Biomedical subjects

L X Cubeddu

Publications and source records attributed to L X Cubeddu.

At least 37 records · Page 2Linked to original sources

PubMed1997

Differential effects of kainic acid on dopamine and serotonin metabolism in ventral and dorsal striatal regions.

The comparative effects of kainic acid (KA) on dopamine (DA) and serotonin (5-HT) metabolism in ventral and dorsal striatum were investigated. Local injection of KA into the caudate-putamen (CP) increased by 155% DOPAC (2,3-dihydrophenylacetic acid), by 114% HVA (homovanillic acid) and by 79% 5-HIAA (5-hydroxyindoleacetic acid) concentrations; with little or no effect on monoamine levels. The (DOPAC + HVA)/DA ratio increased from 0.33 +/- 0.2 in vehicle-treated to 0.77 +/- 0.1 in KA-treated CP. 5-HIAA/5-HT ratio increased from 2.7 +/- 0.2 to 5.9 +/- 0.1 after KA treatment. However, direct KA injections into the olfactory tubercle (OT), the most ventral part of the ventral striatum, did not alter significantly the levels of DA, 5-HT, DOPAC, HVA or 5-HIAA. Since KA is a neurotoxin which preferentially destroys perykaria and dendrites, leaving unchanged terminal boutons and axons of passage, the lack of effects on DA and 5-HT metabolism in OT suggests, that contrary to the CP, interneurons and projecting neurons in the OT play no role in inhibitory feedback mechanisms to control DA and 5-HT activities.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1997

Ventral and dorsal striatal cholinergic neurons have different sensitivities to kainic acid.

The present study was conducted to investigate the sensitivity of the cholinergic elements of ventral and dorsal striatal regions of the rat brain to the neurotoxin kainic acid (KA). Cholinergic activity was assessed by determining choline-acetyltransferase activity (CAT) and by measurements of acetylcholine (Ach) release from slices prelabeled with [3H]-choline. Direct stereotaxic injections of high-dose KA (4 micrograms/2 microliters) into specific brain regions, reduced CAT in caudate putamen (CP) by 91 +/- 1%, in nucleus accumbens (Nac) by 71 +/- 6%, but CAT in the olfactory tubercle (OT) was not affected by KA. The effects of KA on CP CAT were dose- and volume-dependent. In the OT, KA failed to affect CAT at low, moderate or high doses. Slices obtained from CP injected with KA (3 days prior) showed a 90% reduction in the electrically evoked release of [3H]-transmitter release; however, KA had no effect on transmitter release from OT. These results indicate that KA spares the cholinergic elements of the OT, and reveal the existence of marked differences in excitotoxic action of KA between ventral and dorsal striatal regions and among regions of the ventral striatum. Kainic acid preferentially damages neuronal cell bodies, dendrites and terminals intrinsic within the structures injected, with little or no effect on afferent axons and terminal boutons. Therefore, we propose that most of the Ach present in the OT may be within afferent axons and axon terminals. In the CP and NAc, KA lesions reflect loss of intrinsic cholinergic neurons. In addition, variable levels of excitatory inputs and of excitatory receptors, of the mechanisms available to reduce elevated intracellular calcium concentrations and of the levels of free-radical scavenging resources, also could account for the differences in KA neurotoxicity between OT and CP.

Acetylcholine↗

PubMed1997

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.

Acute Disease↗

PubMed1997

Relations between fasting serum insulin, glucose, and dihydroepiandrosterone-sulfate concentrations in obese patients with hypertension: short-term effects of antihypertensive drugs.

