Randomized double-blind, placebo-controlled evaluation of oral ondansetron in the prevention of nausea and vomiting associated with fractionated total-body irradiation

PURPOSE

To evaluate oral ondansetron in the prevention of total-body irradiation (TBI)-induced nausea and vomiting.

METHODS

Twenty patients who received 4 days of TBI as part of their preparative regimen before bone marrow transplantation were randomized to receive either 8-mg oral doses of ondansetron or placebo. Administration of drug was double-blinded. Initial rescue therapy consisted of intravenous (i.v.) ondansetron 0.15 mg/kg following two or more emetic episodes between successive fractions of TBI or five total emetic episodes during the 4 days of therapy. If, after receipt of i.v. ondansetron, patients had two or more emetic episodes between fractions of TBI or five total emetic episodes, additional antiemetics were administered.

RESULTS

Patients who received oral ondansetron had significantly fewer emetic episodes compared with those who received placebo (P = .005) over the entire 4-day study period. Oral ondansetron was also significantly superior to placebo with respect to the time of onset of emesis or rescue (P = .003). Six of 10 patients treated with oral ondansetron completed the study without additional antiemetic therapy, while none of 10 patients who received placebo completed the study without rescue antiemetic therapy. Six placebo patients who received initial rescue therapy with i.v. ondansetron required no additional antiemetics. No relationships were apparent between peak ondansetron concentration (Cmax) or area under the concentration versus time curve (AUC) and number of emetic episodes.

CONCLUSION

Oral ondansetron is an effective therapy for the prevention of emesis induced by TBI.

Clinical safety of ondansetron

The safety of intravenous (IV) and oral ondansetron has been evaluated in over 7,000 cancer patients in world-wide clinical trials. In adult patients receiving single-day chemotherapy, the incidence of adverse events was 45% with IV ondansetron (n = 317) and 59% with metoclopramide (n = 279). Headache occurred in 17% of ondansetron patients and 10% of metoclopramide patients, whereas diarrhea symptoms were reported in 15% of the former and 29% of the latter. The incidence and types of adverse events were similar following three 0.15 mg/kg IV ondansetron doses and 8- or 32-mg single IV doses. There was a slight increase in the incidence of headache following a single 32-mg dose (25%) compared with a single 8-mg dose (18%) or three 0.15 mg/kg doses (18%). The safety profile of oral ondansetron was similar to that of the IV formulation. Following an 8-mg oral dose administered three times a day for 3 days, the most frequently reported adverse events were headache (21%), constipation (7%), and abdominal pain (5%). In a group of 209 pediatric patients receiving chemotherapy, the incidence of adverse events following IV and oral ondansetron was 19%. The most commonly reported adverse event was headache (4%). In comparative clinical trials, extrapyramidal symptoms were reported in 5% of the metoclopramide patients but none of the ondansetron patients. In open-label trials, two patients who received ondansetron reported symptoms consistent with, but not diagnostic of, extrapyramidal reactions. The incidence of vascular occlusive events and seizure disorders was identical for ondansetron and comparative agents. Serum transaminase values increased significantly in 6% to 8% of ondansetron patients and 2% of metoclopramide patients who received cisplatin. There was no apparent relationship between the dose of ondansetron administered and the incidence of increased transaminase abnormalities. However, there was an apparent relationship between the dose of cisplatin administered and the incidence of transaminase abnormalities. In patients who received non-cisplatin chemotherapy, there was no difference in serum transaminase values between oral ondansetron and placebo. These data demonstrate that ondansetron is better tolerated than metoclopramide and is safe for IV and oral administration to patients receiving chemotherapy. In addition, ondansetron is well tolerated when administered as a single 32-mg infusion over 15 minutes.

The delayed-emesis syndrome from cisplatin: phase III evaluation of ondansetron versus placebo

Cisplatin may evoke both an acute emetic response during the first 24 hours following treatment and a less well-recognized syndrome of delayed emesis. While delayed emesis is usually less severe in terms of frequency of vomiting episodes, the problem continues to result in significant morbidity. In comparison with acute emesis, the exact pathogenesis of the delayed emesis syndrome remains unclear. Although a combination of oral metoclopramide and dexamethasone is effective in many patients in preventing delayed emesis, almost 50% continue to experience at least one emetic episode when treated with this regimen. A phase III multicenter study has evaluated oral ondansetron versus placebo in the prevention of the delayed-emesis syndrome in 50 patients during days 2 through 5 following high-dose cisplatin administration. Although the daily rates of complete emetic control, failure, and control of nausea favor ondansetron, this trial is statistically inconclusive in establishing efficacy of ondansetron as a single agent in the prevention of delayed emesis. Ondansetron was well tolerated in the dose and schedule used.

