The role of prostaglandins in the excessive nausea and vomiting after intravascular cis-platinum therapy

The cellular mechanisms of the antiemetic action of dexamethasone and related glucocorticoids against vomiting

Glucocorticoids, used primarily as anti-allergic and anti-inflammatory drugs, are also effective, alone or combined with other antiemetics, for preventing nausea and vomiting. Dexamethasone, one of the glucocorticoids, has been suggested as a first-line drug for preventing low-level emetogenic chemotherapy- and radiotherapy-induced nausea and vomiting, and in patients with only one or two risks for postoperative nausea and vomiting (PONV). Dexamethasone combined with 5-HT3 or tachykinin NK1 antagonists is also suggested for higher-level emetogenic chemotherapy and radiotherapy and for patients at high risk for PONV. Glucocorticoids may act via the following mechanisms: (1) anti-inflammatory effect; (2) direct central action at the solitary tract nucleus, (3) interaction with the neurotransmitter serotonin, and receptor proteins tachykinin NK1 and NK2, alpha-adrenaline, etc.; (4) maintaining the normal physiological functions of organs and systems; (5) regulation of the hypothalamic-pituitary-adrenal axis; and (6) reducing pain and the concomitant use of opioids, which in turn reduces opioid-related nausea and vomiting.

Antiemetic effect of dexamethasone on cisplatin-induced early and delayed emesis in the pigeon

We investigated the ability of dexamethasone to attenuate cisplatin (4 mg/kg, i.v.)-induced early and delayed emesis. These appear within the first 8-h period (early phase) and between 8 and 48 h (delayed phase), respectively, after cisplatin administration in the pigeon. Dexamethasone (0.1 and 1 mg/kg, i.m.) reduced significantly the number of emetic responses to cisplatin by 56% and 82% (P<0.05), respectively, in the early phase, and by 41% and 66% (P<0.05), respectively, in the delayed phase. Dexamethasone (1 and 10 microg/kg, i.c.v.) reduced the number of emetic responses by 66% and 91% (P<0.05), respectively, in the early phase, and by 56% and 87% (P<0.05), respectively, in the delayed phase. Indomethacin (10 mg/kg, i.m.) did not suppress cisplatin-induced early and delayed emesis. Dexamethasone (1 mg/kg, i.m.) did not affect the content of platinum in the medulla oblongata after cisplatin administration. The above results suggest that dexamethasone has antiemetic effects on both the early and delayed emetic responses to cisplatin in pigeons, partially via its central site of action, and that the antiemetic mechanism of dexamethasone is related to factors other than its inhibition of prostanoid synthesis or its membrane stabilizing effect which reduces influx of cisplatin into the medulla oblongata.

The COX inhibitors indomethacin and meloxicam exhibit anti-emetic activity against cisplatin-induced emesis in piglets

We analysed the effects of four cyclooxygenases (COX) inhibitors on cisplatin-induced emesis in piglets. Ninety-five animals receiving cisplatin (5.5 mg kg(-1), i.v.) were observed for 60 h. One hour prior to cisplatin, controls (n=29) were dosed with a saline solution while experimental animals received an i.v. or i.p. injection of one of the COX inhibitors. Additional injections of COX inhibitor were given at 15 and 39 h after cisplatin administration (or every 6h in one group receiving diclofenac). The latencies to the first emetic episode (EE) compared to controls (2.1+/-0.4 h) increased in groups receiving naproxen (4.66+/-0.94 h, n=9, 30 mg kg(-1)) and indomethacin (6.19+/-1.13 h, n=7, 10 mg kg(-1)) i.v. Indomethacin significantly decreased the incidence of both the acute (by 40%) and delayed (by 66%) phases of emesis. The total number of EE during the 60 h compared to controls (28.3+/-1.9 EE) was significantly reduced in piglets receiving indomethacin (14.9+/-3.2 EE, n=7) and meloxicam (17.6+/-3.6 EE, n=11, 0.3 mg kg(-1)). Four piglets receiving meloxicam (0.3 mg kg(-1), i.v.) did not vomit during the delayed phase. The anti-emetic activity of two COX inhibitors suggests that prostaglandins contribute to the activation of the emetic reflex in response to cisplatin.

