Microalbuminuria: do we need a new threshold?

Microalbuminuria (30-300 mg of albumin/24 h) is a well-known independent risk factor for kidney and cardiovascular disease and of mortality in diabetic, hypertensive and in the general population. However, recent studies indicate that increased risk is observed at levels of albuminuria much lower than those currently employed to define microalbuminuria. Such low levels were shown to predict heart disease and death, independent of age, sex, renal function, diabetes, hypertension and lipids, in subjects with cardiovascular disease, hypertension and in the general population; as well as to predict progression to hypertension. Correction of obesity and metabolic derangements lowered levels of albuminuria below 30 mg/24 h to levels not associated with increased risk (5-7 mg/24 h). Despite the lack of outcome studies, there is substantial evidence to indicate that the threshold for defining microalbuminuria (that is, albuminuria associated with increased risk) should be lowered by nearly three to four-fold from the currently defined threshold. It would be advisable that clinical scores and future guidelines would consider including microalbuminuria at the lower rates as an independent risk factor, and as an indication for implementing early intervention. Unfortunately, and despite the abundance of evidence, albuminuria measurements are still underutilized in clinical practice.

Increased blood pressure reactivity to dietary salt in patients with the metabolic syndrome.

The metabolic syndrome is a predictor of type II diabetes mellitus and cardiovascular disease. The mechanisms of the increased blood pressure (BP) in patients with the metabolic syndrome are poorly understood. We investigated if salt-sensitivity is a characteristic of the metabolic syndrome. A total of 301 subjects (87 male subjects, 214 female subjects) of 41.5+/-0.7 years of age completed a salt sensitivity test, and were evaluated for the presence of metabolic syndrome. BP and 24-h sodium excretion were obtained under usual, high- and low-salt intakes. BP reactivity to salt was markedly increased in subjects with the metabolic syndrome; its magnitude was directly related to the severity of the syndrome. Reducing dietary salt from the average usual intake (8.2 g/day) to nearly 2.3 g/day lowered systolic blood pressure (SBP) by 8.7+/-1.3 mm Hg in subjects with four and five traits, 6.0+/-1.1 in those with three traits and failed to modify the BP of subjects with one or no traits of the syndrome (P < 0.0001). Salt restriction reduced the percentage of subjects with metabolic syndrome that were hypertensive (8.2 g/day of salt) from 23.8 to 8.2% (chi2: 23.6; P<0.0001). BP of non-hypertensive subjects with metabolic syndrome was also significantly reduced by salt restriction (7.1+/-1.5 and 4.2+/-1.1 mm Hg in those with four or five traits and three traits, respectively). In conclusion, the metabolic syndrome is a strong clinical predictor of salt sensitivity. The enhanced BP reactivity to dietary salt observed in subjects with the metabolic syndrome, may determine the increased BP levels commonly associated with the syndrome.

Effects of lifestyle changes and metformin on salt sensitivity and nitric oxide metabolism in obese salt-sensitive Hispanics.

