Pharmacokinetic profile and clinical efficacy of a once-daily ondansetron suppository in cyclophosphamide-induced emesis: a double blind comparative study with ondansetron tablets

Inhibition of Small-Conductance, Ca2+-Activated K+ Current by Ondansetron

Background: Small-conductance Ca²⁺-activated K⁺ channels (SK channels) have been proposed as antiarrhythmic targets for the treatment of atrial fibrillation. We previously demonstrated that the 5-HT₃ receptor antagonist ondansetron inhibits heterologously expressed, human SK2 (hSK2) currents as well as native cardiac SK currents in a physiological extra-/intracellular [K⁺] gradient at therapeutic (i.e., sub-micromolar) concentrations. A recent study, using symmetrical [K⁺] conditions, challenged this result. The goal of the present study was to revisit the inhibitory effect of ondansetron on hSK2-mediated currents in symmetrical [K⁺] conditions.

Experimental Approach: The whole-cell patch clamp technique was used to investigate the effects of ondansetron and apamin on hSK2-mediated currents expressed in HEK 293 cells. Currents were measured in symmetrical [K⁺] conditions in the presence of 100 nM [Ca²⁺]_o.

Results: Expression of hSK2 produced inwardly rectifying whole-cell currents in the presence of 400 nM free cytosolic Ca²⁺. Ondansetron inhibited whole-cell hSK2 currents with IC₅₀ values of 154 and 113 nM at −80 and 40 mV, respectively. Macroscopic current inhibited by ondansetron and current inhibited by apamin exhibited inwardly rectifying current-voltage relationships with similar reversal potentials (apamin, ∼5 mV and ondansetron, ∼2 mV). Ondansetron (1 μM) in the continuing presence of apamin (100 nM) had no effect on hSK2-mediated whole-cell currents. Wild-type HEK 293 cells did not express ondansetron- or apamin-sensitive currents.

Conclusion: Ondansetron in sub-micromolar concentrations inhibits hSK2 currents even under altered ionic conditions.

Flavored Intravenous Ondansetron Administered Orally for the Treatment of Persistent Vomiting in Children

OBJECTIVE

To study the serum level of ondansetron after oral administration of intravenous ondansetron, and test the palatability of the drug after being flavored.

METHOD

This is a single-center prospective study enrolling children aged 3-8 years with gastroenteritis treated for persistent vomiting; patients received single dose of flavored intravenous ondansetron orally. The primary outcome was ondansetron serum level at 4 hours. Secondary outcome was palatability of the drug.

RESULTS

Forty previously healthy patients presenting with acute gastroenteritis were enrolled. The mean age was 4.86±1.37 years. Serum level at 4 h had a median of 26.23 ng/ml, range (8.3-52 ng/ml). Palatability of the drug had a mean of 3.23 (of 5) ± 0.80, based on score from visual analog scale.

CONCLUSIONS

Flavored intravenous ondansetron administered orally is a safe and an effective option and can be considered in the absence of the oral forms of the drug.

Design and evaluation of ondansetron liquid suppository for the treatment of emesis

The thermosensitive-mucoadhesive ondansetron liquid suppository (tmOLS) was developed to enhance patient compliance and bioavailability in high-risk patients receiving highly emetogenic therapy and having difficulty in swallowing, The thermosensitive-mucoadhesive liquid suppository bases were formulated using poloxamers (P407 and P188) and hydroxypropylmethyl cellulose (HPMC). The physicochemical properties of the liquid suppository bases were characterized by their gelation temperature, mucoadhesive force, rheological properties, and in vitro release. Rectal mucosal damage following rectal administration of tmOLS in rats was assessed using microscopy. Pharmacokinetic analyses were performed to compare tmOLS administered via the rectal route to ondansetron solution administered orally. The liquid suppository base of tmOLS contained P407, P188, and HPMC in the ratio 18:20:0.8, was in the liquid state at room temperature, underwent gelation at body temperature. Area under the curve and half-life (t1/2) of ondansetron were significantly higher in the tmOLS-treated group, indicating that the formulation bypassed the first-pass metabolism and that it was released slowly from the tmOLS because of the formation of mucoadhesive gel state. Furthermore, the t1/2 of tmOLS was two-fold that of the oral solution. Thus, tmOLS could be administered to patients who have difficulty in swallowing; however, adjustments in dosing interval may be needed.