The interaction of dexamethasone with ondansetron on drug-induced emesis in the ferret

The potential of dexamethasone (0.5-20 mg/kg i.p.) to antagonize the emesis induced by cisplatin (10 mg/kg i.v.), apomorphine (0.25 mg/kg s.c.), morphine (0.5 mg/kg s.c.) and copper sulphate (100 mg/kg intragastric) was investigated alone and in combination with ondansetron in the ferret. There was a trend for dexamethasone 0.1-5 mg/kg to reduce cisplatin-induced emesis and for 0.05-2.5 mg/kg to delay the onset of apomorphine-induced emesis but doses of dexamethasone up to 20 mg/kg were without effect to modify morphine- or copper sulphate-induced emesis. The combination of dexamethasone 2.5 mg/kg with ondansetron 0.1 mg/kg did not have additive effects to reduce cisplatin-induced emesis but did reduce significantly the total numbers of episodes recorded. Ondansetron 1 mg/kg was without effect to modify apomorphine-, morphine- or copper sulphate-induced emesis but the combination pretreatment of ondansetron 1 mg/kg with dexamethasone 2.5 and 5 mg/kg reduced significantly apomorphine-induced retching. Data are discussed in terms of the antiemetic effectiveness of dexamethasone to antagonize chemotherapy-induced emesis in man.

Adrenal corticosteroids as antiemetics during cancer chemotherapy

Adrenal corticosteroids were first reported in 1979 to have antiemetic effects during cancer chemotherapy. Since then considerable numbers of trials have been conducted to evaluate their activity alone and in combination with other agents. The majority of the research has centered on dexamethasone, although other corticosteroids have been studied. Dexamethasone as a single agent is superior to placebo and appears to be more effective than standard doses of prochlorperazine when administered with highly emetic agents. Dexamethasone is comparable to metoclopramide against moderately emetogenic agents and low-dose cisplatin, but less effective than metoclopramide against highly emetic agents or high-dose cisplatin. Dexamethasone improves the activity of prochlorperazine and metoclopramide and may reduce some of the side effects associated with the latter. Current trials continue to explore the role of corticosteroids alone and in combination with antiemetics.

The control of cancer chemotherapy-induced nausea and vomiting

The incidence and consequences of the nausea and vomiting induced by many cancer chemotherapeutic regimes are explored and the emetogenic potential of the commonly used cytotoxic drugs evaluated. The physiology and pharmacology of chemotherapy-induced vomiting is largely unresolved but the postulated mechanisms are described and related to known properties of anti-emetic agents. The difficulties associated with the design and evaluation of trials assessing the effectiveness of single agent or combination therapy for this indication are discussed. After identifying general principles of anti-emetic prophylaxis, a critical evaluation is made of the effectiveness of the following drugs or classes of drugs, based on the available data: antihistamines, anticholinergics, phenothiazines, butyrophenones, domperidone, metoclopramide, cannabinoids, corticosteroids and benzodiazepines. Although there are still insufficient data to allow absolute recommendations to be made regarding the choice of anti-emetic therapy, considerations which should govern drug choice are listed and an algorithm presented as an aid to decision making. The contributions that can be made by a pharmacist in this area of drug use are noted.

