Drugs

5-HT3 receptor antagonists for the prevention of chemotherapy-induced nausea and vomiting. A comparison of their pharmacology and clinical efficacy.

Year 1998
Gregory RE. Ettinger DS.
Johns Hopkins Oncology Center, Baltimore, Maryland, USA.
In the mid-1980s it was discovered that serotonin (5-hydroxytryptamine; 5-HT) was at least partially responsible for producing chemotherapy-induced nausea and vomiting. It was therefore realised that serotonin receptor blockade with serotonin 5-HT3 receptor antagonists could inhibit chemotherapy-induced nausea and vomiting. 5-HT3 antagonists have different chemical structures and receptor binding affinity. Granisetron, dolasetron and its major metabolite are pure 5-HT3 antagonists, while ondansetron and tropisetron are weak antagonists at the 5-HT4 receptor. Ondansetron has also been demonstrated to bind at other serotonin receptors and to the opioid mu receptor. The half-lives of granisetron, tropisetron and the active metabolite of dolasetron are 2 to 3 times longer than that of ondansetron. These observations initially suggested that more frequent ondansetron administration would be required; however, it has now been shown that receptor blockade does not correlate with elimination half-life and all 5-HT3 antagonists can be effectively administered once daily. Clinical trials have been conducted that directly compare the 5-HT3 antagonists. To compare these studies, it is necessary to assess trial design, including known risk factors for the development of chemotherapy-induced nausea and vomiting, and response criteria. Stratification for risk factors, use of strict efficacy criteria and randomisation to a blinded trial using an appropriate comparative regimen are essential for a well designed antiemetic trial. Comparative clinical trials using various doses, routes and regimens of administration have been conducted with 5-HT3 antagonists. Despite some trial design shortcomings, most of the studies show equal efficacy between the agents, especially in moderately emetogenic chemotherapy and mild, infrequently occurring adverse effects. The addition of steroids also appears to improve outcome. However, since many doses and regimens of ondansetron were used, further study is needed to determine the optimal regimen. The efficacy of 5-HT3 antagonists in controlling delayed nausea and vomiting from chemotherapy is less well studied. Further, there is no good scientific rationale for the use of 5-HT3 antagonists in controlling delayed nausea and vomiting since serotonin has not been shown to be released during the delayed phase. In fact, most studies show no benefit or modest benefit of 5-HT3 antagonists over placebo. Because the 5-HT3 antagonists perform similarly in the clinical setting, pharmacological differences do not seem to translate into therapeutic differences. There is also no appreciable difference in the incidence or severity of adverse effects among the 5-HT3 antagonists. Determination of clinical use may then be driven by cost.

Rabeprazole.

Year 1998
Prakash A. Faulds D.
Adis International Limited, Auckland, New Zealand. demail@adis.co.nz
Rabeprazole is a proton pump inhibitor with antisecretory properties. In vitro animal experiments have indicated that the inhibition of the proton pump by rabeprazole is partially reversible. Rabeprazole has 2- to 10-fold greater antisecretory activity than omeprazole in vitro. However, it dissociates more readily from H+,K(+)-ATPase than omeprazole, resulting in a shorter duration of action. In comparative clinical trials rabeprazole was significantly more effective than placebo, famotidine or ranitidine and as effective as omeprazole in the treatment of patients with erosive or ulcerative gastro-oesophageal reflux disease or gastric or duodenal ulcers. Healing rates with rabeprazole were independent of Helicobacter pylori status. Rabeprazole in combination with either clarithromycin and metronidazole or clarithromycin and amoxicillin or amoxicillin and metronidazole or clarithromycin for 7 days produced eradication of H. pylori in 100, 95, 90 and 63% of patients. The tolerability profile of rabeprazole 20mg once daily was similar to that of famotidine 20mg twice daily, ranitidine 150mg 4 times daily or omeprazole 20mg once daily in comparative trials. The adverse events reported with once daily administration of rabeprazole 20mg include malaise, nausea, diarrhoea, headache, dizziness and skin eruptions in 0.7 to 2.2% of patients.

Practical considerations in the treatment of hepatocellular carcinoma.

Year 1998
Colleoni M. Audisio RA. De Braud F. Fazio N. Martinelli G. Goldhirsch A.
Division of Medical Oncology, European Institute of Oncology, Milan, Italy. mcol@ieo.cilea.it
Hepatocellular carcinoma (HCC) represents one of the most common neoplasms worldwide. To date, curative treatment options include liver transplantation or resection. Unfortunately, most patients are detected with nonresectable or -transplantable HCC due to disease extension or comorbid factors, and are therefore candidates only for palliative treatments. Palliative medical treatments, including systemic chemotherapy, immunotherapy or hormonal manipulation, have a borderline activity on HCC and cannot be recommended outside clinical trials. A high response rate has been reported with local therapies such as transcatheter arterial embolisation, intra-arterial chemotherapy or percutaneous alcohol (ethanol) injection, but as there is no clear evidence of a survival advantage for these treatment modalities, further investigations are required. Multidisciplinary treatment, including preoperative cytoreduction or postoperative adjuvant therapy, is currently under investigation, with encouraging survival results. HCC patients should be evaluated within clinical trials, possibly randomised and with homogeneous prognostic factors, in order that we may find the answer to all these important questions.

Raltitrexed. A review of its pharmacological properties and clinical efficacy in the management of advanced colorectal cancer.

