Studies on hypersensitivity. IV. The relationship between contact and delayed sensitivity: a study of the specificity of cellular immune reactions

In earlier observations with the picryl system, it was concluded that contact sensitivity was a form of delayed (cellular) hypersensitivity to conjugates of sensitizer with autologous proteins indistinguishable in its immunological mechanism from other classical forms of delayed hypersensitivity to proteins. This conclusion has been confirmed and extended with the picryl and chlorbenzoyl chloride systems. 1. It is shown that to induce a state of contact sensitivity, the minimal necessary amounts of hapten are of the same order of magnitude, whether this hapten is conjugated with protein or the free reactive chemical itself. From this, it is evident that contamination of conjugates with small amounts of unreacted sensitizer plays no part in the induction of contact reactivity by the conjugate. With the dinitrophenyl system, no contact sensitivity could be induced by the conjugates used; possible reasons for this discrepancy are discussed. 2. Animals sensitized to contact by homologous conjugate can be completely desensitized by injections of such a conjugate in large amount; a similar injection schedule has no effect on the contact sensitivity of animals sensitized with the free reactive sensitizer. 3. The capacity of heterologous (ovalbumin) conjugates to evoke anti-hapten antibodies is shown to be greater than that of homologous (guinea pig seralbumin) conjugates: the reverse is true of their capacity to induce delayed reactivity. 4. Evidence is brought forward to suggest that in animals sensitized with homologous albumin conjugates, the specificity of the delayed reaction involves more than the hapten alone, even though the carrier protein is non-antigenic on its own. The contrast with the apparent lesser specificity of the antibodies later produced is discussed.

ANTI-EMETIC ACTIVITY OF PHENOTHIAZINES IN RELATION TO THEIR CHEMICAL STRUCTURE

Twelve phenothiazine derivatives have been studied for anti-emetic potency in dogs against emesis induced by apomorphine. The PD(50)s of all the compounds were determined and the activities compared with chlorpromazine hydrochloride as standard. Thioproperazine methanesulphonate was 300 times more active than chlorpromazine hydrochloride and twice as active as perphenazine sodium citrate. The anti-emetic activity of the compounds has been correlated with their chemical structure.

Metabolite kinetics of ondansetron in rat. Comparison of hepatic microsomes, isolated hepatocytes and liver slices, with in vivo disposition

1. The kinetics of hydroxylation and N-demethylation of ondansetron have been determined in freshly isolated hepatocytes, hepatic microsomes and precision-cut liver slices from the male Sprague-Dawley rat. In vivo studies have also been carried out to characterize the pharmacokinetics of ondansetron and in vitro data have been assessed for their value as predictors of hepatic clearance. 2. In the three in vitro systems, the formation of hydroxylated and demethylated metabolites were characterized as a function of substrate concentration by a high-affinity, low-capacity site and a low-affinity, high-capacity site which was not saturated over the concentration range studied (2.5-500 microM). Slices gave consistently higher Km's (20 and 30 microM for hydroxylation and demethylation respectively) than hepatocytes (3 and 13 microM respectively) and microsomes (2 and 5 microM respectively.) The rank order of Vmax and CL(int) was the same for each system; hydroxylation rates exceeding demethylation rates. Although two hydroxylations (7- and 8-hydroxy metabolites) occurred exclusively in microsomes, these are believed to originate from a common precursor. 3. The high CL(int) of ondansetron (150 ml/min/SRW, where SRW is a standard rat weight of 250g) is well predicted by scaling either microsomal clearance for microsomal protein recovery or hepatocyte clearance for hepatocellularity (212 and 135 ml/min/SRW respectively). In contrast, the use of liver slice data scaled to a whole liver substantially underestimates CL(int) (9 ml/min/SRW).

Clinical manifestations of transdermal scopolamine addiction

Transdermal scopolamine patches have been extensively prescribed for nonspecific dizziness and vestibular disorders. Patient response may be favorable and side effects are generally limited to xerostomia and blurred vision. However, subtle dependency and outright addiction may develop. Tapered reduction and drug elimination will suffice to eliminate the dependency. However, hospitalization may be necessary to treat severe cases of physiological chemical dependency. Long-term use of transdermal scopolamine patches carries a risk of chemical dependency. Prescribing physicians should review and heed the manufacturer's recommended use.