[Management of chemotherapy-induced emesis: what is the standard after 20 years of clinical research]

BACKGROUND

The knowledge of the importance, the physiopathological mechanisms, and the management of the chemotherapy-induced emesis has increased exponentially during the last 20 years. High-dosage metoclopramide (MCP) therapy has been introduced in the eighties and serotonine type-3 receptor antagonists (5-HT(3) antagonists) have been used since the late eighties and early nineties. Due to both classes of substances the results of the antiemetic therapies have improved drastically. After 20 years of intensive clinical research it seems to be appropriate to come to an intermediate conclusion.

METHOD

With the aid of an overview and a new analysis of the literature published on this topic so far, the current state of research is shown (including the fields in which further improvement will be necessary), and suggestions are made, wherever it seemed possible, to attain the "gold standard" in antiemetic therapy.

RESULTS AND CONCLUSIONS

In connection with all highly or very highly emetogenic chemotherapies, an antiemetic prophylaxis should be initiated on the day of therapy, especially when using platinum or most of the cyclophosphamide-based regimes for cancer treatment. The recommended prophylaxis consists of a combination of 5-HT(3) antagonists with a corticosteroid. To combat the so-called delayed emesis on the days following therapy, all patients should undergo an oral corticoid therapy, possibly in combination with MCP (especially platinum-therapy patients), less frequently with 5-HT(3) antagonists. With these means of prophylaxis emesis can be prevented/avoided completely in most patients, and nausea can at least be reduced. It is sufficient to administer a single dose of 5-HT(3) antagonists prior to chemotherapy. For ondansetron and granisetron, the best documented substances within this class of drugs, 8 mg (ondansteron) and 3 mg (granisetron) are considered standard dosages. Among the corticoids, most data have been accumulated for dexamethasone. A standard dose of 10 to 20 mg can be administered prior to chemotherapy. Right after and especially on the days following chemotherapy higher dosages seem to be indicated.

PROSPECT

Further therapy improvements, especially concerning emesis and nausea on the days following chemotherapy, are necessary and are currently object of clinical research.

A pharmacokinetic interaction study of docetaxel and cisplatin plus or minus 5-fluorouracil in the treatment of patients with recurrent or metastatic solid tumors

BACKGROUND

The purpose of this study was to look at the pharmacokinetics of docetaxel, cisplatin-derived platinum and 5-fluorouracil (5-FU), when used in combination, to exclude potential clinically relevant pharmacokinetic interactions.

METHODS

Fifteen patients with recurrent or metastatic solid tumors were randomized to receive docetaxel 75 mg/m2 and cisplatin 75 mg/m2 in the first treatment course on day 1 and the same combination plus 5-FU 750 mg/m2/day on days 1-5 in the second course, or the two treatment courses in reversed order. Cycles were repeated every 3 weeks. A pharmacokinetic analysis was performed during the first two cycles.

RESULTS

Full pharmacokinetic data was available for 12 of the 15 patients. Treatment was tolerated well, with frequency of toxicity consistent with the safety profile known for docetaxel, cisplatin and 5-FU. Mean clearance values for docetaxel and cisplatin showed no statistically significant difference across the "triple" and the "double" combination treatments, and the mean pharmacokinetic parameters of all agents were within the ranges for previously reported single agent treatment.

CONCLUSION

No clinically relevant pharmacokinetic interactions between docetaxel, cisplatin and 5-FU used in combination were noticed in this study.

Anti-emetics for cancer chemotherapy-induced emesis: Potential of alternative delivery systems

Currently, the most commonly used routes of administration of antiemetics in chemotherapeutic regimens are oral and intravenous. Patient compliance and thus efficacy of conventional drug schedules and formulations are often impaired by difficulties associated with oral or intravenous uptake of the administered chemotherapy. Alternative or new drug delivery systems should overcome these problems by improving patient compliance. Several new drug delivery systems are available and development of these new systems is ongoing, in particular to meet delivery requirements of modern biological therapeutics and the application of gene therapy. However, at the present time, the implementation of new techniques of alternative antiemetic drug administration for chemotherapy-induced emesis is very limited. The challenge for clinical investigations to further develop new delivery systems, in particular for antiemetic therapies, remains.