) of 2.25% +/- 0.60% (mean +/- SEM), and all had normal renal function. Urinary flow increased in response to diuretic administration in a dose-dependent manner, reaching (mean) peak urinary flow rates of 283 to 402 microL/min. Fractional excretion of sodium (FE(Na)) exhibited the same pattern, reaching peak values of 12.3% to 23.2%. Urinary thiamine excretion increased in proportion to the incremental doses of diuretic agents, reaching (mean) maximal values of 7.44 to 9.34 pmol/min, with no significant difference (P = .11) between the various diuretics tested nor in response to saline loading. None of the diuretics tested differed in the effect on thiamine excretion, which was clearly flow dependent and only partially related to fractional sodium excretion. Urinary flow rate, being the single significant predictor, explained 78% (R2 = 0.78) of the variability in thiamine excretion rates. These findings indicate that urinary thiamine loss is caused by a nonspecific, flow-dependent mechanism common to all of the diuretics tested.

Warfarin and vitamin K intake in the era of pharmacogenetics.

The considerable variability in the warfarin dose-response relationship between individuals, is explained mainly by genetic variation in its major metabolic (CYP2C9) and target (VKORC1) enzymes. Despite the predominance of pharmacogenetics, environmental factors also affect the pharmacokinetics and pharmacodynamics of warfarin, and are often overlooked. Among these factors, dietary and supplemental vitamin K consumption is a controllable contributor to within-, and between-patient variability of warfarin sensitivity. In this commentary we review the current role of vitamin K in warfarin anticoagulation therapy, with emphasis on the following: 1 The effect of dietary and supplemental vitamin K on warfarin anticoagulation, beyond the impact of genetic variability in CYP2C9 and VKORC1. We deal separately with the effects of vitamin K on warfarin dose requirements during the induction of therapy, as opposed to its effect on stability of anticoagulation control during maintenance therapy. 2 The role of vitamin K supplementation in warfarin treated patients with vitamin K deficiency as well as in patients with unstable warfarin anticoagulation, and 3 The role of therapeutic vitamin K in cases of warfarin over-anticoagulation.

Seizures after flumazenil administration in a case of combined benzodiazepine and tricyclic antidepressant overdose

Flumazenil (Anexate®, Roche, Basel, Switzerland) is a specific, high-affinity, competitive inhibitor of the central nervous systems benzodiazepine γ-aminobutyric acid receptor, with high clinical efficacy in reversing the effects of benzodiazepine overdose (1, 2). Flumazenil is used in the emergenc