A randomized, single-blind, placebo-controlled study was conducted in 82 obese patients with mild to moderate essential hypertension, to determine the incidence of hyperinsulinemia, the relations between fasting insulin and dihydroepiandrosterone-sulfate (DHEA-S) levels, and the short-term effects of antihypertensives on DHEA-S and insulin serum concentrations. Increased insulin/glucose ratios (IGR) suggestive of insulin resistance were found in half of our patients. Hyperinsulinemic and normoinsulinemic obese patients with hypertension had comparable fasting glucose and DHEA-S concentrations and comparable blood pressure (BP) levels. Thus no relations were found between fasting insulin and DHEA-S levels. Fasting hyperinsulinemia was found in only half of the obese subjects with hypertension, suggesting that not all obese patients with hypertension are at the same high cardiovascular risk. Short-term treatment with captopril, prazosin, verapamil, atenolol, or hydrochlorothiazide (HCTZ) reduced BP; greater BP reduction was observed with drugs with vasodilatory effects. Captopril, prazosin, and verapamil reduced fasting insulin levels, whereas atenolol and hydrochlorothiazide did not. The former drugs reduced fasting insulin levels that were either within normal limits or in the hyperinsulinemic range. None of the drug treatments produced significant increases in serum DHEA-S concentrations, although some of them considerably reduced fasting insulin levels. No relations between insulin and DHEA-S levels were observed either at baseline or at the end of the antihypertensive treatment. The BP reduction resulting from the peripheral vasodilation may explain the insulin-reducing action of captopril, verapamil, and prazosin. These results further emphasize the large heterogeneity present in the pathophysiologic mechanisms operating in obesity and hypertension.

Antihypertensive Agents↗

PubMed1996

Are more antiemetic trials with a placebo necessary? Report of patient data from randomized trials of placebo antiemetics with cisplatin.

BACKGROUND: Because of the predictability of significant emesis after its use, cisplatin serves as the standard emetic stimulus for trials of antiemetic drugs. To define better the incidence, severity, and pattern of emesis that follows cisplatin, facilitate the testing of new agents, and obviate the need for further placebo-controlled trials for this indication, individual patient data were compiled from completed studies with placebo antiemetics and cisplatin. METHODS: The time and number of emetic episodes during the 24 hours after cisplatin were obtained for 48 patients given a placebo antiemetic. Each was treated as part of a randomized, double-blind trial reported between 1981 and 1990. Emesis after antiemetic "rescue" therapy was also assessed. RESULTS: Emesis occurred in 47 of 48 patients (98% observed rate, 95% confidence interval, 89-99%). The median number of emetic episodes during the 24 hours after cisplatin was 6. Emesis continued after rescue in 77% of patients. CONCLUSIONS: Cisplatin caused severe emesis that persisted despite rescue in placebo-treated patients. Using the data presented, any therapy preventing acute emesis in 8 or more of the 48 individuals receiving cisplatin > 50 mg/m2 was an active antiemetic (P = 0.05). The four trials discussed here documented the antiemetic effectiveness of granisetron, metoclopramide, and ondansetron. The placebo-treated patients studied can serve as a control group for testing new therapies. Because of the certainty of severe emesis after cisplatin, and the availability both of these data and several proven drugs for this condition, prospective comparisons of antiemetics should employ active control medications.

Adult↗

PubMed1996

Comparative dopamine-acetylcholine interactions in the ventral and dorsal striatum of rabbit and rat brain.

The dopamine (DA)-acetylcholine (ACh) interactions were investigated in dorsal (nucleus caudate, NC) and ventral (olfactory tubercle, OT) striatal regions, of rats and rabbits. Both regions receive a dense dopaminergic innervation and have high ACh concentrations. Brain slices of NC and OT from both animal species were prelabeled with [3H]choline and superfused. In rat and rabbit OT and NC, higher ACh release per pulse was elicited by lower than higher stimulation frequencies; in addition, rabbit tissues released a greater fraction of tissue [3H]transmitter than rat tissues. Blockade of D2 DA-receptors with sulpiride (1 microM), did not modify ACh release in OT and NC of rats and rabbits; suggesting that the lower ACh release observed in rat tissues is not due to an inhibitory dopaminergic tone on cholinergic neurons. Apomorphine (APO), a D2 DA-receptor agonist, inhibited in a concentration-dependent manner the evoked release of ACh from rat and rabbit NC (maximal inhibition = 90%). In rabbit OT, maximal inhibition induced by APO was 49 +/- 2% and in the rat OT, it was 23 +/- 1%. Sulpiride antagonized APO-induced inhibition of ACh release from rat and rabbit NC; however, it failed to prevent APO-induced inhibition in rat OT, and in the rabbit OT reduced it from 47% to 20 +/- 5%. These results indicate differences in the wiring of DA and cholinergic neurons and terminals in dorsal and ventral striatal structures, as well as between rat and rabbit tissues. Cholinergic ventral striatal structures may not receive a direct DA input, and afferent cholinergic nerve terminals (rather than interneurons) predominate in the ventral striatum.