Salt sensitivity is associated with obesity, and increased cardiovascular morbidity and mortality. We investigated whether treatment of obesity and its associated metabolic abnormalities corrects salt sensitivity and restores impaired nitric oxide (NO) metabolism characteristic of salt sensitivity. Twenty, otherwise, healthy obese salt-sensitive subjects completed a 12-month program of caloric restriction, aerobic exercise and metformin. Two salt sensitivity tests were performed, that is at baseline and end of program. Lifestyle-metformin treatment decreased weight (9.8+/-0.3 kg), body mass index (3.9+/-0.2 kg/m(2)), waist (11.5+/-0.5 cm), systolic blood pressure (SBP) (8.6+/-0.4 mm Hg), diastolic blood pressure (DBP) (5.5+/-0.4 mm Hg), triglyceride (40+/-5 mg/dl), fasting (8.3+/-1 microIU/ml) and post-load (20+/-4 microIU/ml) insulin levels, and salt sensitivity. Going from a high-sodium ( approximately 300 mmol) to a low-sodium diet ( approximately 30 mmol of sodium/day) lowered SBP/DBP by 14.7+/-1.7/7.4+/-0.9 mm Hg at baseline and by 8.6+/-1.9/3.2+/-1.2 mm Hg after treatment (P<0.001). More importantly, blood pressure (BP) sensitivity to customary levels of dietary salt ( approximately 150 mmol of sodium/day) was abolished by the lifestyle-metformin treatment. Differences in SBP/DBP between usual and low salt averaged 11+/-1/8+/-1 mm Hg before treatment, and 3+/-1/1+/-0.5 mm Hg after treatment (P<0.001). At baseline, NO-metabolite excretion was inhibited during high salt; this impairment was corrected by the lifestyle-metformin treatment. In conclusion, acquired correctable factors play an important role in the pathogenesis of salt sensitivity associated with obesity. Correction of salt sensitivity may account for the BP lowering induced by weight reduction. Restoration of the inability to increase or sustain NO production in response to high salt could account for the correction of salt sensitivity induced by the lifestyle-metformin treatment.

NAD(P)H oxidase p22phox gene C242T polymorphism, nitric oxide production, salt sensitivity and cardiovascular risk factors in Hispanics.

Mutations in the NAD(P)H oxidase gene may be associated with abnormal superoxide generation, nitric oxide (NO) availability and cardiovascular diseases. We investigated the prevalence of the NAD(P)H oxidase p22phox gene C242T polymorphism, and its possible association with blood pressure, NO production, salt sensitivity and cardiovascular risk factors in Hispanics. Genotype frequencies were as follows: CC, 52.9%; CT, 40.3%; and TT, 6.8%. There were no significant differences in systolic blood pressure, diastolic blood pressure, age, weight, fasting and post-load glucose levels, LDL and HDL cholesterol, triglyceride and urinary albumin levels in subjects with CC, CT or the TT genotypes. Presence of the T allele was associated with increased salt sensitivity in women, but not in men. NO metabolite excretion was markedly decreased both in women and men with the TT genotype (CC: 868+/-79 micromol/day; CT: 839+/-75 micromol/day; TT: 534+/-78 micromol/day; P<0.05). In conclusion, the prevalence of the NAD(P)H oxidase p22phox gene C242T polymorphism in Venezuelans was comparable to that of Caucasians, but different from that of Chinese and Japanese. Although the T allele was not associated with cardiovascular risk factors, hyperinsulinaemia or hypertension, in women, it appeared to be a genetic susceptibility factor for salt sensitivity. Both in women and men, the p22phox gene may play a role in the genetic control of NO levels.

Plasma chromogranin A: a marker of serotonin release and of emesis associated with cisplatin chemotherapy.

PURPOSE: Emesis is a common side effect of cancer chemotherapy. Serotonin released from gastrointestinal enterochromaffin cells (ECC) may mediate chemotherapy-induced emesis. Since chromogranin A (CgA) is colocalized in ECC storage granules with serotonin, we tested the hypothesis that plasma CgA could mark emesis and serotonin release from ECC. PATIENTS AND METHODS: The relationships between plasma CgA, serotonin release, and the development of vomiting following the first course of cisplatin chemotherapy were evaluated in 60 patients. RESULTS: CgA levels increased in 59 of 60 patients (245% +/- 18% increase above baseline levels, P < .001). The time course of the increase in plasma CgA matched that of emesis and of urinary 5-hydroxyindoleacetic acid (5-HIAA). Significant (P < .001) positive correlations were found between the dose of cisplatin and the increases in plasma CgA, and between the changes in plasma CgA and urinary 5-HIAA after cisplatin (r = .54, n = 39, P < .001). The increase in plasma CgA after cisplatin did not correlate with changes in serum lactic dehydrogenase (LDH) activity, a marker of cell toxicity or lysis. CONCLUSION: Plasma CgA marks emesis and serotonin release induced by cisplatin. Since both CgA and serotonin are costored in ECC granules, we suggest that the source of release of each may be the ECC. Increases in plasma CgA are not explained by drug cytotoxicity. Exocytosis appears as the main mechanism by which cisplatin releases serotonin. This work further supports the role of serotonin as a mediator of emesis associated with cisplatin and suggests that plasma CgA level is a valuable tool in studies of chemotherapy-induced emesis.