Year 1998
Gunasekara NS. Faulds D.
Adis International Limited, Auckland, New Zealand. demail@adis.co.nz
Raltitrexed (ZD-1694) is a quinazoline-based folate analogue that exerts its cytotoxic activity by the specific inhibition of thymidylate synthase. In vitro studies show that raltitrexed is actively transported into cells and is then rapidly and extensively metabolised to a series of polyglutamates. These metabolites are significantly more potent inhibitors of thymidylate synthase than the parent drug and are retained intracellularly, producing prolonged cytotoxic effects without the need for continuous drug exposure. Phase III clinical trials in patients with advanced colorectal cancer evaluated raltitrexed 3 mg/m2 administered as a 15-minute intravenous infusion once every 3 weeks. This schedule produced objective response rates of 14.3 to 19.3%, which were similar to those in patients treated with fluorouracil plus leucovorin (15.2 to 18.1%). Median survival durations ranged from 9.7 to 10.9 months with raltitrexed treatment and from 10.2 to 12.7 months with fluorouracil plus leucovorin. The major toxicities associated with raltitrexed involve the haematological and gastrointestinal systems, although severe asthenia also occurred in 6 to 18% of patients receiving the drug. Grade 3 or 4 nausea or vomiting occurred in up to 13% of raltitrexed recipients and grade 3 or 4 diarrhoea in up to 14%. Similar incidences of grade 3 or 4 nausea or vomiting and diarrhoea were seen with fluorouracil plus leucovorin treatment. Raltitrexed generally showed significant advantages over fluorouracil plus leucovorin with respect to the incidence of leucopenia and mucositis. A greater proportion of raltitrexed than fluorouracil plus leucovorin recipients were able to receive the scheduled dosage. Thus, with its similar efficacy to fluorouracil-based regimens, convenient administration schedule and favourable tolerability profile, raltitrexed provides clinicians with a worthwhile alternative to fluorouracil-based treatment for patients with advanced colorectal cancer.

A practical guide to the management of distal ulcerative colitis.

Year 1998
Ardizzone S. Porro GB.
Gastrointestinal Unit, L. Sacco University Hospital, Milan, Italy.
This article reviews the role of corticosteroids, sulfasalazine and mesalazine (5-aminosalicylic acid, mesalamine), immunosuppressive agents and alternative novel drugs for the treatment of distal ulcerative colitis. Short cycles of traditional, rectally administered corticosteroids (methylprednisolone, betamethasone, hydrocortisone) are effective for the treatment of mild to moderately active distal ulcerative colitis. In this context, their systemic administration is limited to patients who are refractory to either oral 5-amino-salicylates, topical mesalazine or topical corticosteroids. Of no value in maintaining remission, the long term use of either or topical corticosteroids may be hazardous. A new class of topically acting corticosteroids [budesonide, fluticasone, beclomethasone dipropionate, prednisolone-21-methasulphobenzoate, tixocortol (tixocortol pivalate)] represents a valid alternative for the treatment of active ulcerative colitis, and may be useful in the treatment of refractory distal ulcerative colitis. Although there is controversy concerning dosage or duration of therapy, oral and topical mesalazine is effective in the treatment of mild to moderately active distal ulcerative colitis. Sulfasalazine and mesalazine remain the first-choice drugs for the maintenance therapy of distal ulcerative colitis. Evidence exists showing a trend to a higher remission rate with higher doses of oral mesalazine. Topical mesalazine (suppositories or enemas) also is effective in maintenance treatment. For patients with chronically active or corticosteroid-dependent disease, azathioprine and mercaptopurine are effective in reducing either the need for corticosteroids or clinical relapses. Moreover, they are effective for long term maintenance remission. Cyclosporin may be useful in inducing remission in patients with acutely severe disease who do not achieve remission with an intensive intravenous regimen. Existing data suggest that azathioprine and mercaptopurine may be effective in prolonging remission in these patients. The role of alternative drugs for the treatment of distal ulcerative colitis and its different forms is reviewed. In particular data are reported concerning the effectiveness of 5-lipoxygenase inhibitors, topical use of short chain fatty acids, nicotine, local anaesthetics, bismuth subsalicylate enema, sucralfate, clonidine, free radical scavengers, heparin and hydroxychloroquine.

Diagnosis and treatment of Whipples disease.

Year 1998
Singer R.
Klinik fur Innere Medizin, Krankenhaus Speyerhof, Heidelberg, Germany.
Whipple's disease is a rare systemic infectious disease. To date, it has neither been possible to culture the bacillus Tropheryma whippelii, nor to infect other individuals with the pathogen. Today the diagnosis is confirmed by means of polymerase chain reaction (PCR) technology. Typically, the material for the PCR analysis comes from the duodenum. The diagnosis can also be established in this way on the basis of other tissue, or the cerebrospinal fluid. Treatment should only be carried out with antibiotics which cross into the cerebrospinal fluid, since there can also be an unrecognised involvement of the CNS. At present, the favoured method of treatment is the daily parenteral administration of 1.2 million units of benzylpenicillin (penicillin G) and streptomycin 1 g for a period of 2 weeks. This is followed by treatment with cotrimoxazole (trimethoprim 160 mg and sulfamethoxazole 800 mg) twice daily for 1 to 2 years. The treatment should begin and end with a PCR analysis of cerebrospinal fluid, in order to definitively diagnose infection of the CNS with Whipple's disease and to document the disappearance of the bacillus from the CNS.