A new class of antiemetics: the NK-1 receptor antagonists

The effect of Neurokinin-1 receptor antagonists on postoperative pain: A meta-analysis of randomized controlled trials

STUDY OBJECTIVE

Substance P is a neuropeptide with a pivotal role in pain transmission and modulation. Preclinical studies suggest that targeting substance P and inhibiting its receptor, neurokinin 1 (NK-1), is a potential avenue for pain relief. When translated into clinical settings, these preliminary findings yielded mixed results. This meta-analysis of randomized controlled trials (RCTs) aims to investigate whether a preemptive administration of NK-1 antagonists may reduce postoperative pain.

DESIGN

We searched PubMed, Cochrane and EMBASE from inception to January 3, 2025, for studies comparing NK-1 antagonists versus placebo or standard care that reported data on postoperative pain. The primary outcome was pain at two hours after surgery measured through a 0-10 numeric scale. Secondary outcomes were postoperative pain at 24 and at 48 h and postoperative morphine equivalent consumption.

SETTING

Hospitals.

MAIN RESULTS

The search strategies identified 13 RCTs with a total of 1959 patients. All studies reported a single preoperative administration of NK-1 antagonists. NK-1 antagonists reduced postoperative pain two hours (n = 8; MD -0.62; 95 % CI: -0.91, -0.32; P < 0.001; I2 = 0 %) and at 24 h (n = 9; MD -0.65; 95 % CI: -1.22, -0.09; P = 0.02; I2 = 86 %) but not 48 h after surgery. Morphine equivalent consumption was similar in the two groups.

CONCLUSIONS

Preoperative single-administration of NK-1 antagonists reduces postoperative pain. The observed pain reduction pattern is consistent with the pharmacokinetics (half-life 9-12 h) of these inhibitors and with data from preclinical studies.

Non-peptide NK1 receptor ligands based on the 4-phenylpyridine moiety

The quinoline nucleus of the previously described 4-phenylquinoline-3-carboxamides NK(1) receptor ligands 7 has been transformed into either substituted or azole-(i.e., triazole or tetrazole) fused pyridine moieties of compounds 9 and 10, respectively, in order to obtain NK(1) receptor ligands showing lower molecular weight or higher hydrophilicity. The program of molecular manipulations produced NK(1) receptor ligands showing affinity in the nanomolar range. In particular, 4-methyl-1-piperazinyl derivative 9j showed an IC(50) value of 4.8 nM and was proved to behave as a NK(1) antagonist blocking Sar(9)-SP-sulfone induced proliferation and migration of microvascular endothelial cells. Therefore, compound 9j has been labeled with [(11)C]CH(3)I (t(1/2)=20.4 min, β(+)=99.8%) starting from the corresponding des-methyl precursor 9i using with a radiochemical yield of about 10% (not decay corrected) and a specific radioactivity>1 Ci/μmol in order to be used as a radiotracer in next PET studies.

Substance P is responsible for physiological alterations such as increased chloride ion secretion and glucose malabsorption in cryptosporidiosis

Cryptosporidiosis, caused by the protozoan parasite Cryptosporidium, causes self-limited diarrhea in immunocompetent hosts and severe life-threatening diarrhea in AIDS patients. Highly active antiretroviral therapy has been used to effectively treat cryptosporiosis in some but not all AIDS patients. Therefore, there is an urgent need for innovative drugs to treat this disease. Cryptosporidium infection results in intestinal pathophysiological changes such as glucose malabsorption, increased chloride ion (Cl(-)) secretion, and epithelial barrier disruption, leading to disease pathogenesis. In order to develop tools to combat this opportunistic pathogen, it is vital to understand mediators involved in disease pathogenesis. Substance P (SP), a neuropeptide and pain transmitter, is located in the gastrointestinal tract. SP can cause Cl(-) secretion in human gastrointestinal explants. However, its role in cryptosporidiosis has not been fully studied. Jejunal samples from macaques before and after Cryptosporidium parvum infection were assayed for SP and SP receptor mRNA and protein levels by reverse transcription-PCR and by immunohistochemistry and enzyme-linked immunosorbent assay, respectively. The role of SP in pathophysiological alterations, such as Cl(-) secretion and glucose malabsorption, was studied using tissues derived from macaques infected with C. parvum by the Ussing chamber technique. SP and SP receptor mRNA and protein expression levels were increased in jejunal samples following C. parvum infection and were accompanied by increased basal ion secretion and glucose malabsorption. In vitro treatment of samples obtained from infected macaques with the SP receptor antagonist aprepitant (Emend; Merck, Whitehouse Station, NJ) completely reversed the increase in basal ion secretion and corrected the glucose malabsorption. Our findings raise the possibility of using SP receptor antagonists for the treatment of symptoms associated with cryptosporidiosis.