Antagonism of serotonin S3 receptors with ondansetron prevents nausea and emesis induced by cyclophosphamide-containing chemotherapy regimens.

The control of nausea and emesis in cancer patients receiving chemotherapy poses a significant management problem. In this randomized, double-blind, placebo-controlled study, we evaluated the effect of serotonin S3 receptor blockade with ondansetron (GR 38032F) on the prevention of nausea and vomiting induced by cyclophosphamide-containing chemotherapy. Cyclophosphamide was given in doses of 500 to 600 mg/m2 and ondansetron as three intravenous (IV) doses of 0.15 mg/kg. Most patients had breast cancer. Cyclophosphamide was given in combination with doxorubicin (65% of patients) or with fluorouracil (85% of patients: 50% with Adriamycin [doxorubicin; Adria Laboratories, Columbus, OH] and 35% with methotrexate). All placebo-treated patients experienced vomiting, whereas 70% of patients treated with ondansetron did not vomit (P = .008). Median nausea scores were 8 mm on ondansetron and 65 mm on placebo (P less than .001). Seventy percent of patients treated with ondansetron retained their normal appetite, compared with 10% of placebo patients. Adverse events occurred in six placebo patients and one ondansetron patient. Diarrhea and headache were the most common events, both occurring more frequently in the placebo group. There were no extrapyramidal reactions, and the only significant biochemical change occurred in a placebo-treated patient. These results suggest that serotonin S3 receptor antagonists represent a novel, effective, and safe mode of therapy for nausea and emesis induced by cyclophosphamide-containing chemotherapies. In addition, our observations are compatible with the view that serotonin, acting on S3 receptors, mediates the nausea and emesis occurring after cyclophosphamide chemotherapy.

Endothelial nitric oxide synthase polymorphism, nitric oxide production, salt sensitivity and cardiovascular risk factors in Hispanics.

Mutations in the endothelial nitric oxide synthase (eNOS) gene may be associated with abnormal nitric oxide (NO) production and cardiovascular diseases. In this study, we investigated the prevalence of two eNOS polymorphisms, the Glu298Asp variant on exon 7, and the 4a/b variable number of tandem repeats (VNTR) on intron 4, and their association with blood pressure (BP), NO production, salt sensitivity and cardiovascular risk factors in healthy Venezuelans. The prevalence of both polymorphisms in Venezuelans was comparable to that described for Caucasians, but significantly different from that known for African-Americans and Japanese. The 4a/b genotype was associated with reduced levels of NO metabolites (25% decrease), larger BP lowering in response to salt restriction (9.0 vs 4.8 mmHg, P<0.05), greater prevalence of salt sensitivity (39% in 4a/b and 27% in 4b/b; P<0.05) and with higher LDL-cholesterol levels. The Glu298T polymorphism did not affect NO production, nor it was associated with salt sensitivity. Glu298Asp polymorphism was positively associated with higher weight, triglycerides and LDL-cholesterol. Neither polymorphism was associated with changes in fasting or postload serum glucose, BP, obesity and albuminuria. In conclusion, the prevalence of eNOS polymorphisms is strongly determined by ethnic factors. The 4a/b gene polymorphism could be a genetic susceptibility factor for the BP response to salt intake and for the genetic control of NO production. The reduced NO production in subjects with the 4a/b genotype may be responsible for the increased sensitivity of their BP to salt.

Cerebrospinal fluid and plasma dopamine-beta-hydroxylase activity in human hypertension.