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.

Ondansetron (GR 38032F): a novel antiemetic effective in patients receiving a multiple-day regimen of cisplatin chemotherapy

In a multicenter trial, we evaluated the antiemetic efficacy of ondansetron, a selective serotonin type 3 (5-HT3) receptor antagonist, in 42 adult chemotherapy-naïve patients receiving a multiple-day cisplatin regimen (20-40 mg/m2 per day for 4-5 days). Thirty-one patients received 3 daily doses of ondansetron (0.15 mg/kg) given intravenously every 6 hours (first dose 30 minutes prior to cisplatin administration); 11 additional patients received an identical dosage and schedule except that a fourth daily dose was added 17.5 hours after cisplatin administration. No other antiemetics were administered. Forty patients were evaluable for efficacy response. Thirteen patients (33%) had no vomiting at any time during the 5-day study. When emetic episodes were evaluated on a daily basis, complete protection (zero emetic episodes) ranged from 50-75%, and major protection (less than or equal to 2 emetic episodes) ranged from 65-93%. The majority of therapy failures occurred on days 3 and 4. Side effects were minor and transient; no extrapyramidal side effects were observed. Ondansetron appears to be a safe and effective antiemetic when administered during a multiple-day cisplatin-containing chemotherapy regimen.

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.

Effect of cigarette smoke on esophageal epithelium of the rabbit

Cigarette smoking is a recognized risk factor for esophageal mucosal disease. For this reason we investigated the effects of smoke on esophageal epithelial electrolyte transport and barrier function in the rabbit. Studies were performed using an extract of cigarette smoke (EOCS) prepared from high-tar, high-nicotine cigarettes. Epithelia were exposed to EOCS in vivo or in vitro in the Ussing chamber. Acute in vivo exposure to EOCS lowered in vivo esophageal potential difference by 61%, and in vitro studies established that this was due to inhibition of active Na transport from mucosa to serosa. Exposure to an EOCS had no effect on net Cl transport or epithelial permeability, the latter reflected by the absence of change in electrical resistance or mannitol flux. The ability of an EOCS to lower potential difference (and inhibit Na transport) was dose-related and equally effective whether contact occurred with the luminal or serosal surface of the tissue. Similar studies performed with an EOCS prepared from filtered smoke established that the component(s) in EOCS responsible for the effects on transport resided in the particulate phase of smoke (i.e., nicotine and "tars"). However, nicotine only inhibited Na transport from the serosal side of the tissue, thus indicating that one or more tars either cause or contribute to the effect of an EOCS on transport. The inhibition by smoke of ion transport in esophageal epithelium may well be an early deleterious link in the pathophysiological chain between cigarette smoking and esophageal mucosal disease.

Mechanisms of H+ injury in rabbit esophageal epithelium

We previously postulated that active Na transport by the esophageal stratified squamous epithelium is important for maintenance of its barrier function. To investigate this further we studied the effects of HCl on the in vivo esophageal potential difference (PD), on in vitro Na transport, and on esophageal Na-K-ATPase activity. In vivo esophageal perfusion with low concentrations of HCl (20 or 40 mM) increased the PD and a high concentration (120 mM) decreased it. An intermediate concentration (80 mM) caused a biphasic response with an initial increase in PD followed by a progressive decrease in PD. In vitro transport studies were performed to explain the increased in vivo PD. In the presence of luminal H+ the increased PD resulted from H+ diffusion from lumen to blood, whereas after H+ exposure the increased PD was due largely to increased net Na transport from lumen to blood through an amiloride-sensitive mechanism. In tissues with prolonged exposure to 80 mM HCl (PD decreased 80-100%), Na-K-ATPase activity was significantly inhibited (1.94 +/- 0.32 vs. 5.12 +/- 0.73 mumol P X mg prot-1 X h-1). Thus, HCl initially increases the in vivo esophageal PD by H+ transport from lumen to blood, a process replaced by stimulated net Na transport when H+ is replaced by Na. Prolonged acid exposure ultimately decreases Na exit from cells by inhibiting Na-K-ATPase activity. This sequence suggests that alterations in Na transport could result in cell edema and necrosis via loss of cell volume regulation.