Pharmacological Prophylaxis and Management of Adult Postoperative/Postdischarge Nausea and Vomiting

Postoperative nausea and vomiting (PONV) is a relatively common complication that can adversely affect the quality of a patient's postoperative recovery. Factors to consider when determining a patient's risk for developing PONV include female gender, history of PONV, history of motion sickness, nonsmoking status, postoperative use of opioids, use of inhaled anesthetic agents, and use of nitrous oxide. Receptors that, when activated, can cause PONV include dopamine type-2, serotonin type-3, histamine type-1, muscarinic cholinergic type-1, and neurokinin type-1. Patients with a moderate-to-high risk of developing PONV will benefit from the administration of a prophylactic antiemetic agent that blocks one or more of these receptors. Effective agents for prophylaxis include transdermal scopolamine, prochlorperazine, promethazine, droperidol, ondansetron, dolasetron, granisetron, dexamethasone, and aprepitant. In the highest-risk patients, combining two or more prophylactic antiemetics with different mechanisms of action has been shown to be more effective than a single agent. In addition, the patient's risk could be reduced by considering the use of regional anesthesia, maintaining general anesthesia with propofol rather than with inhaled anesthetic agents, ensuring good intravenous hydration, and providing effective pain management using a multimodal approach (eg, minimizing the use of opioids). If PONV does occur in the immediate postoperative period, it is best treated with an antiemetic agent from a different pharmacologic class than the agent that was administered for prophylaxis. Once a patient is discharged, alternative formulations of antiemetics such as ondansetron oral or dissolving tablets or promethazine tablets or suppositories can be used.

Aprepitant for the control of chemotherapy induced nausea and vomiting in adolescents

Nausea and vomiting are common side effects of chemotherapy in adult and pediatric patients. Even with standard antiemetic therapy, a significant number of patients continue to experience acute and delayed symptoms. When used in combination with standard antiemetic therapy, a new class of antiemetics, the neurokinin-1 (NK-1) receptor antagonists, have been shown to improve both acute and delayed nausea and vomiting in adults. In this report, we describe the NK-1 receptor antagonist aprepitant in two adolescent patients receiving highly emetogenic chemotherapy who had experienced refractory nausea and vomiting with previous chemotherapy courses. The addition of aprepitant to the antiemetic regimen in the patients resulted in significant subjective improvement in nausea and vomiting as well as quality of life. These results in our adolescent patients are promising, but there is a need for well-designed studies to determine the efficacy, dosing, and safety of aprepitant in children of all ages.

Management of chemotherapy-induced nausea, vomiting, oral mucositis, and diarrhoea

The past 10 years have seen substantial advances in molecularly targeted therapies for treatment of patients with cancer; however, chemotherapy will continue to be used. Therefore, the toxic effects of chemotherapy must be readily managed-especially nausea, vomiting, mucositis, and diarrhoea. For moderately to highly emetogenic chemotherapy, standard prophylactic treatment is an antagonist for 5-hydroxytryptamine 3 receptors (5-HT3R) combined with dexamethasone for the acute phase, and dexamethasone with another agent for prevention of the delayed phase. Palonoestron (a 5-HT3R antagonist) and aprepitant (an antagonist for the protachykinin 1 receptor) have been introduced for the prevention of emesis. Other agents such as cannabinoids, gabapentin, and olanzapine might also be effective. There is no standard prophylactic regimen for chemotherapy-induced mucositis. The most common treatment is optimum care of the mouth by use of mouthwashes. Keratinocyte growth factor, molgromastim, and transforming growth factor beta3 may also reduce chemotherapy-induced mucositis. Severe diarrhoea is another potentially fatal complication of chemotherapy and is most common in patients treated with irinotecan. Several interventions have been assessed for prevention and treatment of diarrhoea such as high-dose loperamide, non-absorbable antibiotics, budesonide, thalidomide, and fish oils, but only loperamide is used routinely. Symptom management has become a focus of clinical research, and development of personalised medicine should identify patients at increased risk of toxic effects because of molecular or biochemical factors, thus leading to changes in dose, early intervention, or use of alternative therapies.

Chemotherapy-related nausea and vomiting - past reflections, present practice and future management

Although much progress has occurred in the last decade regarding the management of chemotherapy-induced nausea and vomiting, these remain among the most intolerable side-effects of treatment and patients continue to report the negative impact such symptoms have on their ability to enjoy life. Inadequate control of nausea and vomiting reduces patients' quality of life and functional status and jeopardizes the delivery of optimal treatment, so making its management a priority for oncology health care workers. This article will reflect on past and present evidence regarding the management of chemotherapy-induced nausea and vomiting while highlighting some of the most recent scientific advances before drawing conclusions about the future management of this troublesome symptom for patients receiving chemotherapy.

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.