Cerebrospinal fluid (CSF) and plasma dopamine-beta-hydroxylase (DBH) activity was measured in 22 normotensive (NT), 31 essential hypertensive (EH), and 11 renal hypertensive (RH) patients. Although no differences were observed in their plasma DBH, the mean CSF-DBH activity and specific activity of EH were significantly lower than those of NT and RH patients. Very low CSF-DBH (less than 0.15 units/ml of CFS or less than 0.5 units/mg of CSF protein) was found only in EH (26% of EH). Of the 31 EH patients, 19(60%) had CSF-DHB activities lower than 0.5 units/ml, whereas only 5 of 22 NT (23%) and no RH fell within this range. Nevertheless, 20% of EH, 55% of NT, and 40% of RH patients had CSF-DBH activities above the mean value for NT (less than 0.9 units/ml). NT subjects with very low plasma DBH (less than 50 units/ml) had CSF-DBH activities that fell within normal range. With the exception of these subjects, the specific activity of CSF-DBH was always lower than that of the plasma enzyme. The concentration of albumin, alpha 1, beta, and gamma globulins was measured in plasma and CSF obtained from the last five NT, four EH, and two RH patients. A positive linear relationship was obtained when the log of the plasma/CSF concentration ratio for these proteins was plotted against their molecular weight. Similar slopes and intercepts were obtained for these patients, suggesting that no major differences seem to exist in their blood-brain-barrier permeability to proteins. The results suggest that measurements of CSF-DBH could be of help in the differential diagnosis of human hypertension and in the neurochemical characterization of EH. If CSF-DBH reflects central noradrenergic activity, its reduction might indicate the existence of a central catecholaminergic defect in a subgroup of EH patients.

Levels and molecular properties of secretoneurin-immunoreactivity in the serum and urine of control and neuroendocrine tumor patients.

We have determined the levels of secretoneurin (SN), a novel 33-amino acid neuropeptide belonging to the class of chromogranins, in the serum and urine of healthy subjects and patients suffering from various tumors. SN serum levels averaged 22.1+/-1.1 fmol/mL. They were 5-fold higher in younger children and then declined continuously. SN levels were positively correlated with serum creatinine, suggesting an influence of renal function on the clearance of SN from the serum. In the urine 80.0 fmol/mL SN was present. In patients with endocrine tumors like gut carcinoids, endocrine pancreatic tumors, oat cell lung carcinomas, and pheochromocytomas, SN serum levels were elevated up to 45-fold. Patients suffering from neuroblastomas, insulinomas, pituitary adenomas including acromegaly, and solid nonendocrine tumors had concentrations in the normal range. In human serum, SN-immunoreactivity was confined to the free peptide SN; neither larger intermediate-sized forms nor the precursor secretogranin II were detected. An efficient removal of the small molecule SN from the serum by the kidney explains why SN serum levels are lower when compared to chromogranin A, which is present as large molecule in serum.

Naloxone does not antagonize the antihypertensive effect of clonidine in essential hypertension.

Reports on spontaneously hypertensive rats suggested that naloxone blocked the antihypertensive effects of clonidine. We compared the effects of an 8-hr intravenous naloxone infusion (6 micrograms/kg/hr) or 5% dextrose in water (D5/W) begun 2 hr before single oral doses of clonidine (0.3 mg) in six men with mild to moderate essential hypertension (EHT). Supine and standing (after 5 min) blood pressure (BP) and heart rate (HR) were measured every 20 min. Initial treatment with naloxone or placebo (D5/W) infusion was randomly allocated, with the alternate treatment given 1 wk later. Naloxone did not modify either supine or standing BP or HR. Clonidine induced a gradual, sustained reduction in both supine and standing systolic and diastolic BP and in supine HR, and there was an increase in standing HR. Naloxone did not modify the onset, maximal effect, or recovery of the hypotensive and HR effects of clonidine in both the supine and standing positions. Our data indicate that hypotensive and bradycardiac effects of clonidine in EHT are not mediated by naloxone-sensitive opioid receptors. They also suggest that opioid receptors play no role in the maintenance of hypertension nor in the BP and HR adjustments induced by postural changes in EHT.