Prostacyclin and thromboxane in gynecology and obstetrics

The gynecologic and obstetric implications of the smooth muscle-relaxing, antiaggregatory prostacyclin and its endogenous antagonist, thromboxane A2, are reviewed. In addition to the vascular wall and circulating platelets, which are primary sources for prostacyclin and thromboxane A2, respectively, reproductive tissues produce great amounts of these prostanoids, evidently for the regulation of the vascular tone and/or vascular platelet interaction. Several gynecologic and obstetric disorders are characterized by abnormalities in prostacyclin and/or thromboxane A2. In primary menorrhagia the uterine release of prostacyclin is increased, and consequently menstrual blood loss can be reduced with various prostaglandin synthesis inhibitors. Prostacyclin relaxes the nonpregnant myometrium in vitro and may also do so in vivo, although intravenous infusion of prostacyclin has no effect upon the uterine contractility in nonpregnant or pregnant subjects. Patients with pelvic endometriosis may have increased levels of prostacyclin and thromboxane A2 metabolites in the peritoneal fluid. The prostacyclin/thromboxane A2 balance shifts to thromboxane A2 dominance in patients with gynecologic cancer. During pregnancy the production of prostacyclin and thromboxane A2 increases in the mother and fetoplacental tissue. Preeclampsia and other chronic placental insufficiency syndromes are accompanied by prostacyclin deficiency in the mother and in fetomaternal tissues and by an overproduction of thromboxane A2, at least in the placenta. These changes may account for the vasoconstriction and platelet hyperactivity, which are pathognomonic for hypertensive pregnancies. By directing the prostacyclin/thromboxane A2 balance to prostacyclin dominance (by dietary manipulation, administration of prostacyclin and/or its analogues, drugs with prostacyclin-stimulating and/or thromboxane A2-inhibiting action), it may be possible to prevent and/or treat hypertensive pregnancy complications in the future.

Improved control of cisplatin-induced emesis with a metoclopramide-dexamethasone combination

Twenty-four patients receiving combination chemotherapy including cisplatin at a dosage of 50 mg/m2 were entered on this antiemetic randomized open cross-over study. High-dose dexamethasone (DXM) (regimen A) was compared with the combination of DXM and high doses of metoclopramide (MCP) (regimen B). Five patients (20%) treated with regimen A and 13 (54%) treated with regimen B suffered neither nausea nor vomiting (P less than 0.05). Regimen B was found to be significantly more effective than regimen A for all the parameters of evaluation considered. No severe side-effects were observed.

Randomized open cross-over trial between metoclopramide (MCP) and dexamethazone (DXM) for the prevention of cisplatin-induced nausea and vomiting

Thirty-five patients receiving chemotherapeutic regimens including cisplatin (CDDP) were entered into a randomized open cross-over trial. Sixteen patients had previously received chemotherapy. Metoclopramide (MCP) was given i.v. in 4 doses of 1 mg/kg over a period of 4 1/2 hr, dexamethazone (DXM) was administered i.m. in 4 doses of 8 mg over 24 hr and another 10 mg i.v. just prior to CDDP administration. Sixteen patients who expressed a positive opinion on both previous antiemetics were given placebo (PLC). No significant differences were found between MCP and DXM, considering the mean score of both emesis intensity and patient's opinion. The mean duration of the symptoms was significantly longer with MCP than with DXM (P less than 0.02). Both antiemetic agents were more effective than PLC. No significant side-effects were observed. The results of this study indicate that both MCP and DXM provide a similar protection against CDDP-induced nausea and vomiting.

Prostacyclin and thromboxane in ovarian cancer: effect of cytostatics and prostaglandin synthesis inhibitors

The production of the antiaggregatory prostacyclin (PG1(2) ) and proaggregatory thromboxane A2 (TxA2) were studied in 19 patients with residual ovarian cancer. The plasma 6-keto-PGF1 alpha (a metabolite of PG1(2) ) in cancer patients (146.7 +/- 14.7 pg/ml, mean +/- SE) was higher (P less than 0.02) than that in the controls (85.3 +/- 9.2 pg/ml, n = 17). Also the releases of TxB2 (a metabolite of TxA2) during spontaneous clotting of the blood samples were greater (P less than 0.05) in the patients (253.4 +/- 30.1 ng/ml) than controls (183.2 +/- 19.8 ng/ml). The combined administration of doxorubicin, cyclophosphamide and cis-platinum temporarily decreased the plasma 6-keto-PGF1 alpha levels but caused no changes in TxB2 generation. Prostaglandin synthesis inhibitors (acetylsalicyclic acid or indomethacin) during cytostatic infusion did not prevent the occurrence of the acute side effects of cytostatics, but they inhibited the TxB2 generation. Thus our data suggest that residual ovarian cancer is accompanied by increased production of PG1(2) and TxA2, and that prostaglandins have no role in the acute side effects of cancer chemotherapy.