The pattern of emesis following high-dose cyclophosphamide and the anti-emetic efficacy of ondansetron

Two randomized, double-blind placebo-controlled ondansetron dose ranging studies in patients receiving high-dose cyclophosphamide (with or without doxorubicin) were completed in the US. These studies enable the pattern of emesis and nausea for 3 days following high-dose cyclophosphamide to be described and give some insight into the mechanisms of emesis which may be operating. Nausea and vomiting induced by cyclophosphamide-based chemotherapy has a long latency of onset (8-13 h) and continues for at least 3 days. These findings are of particular importance as many of these patients receive chemotherapy as outpatients and emphasize the need for appropriate anti-emetic prophylaxis for patients at home. Ondansetron was extremely effective over this time in the control of emesis and nausea. These results suggest that high-dose cyclophosphamide-induced emesis over days 1-3 is largely mediated via 5-hydroxytryptamine (5-HT) and 5-HT3 receptors.

A possible anti-emetic role for sodium valproate in cytotoxic chemotherapy

We report two patients with acute leukaemia who received emetogenic cytotoxic drugs and were on therapeutic doses of sodium valproate for epilepsy. Neither patient reported significant nausea nor vomited at any time during the chemotherapy, at times requiring no anti-emetic treatment whatsoever. We suggest that this absence of nausea was due to an anti-emetic effect of sodium valproate.

Prophylactic antiemetic therapy with patient-controlled analgesia: a double-blind, placebo-controlled comparison of droperidol, metoclopramide, and tropisetron

This placebo-controlled, randomized, double-blind trial was designed to evaluate the efficacy of three prophylactic antiemetic regimens on postoperative nausea and vomiting (PONV) during patient-controlled analgesia (PCA) with morphine. We studied 286 elective surgical patients for 36 h postoperatively. Group 1 was saline control. In Groups 2 and 3, metoclopramide or droperidol was administered as an intravenous (i.v.) bolus and then added to morphine in the PCA device. In Group 4, tropisetron, a long-acting investigational 5-hydroxytryptamine subtype 3 (5-HT3) antagonist was given as a single i.v. dose. We assessed the frequency and severity of PONV, as well as the need for rescue, frequency of side effects, and overall patient satisfaction. Severity of PONV was measured with a symptom-severity score (STS) which was based on both intensity and duration. The average total doses of antiemetics were metoclopramide 53.8 +/- 2.2 mg, droperidol 5.99 +/- 0.3 mg, and tropisetron 6.1 +/- 0.2 mg. Control patients had a 54% incidence of PONV. Droperidol reduced both the incidence (P < 0.001) and severity (P < 0.01) of PONV for the entire 36 h. Tropisetron reduced incidence and severity (P < 0.05), but the effect of the single bolus dose lasted only 18 h. Metoclopramide had a marginally significant effect under these conditions. Only droperidol decreased the need for rescue medication (P < 0.01), although rescue with tropisetron was highly effective. Side effects and patient satisfaction were comparable among the groups, but patients receiving droperidol were sleepier (P < 0.05) than control patients and recalled somewhat more anxiety (P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Endogenous cortisol exerts antiemetic effect similar to that of exogenous corticosteroids

Lower pre-chemotherapy night time cortisol excretion predicted more severe cisplatin induced nausea and vomiting in 42 ovarian cancer patients receiving ondansetron as a single antiemetic agent. Dexamethasone administration added to the antiemetic effect of ondansetron principally in patients who had low excretion of cortisol.

Mechanism of the anti-emetic activity of 5-HT3 receptor antagonists

Ondansetron, a potent and highly selective 5-HT3 receptor antagonist, prevents emesis following chemotherapy by antagonising the action of 5-hydroxytryptamine (5-HT) at 5-HT3 receptors on vagal afferent neurons that innervate the gastrointestinal tract and 5-HT3 receptors in the central vomiting system. Evidence suggests that chemotherapy induces the release of 5-HT from enterochromaffin cells in the small intestine. This stimulates vagal afferent nerves via 5-HT3 receptors. Information is then relayed, via the vagus nerve, to the central vomiting system. 5-HT3 receptors are also found in the hind-brain vomiting system including the area postrema (the site of the chemoreceptor trigger zone for emesis). Therefore, following chemotherapy, 5-HT activates 5-HT3 receptors at 2 sites to induce emesis. Clinical data showing that a single dose of ondansetron prevents acute emesis suggest that it is important to block the initiation of the emetic reflex. This may prevent the recruitment of central mechanisms involving 5-HT3 receptors.