Beta blockade by oral propranolol and labetalol.

beta-Adrenergic blockade after single, oral doses of labetalol or propranolol was evaluated in a double-blind, placebo-controlled study by an isoproterenol sensitivity test and handgrip exercise in 10 healthy men. The tests were performed with subjects resting in a supine position. At the doses used, there was no effect on heart rate and blood pressure in either the resting position or in the isometric exercise phase. It is possible that exercise-induced changes in blood pressure and heart rate were reduced by higher vagal tone in this young group tested in the supine position. Isoproterenol increased heart rate and reduced diastolic blood pressure in a dose-dependent manner. The dose of isoproterenol at which heart rate increased 25 bpm above the resting rate (CD25; 1.36 +/- 0.18 microgram) was of the order of that at which diastolic blood pressure fell 25 mm Hg from baseline (HD25; 1.07 +/- 0.07 microgram). There was a significant positive correlation between CD25 and HD25 in the 10 subjects. Propranolol and labetalol induced a dose-dependent, parallel shift to the right in the dose-response curves of isoproterenol effects on heart rate and diastolic blood pressure, indicating that both drugs are nonselective, competitive antagonists of beta-adrenergic receptors. On the average, propranolol was 17 and 19 times more potent than labetalol in antagonizing the chronotropic and hypotensive actions of isoproterenol, respectively.

Clinical pharmacology of doxazosin in patients with essential hypertension.

Doxazosin is a new quinazoline derivative that, like prazosin, has selectivity for alpha 1-receptors. A three-way crossover, randomized, open study in 18 patients with essential hypertension was conducted to investigate the clinical pharmacokinetics of 2, 4, and 8 mg doxazosin at steady state. The pharmacokinetics of the initial 2 mg dose was also studied. Doxazosin showed linear pharmacokinetics. Increases in doses from 2 to 8 mg (steady state) produced proportional increases in doxazosin serum levels (maximum plasma drug concentration [Cmax] minimum plasma drug concentration [C min], and O-24-hour area under the curve [AUC(p-24)], whereas half-life (t1/2) (19.4, 18.7, and 19.7 hours, respectively), volume of distribution (3.4, 3.4, and 3.6 L/kg, respectively), clearance from serum (2.2, 2.2, and 2.1 ml/min/kg, respectively), and degree of protein binding (1.2%, 1.0%, and 1.0% unbound, respectively) were dose independent. Similar t1/2 and time to reach peak concentration (tmax) were obtained with 2 mg initial dose and 2 mg steady state. alpha 1-Acid glycoprotein levels were unchanged during doxazosin treatment. Doxazosin lowered supine and standing systolic and diastolic blood pressure. The blood pressure reduction was associated with an increase in heart rate. Peak hypotensive and tachycardic effects occurred 5.7 +/- 0.1 hours after administration, whereas Cmax was achieved at 2.4 +/- 0.7 hours (tmax). Greater decreases in systolic blood pressure and increases in heart rate were seen in standing than in supine position. The reduction in standing systolic and diastolic blood pressure with 8 mg was greater than with 2 mg (P less than 0.05); however, the increases in heart rate were not different. Dizziness, headaches, and dry mouth were the most frequent side effects. This study indicates that doxazosin shows linear pharmacokinetics between 2 and 8 mg and that because of its long t1/2, once-a-day administration should be adequate for the treatment of hypertension.

Prazosin and propranolol in preoperative management of pheochromocytoma.