Acetylcholine↗

PubMed1996

Serotonin mechanisms in chemotherapy-induced emesis in cancer patients.

Emesis is a common side effect of chemotherapeutic drugs. Cisplatin, nitrogen mustard and dacarbazine induce increases in urinary 5-hydroxyindoleacetic acid (5-HIAA) in parallel with the development of the period of emesis which is sensitive to 5-HT3 receptor antagonists ('acute emesis'). It is suggested that these cytotoxics release serotonin from enterochromaffin cells, which then acts on 5-HT3 receptors to trigger the emetic response. Cyclophosphamide, on the other hand, induces a modest emetic response, partly sensitive to 5-HT3 receptor antagonists, but not associated with increases in urinary 5-HIAA. It is suggested that cyclophosphamide-induced emesis is not mediated by the release of serotonin from enterochromaffin cells. Although after high-dose cisplatin most emesis is sensitive to 5-HT3 receptor antagonists, patients often present a milder, although more prolonged form of emesis which is mostly resistant to 5-HT3 receptor antagonists (also known as 'delayed emesis'). This form of emesis is not associated with increases in urinary 5-HIAA (not due to serotonin released from the enterochromaffin cells). Treatment with p-chlorophenylalanine (a serotonin synthesis inhibitor) inhibited cisplatin-induced emesis and cisplatin-induced increases in urinary 5-HIAA excretion. In summary, these results indicate that in human patients, serotonin plays a fundamental role in chemotherapy-induced emesis. Serotonin released from enterochromaffin cells seems to mediate emesis sensitive to 5-HT3 receptor antagonists induced by cisplatin, dacarbazine and nitrogen mustard. Emesis sensitive to 5-HT3 receptor antagonists associated with cyclophosphamide treatment, is not mediated by the release of serotonin from enterochromaffin cells by the cytotoxic. Therefore, cyclophosphamide could induce serotonin release either from enteric serotonin nerves or from the CNS. Cisplatin-induced emesis resistant to 5-HT3 receptor antagonists ('delayed emesis') is not mediated by serotonin released from enterochromaffin cells.

Antineoplastic Agents↗

PubMed1996

Differential effects of muscarinic receptor agonists and phorbol ester on muscarinic and D2-dopamine release-modulatory receptors.

The interaction between an active phorbol ester, 4-beta-phobol-12,13-dibutyrate (PDBu), and muscarinic cholinergic receptor (MAChR) agonists on the electrically evoked neurotransmitter release was studied in the striatal and prefrontal cortex (PFC) of the rabbit. MAChR agonists (carbachol and oxotremorine), physostigmine and PDBu enhanced dopamine (DA) release from striatum and prefrontal cortex. Pretreatment with PDBu antagonized the increase in DA release produced by MAChR agonists (M1 receptors). Pretreatment with MAChR agonists and physostigmine also inhibited the action of PDBu on DA release. The inhibition of ACh release from the striatum induced by MAChR agonists (M2 receptors) and by apomorphine (D2-DA receptors) was antagonized by PDBu. MAChR agonists, however, did not antagonize the effects of the D2 agonist on ACh release. In the prefrontal cortex, PDBu produced greater facilitation of DA release than in the striatum, and MAChR agonists were less effective in inhibiting the effects of PDBu on DA release. This study suggests that the facilitation of DA release induced by the MAChR agonists and that induced by PDBu occur via a similar mechanism: stimulation of protein kinase C. PDBu induces a broad-spectrum loss of responsiveness to M1-MAChR and M2-MAChR and to D2-DA release-modulatory receptors, which is probably due to massive protein kinase C stimulation, signaling cell overstimulation. MAChR agonists, on the other hand, would stimulate the protein kinase C in close proximity to the M1 ACh receptor, facilitating DA release but failing to induce broad-spectrum desensitization.

Animals↗

PubMed1995

Treatment with para-chlorophenylalanine antagonises the emetic response and the serotonin-releasing actions of cisplatin in cancer patients.

