Impact of genetic and non-genetic factors on clinical responses to prochlorperazine in oxycodone-treated cancer patients

Influence of cytochrome P450 genotype on the plasma disposition of prochlorperazine metabolites and their relationships with clinical responses in cancer patients

Background

Oral prochlorperazine, a dopamine D2 receptor antagonist, is largely metabolized to sulphoxide, 7-hydroxylate and N-desmethylate by cytochrome P450s (CYPs). This study evaluated the influence of CYP genotype on the plasma dispositions of prochlorperazine and its metabolites and their relationships with antiemetic efficacy and prolactin elevation in cancer patients.

Methods

Forty-eight cancer patients treated with oral prochlorperazine were enrolled. Plasma prochlorperazine and its metabolites concentrations and serum prolactin concentration were determined at 12 h after the evening dosing. The genotypes of CYP2C19, CYP2D6 and CYP3A5 and the incidences of nausea and vomiting were investigated.

Results

The plasma concentrations of the prochlorperazine metabolites were weakly correlated with that of the parent drug. The CYP genotypes did not affect the plasma concentrations of prochlorperazine and its metabolites. The plasma concentrations of prochlorperazine and its metabolites were not associated with the incidences of nausea and vomiting. The incidence of vomiting was significantly higher in females than in males. The serum prolactin concentration was weakly correlated with the plasma concentrations of prochlorperazine and its metabolites. The plasma concentrations of prochlorperazine metabolites rather than the parent drug had a weaker relation to serum prolactin concentration.

Conclusions

The CYP genotypes did not affect the plasma dispositions of prochlorperazine and its metabolites. The prochlorperazine metabolites did not have a strong effect on antiemetic efficacy, while they were slightly associated with prolactin secretion in cancer patients.

Efficacy of Prophylactic Treatment for Oxycodone-Induced Nausea and Vomiting Among Patients with Cancer Pain (POINT): A Randomized, Placebo-Controlled, Double-Blind Trial

BACKGROUND

Although opioid-induced nausea and vomiting (OINV) often result in analgesic undertreatment in patients with cancer, no randomized controlled trials have evaluated the efficacy of prophylactic antiemetics for preventing OINV. We conducted this randomized, placebo-controlled, double-blind trial to evaluate the efficacy and safety of prophylactic treatment with prochlorperazine for preventing OINV.

MATERIALS AND METHODS

Cancer patients who started to receive oral oxycodone were randomly assigned in a 1:1 ratio to receive either prochlorperazine 5 mg or placebo prophylactically, given three times daily for 5 days. The primary endpoint was the proportion of patients who had a complete response (CR) during the 120 hours of oxycodone treatment. CR was defined as no emetic episode and no use of rescue medication for nausea and vomiting during 5 days. Key secondary endpoints were the proportion of patients with emetic episodes, proportion of patients with moderate or severe nausea, quality of life, and proportion of treatment withdrawal.

RESULTS

From November 2013 through February 2016, a total of 120 patients were assigned to receive prochlorperazine (n = 60) or placebo (n = 60). There was no significant difference in CR rates (69.5% vs. 63.3%; p = .47) or any secondary endpoint between the groups. Patients who received prochlorperazine were more likely to experience severe somnolence (p = .048).

CONCLUSION

Routine use of prochlorperazine as a prophylactic antiemetic at the initiation of treatment with opioids is not recommended. Further research is needed to evaluate whether other antiemetics would be effective in preventing OINV in specific patient populations.

IMPLICATIONS FOR PRACTICE

Prophylactic prochlorperazine seems to be ineffective in preventing opioid-induced nausea and vomiting (OINV) and may cause adverse events such as somnolence. Routine use of prophylactic prochlorperazine at the initiation of treatment with opioids is not recommended. Further research is needed to evaluate whether other antiemetics would be effective in preventing OINV in specific patient populations.

Psychotropics and Male Reproduction

Psychotropic drugs, including antidepressants, antipsychotics, and anticonvulsants, all have negative effects on sexual function and semen quality. These adverse events vary among men and are less pronounced for some medications, allowing their effects to be managed to some extent. Use of specific serotonin reuptake inhibitors (SSRIs) is prevalent in men of reproductive age; and application to treat premature ejaculation increases the number of young men on SSRI therapy. Oxidative damage to sperm can result from prolonged residence in the male reproductive tract. The increase in ejaculatory latency seen with SSRIs likely underlies some of their negative effects on semen quality, including higher sperm DNA fragmentation, seen in all SSRIs evaluated thus far. These medications increase prolactin (PRL) levels in some men, and this is often credited with inhibitory effects on male reproduction; however, testosterone levels are generally normal, reducing the likelihood of direct HPG axis inhibition by PRL. The tricyclic antidepressants have also been shown to increase PRL levels in some studies but not in others. The exception is the tricyclic antidepressant clomipramine, which profoundly increases PRL levels and may depress semen quality. Other antidepressants modulating synaptic levels of serotonin, norepinephrine, and/or dopamine may have toxicity similar to SSRIs, but most have not been evaluated. In limited studies, norepinephrine-dopamine reuptake inhibitors (NDRIs) and serotonin agonist/reuptake inhibitors (SARIs) have had minimal effects on PRL levels and on sexual side effects. Antipsychotic medications increase PRL, decrease testosterone, and increase sexual side effects, including ejaculatory dysfunction. The greatest evidence is for chlorpromazine, haloperidol, reserpine, risperidone, and thioridazine, with less effects seen with aripiprazole and clozapine. Remarkably few studies have looked at antipsychotic effects on semen quality, and this is an important knowledge gap in reproductive pharmacology. Lithium increases PRL and LH levels and decreases testosterone although this is informed by few studies. The anticonvulsants, many used for other indications, generally decrease free or bioavailable testosterone with variable effects on the other reproductive hormones. Valproate, carbamazepine, oxcarbazepine, and levetiracetam decrease semen quality; other anticonvulsants have not been investigated for this adverse reaction. Studies are required evaluating endpoints of pregnancy and offspring health for psychotropic medications.

Endogenous opiates and behavior: 2014

This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants). This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants).

Prophylactic Use of Antiemetics for Prevention of Opioid-Induced Nausea and Vomiting: A Questionnaire Survey among Japanese Physicians

BACKGROUND

Antiemetics are being used both for the treatment and prophylaxis of opioid-induced nausea and vomiting (OINV) in clinical practice, despite the lack of evidence for the prophylactic benefit. Data regarding the actual status of prophylactic antiemetic use for OINV remain to be elucidated.

OBJECTIVE

The objective of this study was to evaluate the practice among Japanese physicians of the prophylactic use of antiemetics when starting opioids prescription for the prevention of opioid-induced nausea and vomiting.

METHODS

This questionnaire survey was targeted among physicians experienced in cancer pain treatment at two institutions of Japan (Nagoya University Hospital and Ichinomiya City Municipal Hospital). The questionnaire assessed the physicians' practice and beliefs regarding the prophylactic antiemetics prescription when they start opioids in patients with cancer pain.

RESULTS

Questionnaires were filled in and received from 112 physicians from two institutions. Eighty-two percent of physicians prescribed prophylactic antiemetics at the beginning of opioid prescription, and the most commonly prescribed drug for this purpose was prochlorperazine (88%).

CONCLUSION

Despite the lack of evidence, Japanese physicians commonly prescribe prophylactic antiemetics, most commonly prochlorperazine, for OINV. Prospective clinical trials are necessary to evaluate the efficacy of this practice.