Combined use of prazosin and propranolol was effective in preoperative management of three patients with norepinephrine(NE)-secreting pheochromocytoma (PHEO). On admission, all were symptomatic and had moderate to severe hypertension despite treatment with diuretics, propranolol, and sympatholytics. Optimal symptomatic and blood pressure (BP) control was achieved with 6 to 10 mg/day prazosin and 120 to 480 mg/day propranolol every 6 hr in equally divided doses. With this therapy, BP and hematocrit were reduced to levels similar to those found in the postoperative period. The daily urinary excretion of catecholamines and their metabolites was not modified during therapy with prazosin and propranolol. There was a drop in supine systolic (40 to 64 mm Hg) and diastolic (32 to 52 mm Hg) BP in all patients 1 to 2 hr after the first dose of prazosin (1-mg tablet); in two subjects this was accompanied by a larger orthostatic fall (74 and 92 mm Hg systolic; 65 and 78 mm Hg diastolic BP). The high incidence of first-dose effect suggests that a single oral dose of 1 mg of prazosin could aid in the diagnosis of PHEO. The effectiveness of prazosin in controlling the hypertension induced by NE-secreting PHEO suggests that, in man, pressure responses to augmented levels of NE are mediated solely through alpha 1-receptors.

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.

Verapamil and propranolol in essential hypertension.

Twenty-four subjects with mild to moderate essential hypertension completed this 9-wk parallel, randomized, double-blind study of the antihypertensive effects of verapamil (V) (240 to 480 mg%) and propranolol (P) (120 to 360 mg%). V lowered systolic and diastolic blood pressures in all postural positions, with an average reduction of 20/16 mm Hg. With the exception of standing systolic blood pressure, P also lowered systolic and diastolic blood pressures in all postural positions, with an average reduction of 9/11 mm Hg. Differences between V and P were significant only for sitting systolic blood pressure. Heart rate was decreased by P but was not affected by V. The PR interval was prolonged by V. Plasma levels of V and P were directly related to dose. Plasma levels of V were linearly related to those of its major metabolite, norverapamil (r = 0.81). There was no correlation between clinical response and the dose or plasma level of V or P, but all subjects who received 480 mg% V had an average blood pressure reduction of 20/16 mm Hg and plasma levels of the parent drug above 200 ng/ml. V is an effective antihypertensive for mild to moderate essential hypertension. Constipation, pedal edema, and a maculopapular rash were reported as side effects of V.

Bupropion does not antagonize cardiovascular actions of clonidine in normal subjects and spontaneously hypertensive rats.

Tricyclic antidepressants (TADs) are known to antagonize the hypotensive and sedative actions of clonidine. We compared the effects of bupropion and imipramine pretreatment on the acute hypotensive and sedative actions of clonidine in eight normotensive male subjects in a randomized, double-blind crossover study. Pretreatment with bupropion, 100 mg by mouth three times a day for 9 days, had no effect on baseline supine blood pressure (BP) and heart rate (HR) and did not modify the hypotensive, bradycardic, and sedative actions of clonidine. Imipramine, 25 mg by mouth three times a day for 9 days, increased supine and standing HR and decreased standing systolic BP. In half the subjects the hypotensive action of clonidine was reduced 40% to 50% by imipramine. The specific binding of 3H-yohimbine to alpha 2-receptors of platelet membranes was not affected by pretreatment with either antidepressant. In spontaneously hypertensive rats, 16 days of bupropion, 25 mg/kg subcutaneously, had no effect on baseline BP and HR and did not antagonize the hypotensive and bradycardic effects of clonidine, 5 mg/kg iv. Pretreatment with desipramine, 5 mg/kg subcutaneously for 16 days, accelerated baseline HR and reduced cardiovascular actions of clonidine. These observations suggest that not all antidepressants antagonize the effects of clonidine. If the negative interaction between TADs and clonidine is a result of sensitivity of alpha 2-receptors, these receptor changes are not the common denominator of antidepressant activity and may only be seen with TADs.

Mechanisms by which cancer chemotherapeutic drugs induce emesis.