To test the role of serotonin in chemotherapy-induced nausea and emesis, ten cancer patients were pretreated with the serotonin synthesis inhibitor para-chlorophenylalanine (PCPA). PCPA (2 g 8 hourly for 2 or 3 days prior to cisplatin) reduced the spontaneous urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA), inhibited the increase in urinary 5-HIAA induced by cisplatin and markedly attenuated the acute period of nausea and vomiting associated with the cytotoxic drug. These results indicate that gastrointestinal serotonin mediates cisplatin-induced emesis and that the amount of serotonin released by cisplatin is a major factor in determining the severity of the acute period of emesis experienced by the patient.

Adult↗

PubMed1995

Comparative efficacy of a single oral dose of ondansetron and of buspirone against cisplatin-induced emesis in cancer patients.

Buspirone, an agonist of the 5-HT1A subtype of serotonin receptors, has shown antiemetic activity in animal models. However, in cancer patients treated with cisplatin, ondansetron, given either i.v. (one 8-mg dose 30 min after cisplatin) or orally (one 16-mg dose at the end of cisplatin infusion) was superior (P < 0.001) to buspirone (60 mg p.o. at the end of cisplatin and 60 mg p.o., 30 min later), in all parameters of antiemetic efficacy. These results are in favour of 5-HT3 receptors, but against the participation of 5-HT1A receptors in acute emesis associated with cisplatin chemotherapy.

Administration, Oral↗

PubMed1995

Plasma chromogranin A marks emesis and serotonin release associated with dacarbazine and nitrogen mustard but not with cyclophosphamide-based chemotherapies.

Chromogranin A (CgA) is present in high concentrations in enterochromaffin cells, where it is co-localised with serotonin in the storage granules. Plasma CgA has been reported to mark emesis and serotonin release associated with cisplatin treatment. However, it is not known whether plasma CgA could be an indicator of emesis and of serotonin release in patients receiving non-cisplatin chemotherapies. Therefore, in this study we evaluated, in cancer patients, the temporal relationships between the increases in plasma CgA and urinary 5-hydroxyindoleacetic acid (5-HIAA) and the development of vomiting following dacarbazine, nitrogen mustard and cyclophosphamide treatments. Metoclopramide was used as antiemetic. With dacarbazine, nitrogen mustard and cyclophosphamide the median time to the onset of emesis was 2.3, 2.8 and 5.3 h and the duration of intense emesis was 3, 2 and 6 h respectively. Plasma CgA and urinary 5-HIAA increased after dacarbazine- and nitrogen mustard-based chemotherapies, with maximal increases between 4 and 6 h after initiation of drug infusion. The time course for the increases in plasma CgA paralleled that of urinary 5-HIAA and the period of intense emesis. A highly significant (P = 0.0009) positive correlation (r = 0.68) was found between the increases in plasma CgA and in urinary 5-HIAA. Cyclophosphamide treatment was not associated with increases in plasma CgA and in urinary 5-HIAA, despite inducing emesis; this indicates that the increases in CgA and 5-HIAA after dacarbazine and nitrogen mustard are not due to the act of vomiting per se. In summary, plasma CgA is a marker of serotonin release (most likely from enterochromaffin cells) after dacarbazine and nitrogen mustard-based chemotherapies, exocytosis being the most likely mechanism for the release of serotonin. Serotonin released from enterochromaffin cells seems to trigger the emetic response to dacarbazine and nitrogen mustard; however, cyclophosphamide may release serotonin from a different pool (enteric serotonin neurons and/or CNS serotonin?).

Adult↗

PubMed1995

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.

Adolescent↗

PubMed1994

Effects of inhibition of serotonin synthesis on 5-hydroxyindoleacetic acid excretion, in healthy subjects.

The urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA), the main metabolite of serotonin, reflects the content and turnover of gastrointestinal (GI) serotonin. Employing longitudinal measurements of 5-HIAA, the authors investigated in healthy subjects (n = 43) how manipulations of serotonin synthesis affect GI serotonin. Under conditions of serotonin-free diets, the intersubject and intrasubject variability (coefficient of variation) for 5-HIAA excretion averaged 33% and 14%, respectively. Dietary tryptophan restrictions to 50% of minimal daily requirements (which is equivalent to a 10-fold reduction in baseline tryptophan intake) decreased by half the urinary excretion of 5-HIAA, irrespective of the caloric content of diet. Restoration to the regular tryptophan intake produced a rapid normalization of the 5-HIAA excretion. Neutral amino acids are known to compete with the intestinal transport absorption mechanisms of tryptophan. Administration of neutral amino acids (1.8 g, by mouth, three times a day, before each meal) or of carbidopa (50 mg, by mouth, three times a day for 3 days) to a normal tryptophan diet failed to alter significantly the 5-HIAA excretion. Further, neutral amino acids failed to enhance the reduction in 5-HIAA produced by the low-tryptophan diet. The failure of these treatments to reduce 5-HIAA excretion could be due to large capacity transport and decarboxylation systems for tryptophan. Other possibilities are discussed. In summary, dietary tryptophan is essential for the maintenance of GI serotonin. Reductions or increases in dietary tryptophan are the easiest and most effective method to alter GI serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Efficacy of oral ondansetron, a selective antagonist of 5-HT3 receptors, in the treatment of nausea and vomiting associated with cyclophosphamide-based chemotherapies. Ondansetron Study Group.

We evaluated the efficacy and safety of oral ondansetron, a selective antagonist of 5-HT3 receptors, for the treatment of nausea and vomiting associated with cyclophosphamide-based chemotherapy (> 500 mg/m2). In this trial 324 chemotherapy-naive cancer patients, mostly females with breast cancer, were randomized to receive either placebo or ondansetron 1 mg, 4 mg, or 8 mg three times per day for 3 days. There were no differences in the doses of cyclophosphamide, doxorubicin, and methotrexate between the study groups. All ondansetron dose groups were superior to the placebo control group (p < .001) for all measured efficacy parameters (complete response, number of emetic episodes, therapeutic failures, need of rescue antiemetics). No emetic episodes were reported by 9 (12%), 29 (37%), 48 (64%), and 47 (66%) of the placebo patients and the 1-mg, 4-mg, and 8-mg dose of ondansetron patients, respectively. Nausea was reduced and food intake was improved for all the ondansetron groups. A more severe emetic response was observed in patients receiving cyclophosphamide and doxorubicin combination chemotherapy. In this subgroup of patients, 66%, 38%, 25%, and 16% of the placebo group and 1-mg, 4-mg, and 8-mg ondansetron patients, respectively, required rescue antiemetics. No significant toxic effects were observed in this study. A higher incidence of headaches and gastrointestinal complaints (constipation, abdominal pain) were observed in the three ondansetron groups. In conclusion, oral ondansetron is an effective and well-tolerated antiemetic treatment in the management of cancer patients receiving ambulatory cyclophosphamide-based chemotherapy. These results support the view that serotonin and 5-HT3 receptors play an important role in cyclophosphamide-induced nausea and vomiting.

Administration, Oral↗

PubMed1994

Behavior of mesocortical dopamine terminals during single and repetitive stimulation: comparison with nigrostriatal neurons.

The present study reinvestigates the role of autoinhibition in dopamine (DA) release from mesoprefrontal and nigrostriatal DA neurons using improved methodology. Slices of rabbit prefrontal cortex (PFC) and striatum (STR) were labeled with [3H]DA and superfused in the presence of nomifensine (3 microM). Overflow was elicited by field stimulation with a single pulse (autoinhibition-free condition) or trains of pulses (4, 16 and 64) delivered at 0.05 to 30 Hz. One-pulse stimulation caused a measurable overflow of tritium in the PFC and STR (0.12% vs. 0.21% of tissue tritium, respectively). At increasing numbers of pulses, per-pulse over-flow decreased at all frequencies, but it was consistently more pronounced in the STR than in the PFC (e.g., 64 pulses/3 Hz: -30% PFC, -70% STR). The frequency dependence of DA release was biphasic at all numbers of pulses with overflow largest at 0.05 Hz and smallest at 3 Hz. In the PFC, however, the magnitude of the changes was considerably smaller, and the per-pulse release at higher frequencies was much larger than in the STR. The DA D2-receptor antagonist sulpiride (3 microM) enhanced pulse-train-evoked overflow from the STR at all frequencies between 0.3 and 10 Hz, whereas facilitation in the PFC was achieved at 10 Hz only. One-pulse-evoked overflow was not facilitated by sulpiride in either region. In conclusion, DA overflow from PFC terminals is not generally higher than overflow from STR terminals, as suggested in earlier studies. Larger per-pulse overflow from mesoprefrontal DA neurons occurs only under intense stimulation and is only in part a consequence of weak autoinhibition in this region.