Barrett's esophagus: clinical, endoscopic, histologic, manometric, and electrical potential difference characteristics

The clinical, endoscopic, histologic, manometric, and esophageal potential difference characteristics of 20 patients with columnar epithelia lining the lower esophagus (Barrett's esophagus) are presented. Endoscopically, two distinct types were identified: a circumferential-type and an island-type Barrett's esophagus. Patients with these types exhibited similarities in mean age, duration of symptoms, mean lower esophageal sphincter pressure, and frequency of gross esophagitis. Only patients with the circumferential lesion, however, had esophageal strictures or esophageal ulcers. Manometric testing revealed a range of lower esophageal sphincter pressures from 3 to 33 mmHg and qualitative motor abnormalities (i.e., aperistalsis, repetitive waves, tertiary waves) in 3 patients. Histologically, the frequency of epithelial types was junctional greater than specialized columnar greater than atrophic fundic epithelium. More importantly, dysplasia was identified in 2 patients with the circumferential lesion and in 1 patient with the island lesion. Potential difference measurements demonstrated that a high potential difference (greater than -25 mV) was highly specific (92%), but only moderately sensitive (70%) for detecting Barrett's esophagus. Based on these findings, we conclude (a) that there are at least two endoscopically distinct types of Barrett's esophagus involving the lower esophagus--a circumferential type and an island type, (b) that both types are associated with chronic gastroesophageal reflux, with the island type being accompanied by less severe epithelial injury than the circumferential type, and (c) that the identification of dysplasia in the two types suggests that both are unstable lesions requiring continued surveillance with endoscopy and biopsy.

Esophageal potential difference measurements in esophageal disease

To determine if esophageal transmural electrical potential difference measurements are of use for evaluating esophageal disease, we recorded potential difference in 129 patients with one or more of the following: heartburn, dysphagia, and chest pain. All potential difference studies were performed at the time of esophageal manometry using a Ringer-perfused catheter technique which yields accurate and reproducible results in healthy subjects. In 103 of the 129 patients, esophageal potential difference measurements could be correlated with findings at manometry, endoscopy, and biopsy. The remaining 26 patients had primary esophageal motor disease and were not biopsied. The results of this investigation showed: (a) that 94% of patients with gross endoscopic lesions have an abnormal esophageal potential difference, (b) that an abnormal esophageal potential difference (found in only 1 of 24 patients with normal mucosa) is highly specific for the presence of esophageal mucosal disease, (c) that the type of potential difference abnormality may suggest the nature of the mucosal abnormality, for example high potential difference with Barrett's esophagus and low potential difference with esophagitis or invasive carcinoma, and (d) that while an abnormal esophageal potential difference is highly sensitive for detecting gross esophagitis (38 of 40 patients), it is less sensitive for diagnosing microscopic esophagitis (8 of 16 patients). Based on these findings we conclude that the measurement of esophageal potential difference at the time of manometry can provide additional valuable information about the state of the esophageal mucosa.

Effect of phenolphthalein on monkey intestinal water and electrolyte transport

To assess Na-K-ATPase inhibiton and prostaglandin synthesis stimulation as the mechanism of the secretory (cathartic) action of phenolphthalein in the primate, we investigated water and electrolyte transport and Na-K-ATPase levels in monkey intestine. Both jejunum and colon were studied with in vivo perfusion and in vitro Ussing chamber techniques. Water, Na, and Cl absorption was inhibited or secretion was induced by phenolphthalein (10(-3) M) in the jejunum and colon when the drug was present in the mucosal bathing (perfusion) solution. Serosal addition of phenolphthalein (10(-4) or 10(-3) M) induced Na and anion absorption in the jejunum but not in the colon. Phenolphthalein inhibited Na-K-ATPase activity in the test tube, but assays of intestine previously perfused or bathed in the drug showed no inhibiton. Indomethacin, in doses sufficient to inhibit prostaglandin synthesis in the intestine, inhibited the secretion induced by phenolphthalein in the jejunum but not in the colon. These inconsistencies cast doubt on the role of Na-K-ATPase inhibition or the role of prostaglandin synthesis stimulation in the mechanism of action of phenolphthalein.