Because the area postrema seems essential for chemotherapy-induced vomiting, both circulating and/or neurally mediated stimuli in this area could trigger the emetic response. In our laboratories results of cross-circulation and direct intracerebroventricular infusion experiments in dogs do not support a role for circulating substances. The large increases in serum vasopressin induced by cisplatin were not blocked by inhibitors of the angiotensin-converting enzyme. In the ferret inhibition of serotonin synthesis with p-chloro-phenylalanine, administration of selective antagonists of 5-hydroxy-tryptamine3 (5-HT3) receptors, or visceral deafferentation inhibited the emetic response evoked by cisplatin or high-dose cyclophosphamide. The results suggest that serotonin plays an important role and that peripheral neural mechanisms are involved in the emetic response. The strong antiemetic efficacy of selective 5-HT3 antagonists also has been confirmed in humans. In cancer patients high-dose cisplatin increased the plasma and urinary levels of 5-hydroxy-indoleacetic acid (5-HIAA), but did not affect platelet and free plasma serotonin. The changes in 5-HIAA levels paralleled the onset and development of vomiting. No evidence of serotonin depletion has been obtained after high-dose cisplatin. Dacarbazine, another strongly emetogenic agent, increased urinary 5-HIAA; however, only small increases in 5-HIAA were produced with low-dose cisplatin or cyclophosphamide-containing regimens. Thus, emetogenicity appears to be directly related to the ability of the cytotoxic agent to release serotonin. In humans, antiemetics such as ondansetron, metoclopramide, and dexamethasone did not effect high-dose cisplatin-induced increases in serotonin metabolism. Therefore, these antiemetics seem not to affect the amount of serotonin released. The mechanism by which chemotherapeutic drugs induce serotonin release is unknown; however, release may occur by direct cytotoxicity on the gastrointestinal mucosa, including the enterochromaffin cells. Delayed emesis appears to be mediated by 5-HT3-independent mechanisms. It is proposed that emesis that develops despite high-dose ondansetron (residual emesis) should be considered delayed emesis. Residual and delayed episodes of emesis have similar time courses, are characterized by very mild emetic episodes and poor response to 5-HT3 antagonists, and are not associated with increases in serotonin metabolism.

Comparative efficacy, safety and pharmacokinetics of verapamil SR vs verapamil IR in hypertensive patients.

The antihypertensive effects of the regular immediate release formulation of verapamil (verapamil IR) and the newer sustained release formulation of verapamil (verapamil SR) were compared in Hispanic patients with untreated essential hypertension. Verapamil IR was given in 3 divided doses (80 or 160mg 3 times daily) and verapamil SR was given either as a single daily dose of 240mg or as 240mg every 12 hours. With both formulations there was a significant reduction in systolic (SBP) and diastolic blood pressure (DBP); a greater lowering of BP was observed with verapamil 480 mg/day than with 240 mg/day. With verapamil SR 480 mg/day, 91% of patients had reductions in SBP and DBP greater than 20 and 15mm Hg, respectively. In addition, 83% of patients reached normotension. With the lower dose (240mg once daily), 83% of patients had decreases in DBP greater than 10mm Hg and 73% of patients achieved normotension. Comparable effects were achieved with verapamil IR. With verapamil IR there was a more rapid fall in BP which peaked 3 to 4 hours postdose, whereas with verapamil SR a more gradual and sustained BP reduction was observed. Only small changes in heart rate (HR) were observed with verapamil IR and verapamil SR. For verapamil SR, the mean increase in HR was 5 beats/min (to 80 beats/min) and the mean decrease in HR was 13 beats/min (to 62 beats/min). Both verapamil SR and verapamil IR prolonged the PR interval of the ECG. An equal degree of PR prolongation was observed with 240 and 480 mg/day. The incidence of side effects (headache, palpitations, dizziness and flushing) was dose dependent, decreased with continuous treatment and was much higher with verapamil IR than with verapamil SR. Steady-state plasma verapamil concentrations were monitored. Compared with verapamil IR, verapamil SR produced a more gradual rise and a more sustained elevation of plasma verapamil and norverapamil concentrations. Comparable trough verapamil concentrations (Cmin) were observed with verapamil IR (98 micrograms/L) and SR (81 micrograms/L); morning Cmin verapamil concentrations were higher than daytime Cmin values. The normalised area under the plasma concentration-time curve (AUC) and maximum concentration (Cmax) were 10 to 20% greater for verapamil IR than SR. The 2-fold increase in oral dose produced a 2.2- and 2.4-fold increase in AUC for verapamil IR and SR, respectively, associated with a 20% reduction in metabolism to norverapamil. Fasting increased the rate and extent of absorption of verapamil.(ABSTRACT TRUNCATED AT 400 WORDS)