Animals↗

PubMed1993

Participation of serotonin on early and delayed emesis induced by initial and subsequent cycles of cisplatinum-based chemotherapy: effects of antiemetics.

The role of serotonin as the possible trigger mechanism of vomiting associated with chemotherapeutic drugs was further investigated in cancer patients (n = 86). Increases in 5-hydroxyindoleacetic acid (5-HIAA) excretion rates (2.5-2.9 times baseline values) were observed 4 to 8 hours after high-dose cisplatinum (> or = 50 mg/m2). The daily excretion of 5-HIAA from 24-48, 48-72, and 72-96 hours after cisplatinum was not different from pre-cisplatinum levels. These results, together with the efficacy data for 5-HT3 antagonists, suggests that serotonin may trigger the early, intense period of emesis, but not the period of delayed emesis, following high-dose cisplatinum. Compared with the first cycle of chemotherapy, higher peak levels and more sustained elevations of 5-HIAA excretion were found after subsequent cycles, with high-dose cisplatinum. Further, no evidence of serotonin depletion was found after a single or after repeated cycles of treatment with high-dose cisplatinum. These data suggest that the more intense emetic response associated to repeated cycles of treatment may be triggered by greater changes in serotonin release. No significant differences in the rate and amount of 5-HIAA excreted induced by low-dose (30 +/- 2 mg/m2) and high-dose (84 +/- 3 mg/m2) cisplatinum were found between those patients who received dexamethasone (D) (20 mg i.v.) and those who received metoclopramide (M) (2 mg/kg, i.v.), irrespectively of the cycle of treatment. Interestingly, for M but not for D, best antiemetic protection was observed when lower amounts of serotonin were released (i.e., low-dose cisplatinum and initial cycles of treatment).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Changes in serotonin metabolism in cancer patients: its relationship to nausea and vomiting induced by chemotherapeutic drugs.

The metabolism of serotonin was studied in cancer patients of their first day of their first course of chemotherapeutic drugs either with strongly or moderately emetogenic regimens. It was observed that strongly emetogenic treatments induce greater increases in serotonin release than moderately emetogenic regimens. High-dose cisplatinum (75 +/- 5 or 83.8 +/- 5 mg m-2) produced a marked increase in the plasma levels and in the urinary excretion of 5-hydroxyindole acetic acid (5-HIAA). Neither platelet nor plasma (platelet-free plasma) serotonin were significantly modified by high-dose cisplatinum. Dacarbazine (283 +/- 22 mg m-2), another strongly emetogenic agent, induced acute nausea and emesis paralleled by marked increases in the urinary excretion of 5-HIAA. Both for high-dose cisplatinum and dacarbazine, the increases in serotonin metabolism occurred with a similar time-course than those of vomiting, and lasted for a period of 4 to 8 h. Low-dose cisplatinum (30.8 +/- 3 mg m-2) as well as cyclophosphamide-based chemotherapies (520 +/- 30 mg m-2) produced very small increases in the urinary excretion of 5-HIAA. Platelet and plasma serotonin levels failed to increase in cyclophosphamide-treated patients. Octreotide, a long-acting somatostatin analog, did not inhibit the increase in urinary 5-HIAA and the nausea and vomiting produced by high-dose cisplatinum. These results suggest that for treatments that induce marked increases in serotonin release such as high-dose cisplatinum or dacarbazine: (a) the amount and time course of serotonin release induced by chemotherapeutic drugs determines the severity, time of onset and pattern of emesis observed; (b) platelet serotonin play no role in chemotherapy-induced emesis; (c) strongly emetogenic regimens release serotonin from enterochromaffin cells; and (d) intestinal release of serotonin is the consequence of the damage induced by the chemotherapeutic drugs on the gut mucosa.

Adult↗

PubMed1992

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)

Blood Pressure↗