Serotonin antagonists: a new class of antiemetic agents

Despite a number of significant advances over the past decade, prevention and treatment of chemotherapy-induced emesis remain formidable problems, particularly with cisplatin-containing regimens. Nearly one third of patients receiving high-dose cisplatin still experience substantial emesis despite the best available conventional antiemetics, and the toxic effects of these agents remain quite troublesome. In recent years, a new class of agents, the serotonin antagonists, has been identified. These agents hold promise for clinical utility in a wide range of areas. Selective antagonists of the serotonin (5-hydroxytryptamine) type 3 (5-HT3) receptor have proven in early clinical trials to be potent antiemetic agents in patients receiving cytotoxic chemotherapy, with efficacy comparable to or superior to that of conventional antiemetics. Toxic effects to date with the 5-HT3 receptor antagonists have been modest. The current state of knowledge with respect to these agents as antiemetics for patients receiving cytotoxic chemotherapy is summarized.

[Usefulness of alprazolam in controlling cisplatin-induced emesis]

Usefulness of alprazolam for control of chemotherapy-induced emesis including 5-day continuous intravenous infusion of cisplatin for advanced lung cancer was evaluated by a randomized crossover design. Of 22 cases evaluated, 8 in the alprazolam group and 1 in the untreated group were free from nausea and vomiting (p less than 0.01). The mean frequency of vomiting in the alprazolam group was 1.18 times, which is significantly smaller than 2.25 times in the untreated group (p less than 0.05). The mean duration of vomiting and nausea was significantly shorter in the alprazolam group (p less than 0.01, p less than 0.05). It is thus concluded that concomitant therapy with the minor tranquilizer alprazolam is useful in treating cisplatin-induced acute or delayed emesis in which psychological and psychiatric factors are involved.

Studies on the emetic and antiemetic properties of zacopride and its enantiomers

In ferrets, the oral emetic activity of zacopride was compared with its R- and S-enantiomers. Increasing doses of 0.01, 0.1, 1.0, 10.0 and 31.6 mg/kg of zacopride or its 2 enantiomers were each administered at hourly intervals to separate groups of animals until emesis occurred. The emetic (100%) dose for zacopride and its S-enantiomer was 0.11 mg/kg p.o. (cumulative dose). The R-enantiomer at a cumulative dose of 42.71 mg/kg p.o. produced emesis in 25% of the animals. By the i.p. route zacopride and its S-enantiomer were more potent than the R-enantiomer in blocking the emetic activity of 0.1 mg/kg p.o. of zacopride. The involvement of 5-HT3 mechanisms is indicated by a correlation between zacopride and its enantiomers to cause and prevent emesis and their affinity at 5-HT3 binding sites. Further, the putative 5-HT3 agonists, 2-methyserotonin and phenylbiguanide, at 10 mg/kg p.o., produced emesis that was blocked by zacopride (0.1 mg/kg i.p.) or ICS 205-930 (1 mg/kg i.p.). The results suggest that in the ferret the S-enantiomer is predominantly responsible for both the emetic and antiemetic properties of zacopride and that 5-HT3 agonism and antagonism are involved in these actions.

Single-dose i.v. dexamethasone--an effective anti-emetic in cancer chemotherapy

We conducted a randomised, single-blind, placebo-controlled crossover study to assess the efficacy of a single i.v. dose of 20 mg dexamethasone as an anti-emetic in 31 patients receiving cancer chemotherapy. Patients receiving dexamethasone experienced significantly less nausea and vomiting (P less than 0.001 and P less than 0.01, respectively), and appetite and activity were normal in a majority of the treated group. Side effects were insignificant. We conclude that single-dose dexamethasone given i.v. at a dose of 20 mg is a safe and effective anti-emetic for patients receiving cancer chemotherapy excluding cisplatin.

The antiemetic efficacy of thiethylperazine and methylprednisolone versus thiethylperazine and placebo in breast cancer patients treated with adjuvant chemotherapy (fluorouracil, doxorubicin and cyclophosphamide). A randomized, double-blind, cross-over trial

Forty-six women with breast cancer treated with adjuvant FAC (fluorouracil, doxorubicin and cyclophosphamide) entered a multicenter, randomized, double-blind, cross-over trial in which thiethylperazine (T) (6.5 mg p.o every 8 h x 3 days) plus methylprednisolone (MP) (250 mg i.v. x 2 doses) was compared with thiethylperazine plus placebo. Forty-four patients were evaluable for efficacy. T + MP was significantly better in reducing vomiting (p less than 0.01) and nausea (p less than 0.02). The complete protection rate against vomiting was 36% for T + MP compared to 18% for T + placebo, and the percentage of nausea grades 0 + 1 (none or slight) was 59% and 27% respectively. The patient preference after cross-over was strikingly in favor of T + MP (70% versus 13%) (p less than 0.001). The most important side-effects of T + MP were facial flushing (22%) and euphoria (27%). Other side-effects, such as dryness of the mouth and sedation, were common after both treatments. In conclusion, the study suggested that T + MP is superior to T alone in protecting from nausea and vomiting induced by FAC.