Antiemetic activity of ondansetron in acute gastroenteritis.

BACKGROUND: The mechanism of nausea and vomiting associated with gastroenteritis is unknown. The role of 5-HT3 receptors in emesis associated with gastroenteritis was investigated in paediatric patients. METHODS: A randomized, double-blind, placebo-controlled, parallel-group study was conducted in three groups of 12 patients each, receiving either a single i.v. dose of ondansetron (0.3 mg/kg), metoclopramide (0.3 mg/kg) or placebo (sterile saline). Food was restricted and oral rehydration was administered for 4 h. RESULTS: During 0-24 h, the number of emetic episodes experienced was significantly greater (P = 0.048) with placebo (mean = 5) than ondansetron (mean = 2) and the proportion of patients experiencing no emesis was significantly greater (P = 0.039) with ondansetron (58%) than placebo (17%). A numerical difference, in favour of ondansetron, was observed between ondansetron and metoclopramide groups for both of the above parameters. Fewer treatment failures were observed with ondansetron (17%) than placebo (33%) and metoclopramide (42 %). More diarrheal episodes were observed in the groups receiving anti-emetic treatment. All three treatments were well tolerated. CONCLUSIONS: Ondansetron, a 5HT3 receptor antagonist, was significantly superior to placebo in preventing emesis associated with acute gastroenteritis, in paediatric patients. Therefore, serotonin, acting through 5HT3 receptors, may play a role in this form of emesis.

Salt sensitivity is associated with insulin resistance in essential hypertension.

The relationship between salt sensitivity and insulin resistance was investigated in nondiabetic, nonobese (body mass index < or = 28) untreated patients with uncomplicated, mild-to-moderate essential hypertension. Alterations in insulin-mediated glucose disposal were assessed by means of the insulin suppression test. Subjects were classified as salt sensitive and salt resistant according to their blood pressure response to low and high salt intake. Fasting serum glucose levels were within normal limits and did not differ between salt sensitive and salt resistant hypertensives, irrespectively of the level of salt intake. Fasting serum insulin levels increased in salt sensitive patients when on a high intake of salt. The insulin suppression test revealed the existence of marked differences in insulin-mediated glucose uptake between salt sensitive and salt resistant hypertensives. Much higher steady-state glucose values (nanomoles of glucose/ liter) were obtained during the insulin suppression test in salt sensitive than in salt-resistant hypertensives (7.4+/-1.6 v 3.5+/-0.1 under low salt; and 12.5+/-1.1 v 4.3+/-0.1 under high salt intake). The product of glucose times insulin obtained at steady state during low and high salt intakes were 2.5 and 5 times greater, respectively, in salt sensitive than in salt resistant hypertensives. Therefore, the impairment in insulin-mediated glucose disposal observed in salt sensitive hypertensives was present both under low salt (60 to 70 mEq/day) and high salt intake (300 mEq/day). However, it was exacerbated under high salt intake. These results suggest that untreated salt sensitive hypertensives have a considerable impairment in insulin-mediated glucose disposal because of a state of insulin resistance. High salt intake increased BP, induced hyperinsulinemia, and worsened insulin-mediated glucose disposal only in salt sensitive patients. We propose that salt sensitivity contributes, separately from hypertension, to insulin resistance and thus be considered per se as an additional risk factor in the development of cardiovascular disease. Salt sensitivity and insulin resistance may be genetically associated conditions.