Multiple receptors contribute to the behavioral effects of indoleamine hallucinogens

Serotonergic hallucinogens produce profound changes in perception, mood, and cognition. These drugs include phenylalkylamines such as mescaline and 2,5-dimethoxy-4-methylamphetamine (DOM), and indoleamines such as (+)-lysergic acid diethylamide (LSD) and psilocybin. Despite their differences in chemical structure, the two classes of hallucinogens produce remarkably similar subjective effects in humans, and induce cross-tolerance. The phenylalkylamine hallucinogens are selective 5-HT(2) receptor agonists, whereas the indoleamines are relatively non-selective for serotonin (5-HT) receptors. There is extensive evidence, from both animal and human studies, that the characteristic effects of hallucinogens are mediated by interactions with the 5-HT(2A) receptor. Nevertheless, there is also evidence that interactions with other receptor sites contribute to the psychopharmacological and behavioral effects of the indoleamine hallucinogens. This article reviews the evidence demonstrating that the effects of indoleamine hallucinogens in a variety of animal behavioral paradigms are mediated by both 5-HT(2) and non-5-HT(2) receptors.

Effects of exposure to selective serotonin reuptake inhibitors during pregnancy on serotonergic symptoms in newborns and cord blood monoamine and prolactin concentrations

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) have gained wide acceptance in the treatment of mental disorders in pregnant women, but there seems to be an increased risk for neonatal adaptation problems after exposure to SSRIs in late pregnancy. We aimed to investigate the perinatal sequelae of infants exposed to SSRIs during their fetal life and the relationship of these symptoms to the cord blood monoamine and prolactin concentrations.

METHODS

We conducted a prospective, controlled, follow-up study with 20 mothers taking 20 to 40 mg/d of either citalopram or fluoxetine for depression (n = 10) or panic disorder (n = 10) and their infants and 20 matched controls not receiving psychotropic medication for confounding obstetric characteristics. Maternal cord blood and infant citalopram, fluoxetine, and norfluoxetine, cord blood monoamine and metabolite, and prolactin concentrations were measured. The newborns underwent standard clinical examination and specific assessment of serotonergic symptoms during the first 4 days of life and at the ages of 2 weeks and 2 months.

RESULTS

There was a statistically significant (P =.008, V = 15, n = 20 for both groups), 4-fold difference in the serotonergic symptom score during the first 4 days of life between the SSRI group and the control group. The SSRI-exposed infants had significantly lower cord blood 5-hydroxyindoleacetic acid (5-HIAA) concentrations (P =.02, t31 = 2.57) compared with the control group. A significant inverse correlation (rs = -0.66, P =.007, n = 15) was seen between the serotonergic symptom score and the umbilical vein 5-HIAA concentrations in the SSRI-exposed but not the control infants.

CONCLUSIONS

Infants exposed to SSRIs during late pregnancy are at increased risk for serotonergic central nervous system adverse effects, and the severity of these symptoms is significantly related to cord blood 5-HIAA levels.

Adverse effects of opioid agonists and agonist-antagonists in anaesthesia

The traditional view of opioids held that the individual opioid agonists shared the same mechanism of action, differing only in their potency and pharmacokinetic properties. However, recent advances in opioid receptor pharmacology have made this view obsolete. Distinguishing features of the synthetic opioid agonists are related, at least in part, to variation in affinity and intrinsic efficacy at multiple opioid receptors. Respiratory depression is the opioid adverse effect most feared by anaesthesiologists. Specific kappa-receptor agonists produce analgesia with little or no respiratory depression. There are a number of commercially available kappa-receptor partial agonist drugs, the so-called agonist-antagonist or nalorphine-like opioids, which appear to have a limited effect on breathing. Within the series of fentanyl analogues there are differences in behaviour towards particular opioid receptors and there is evidence for subtle differences in respiratory depressant effects. Pethidine (meperidine) causes histamine release and myocardial depression, while the fentanyl analogues do not. Pethidine has atropine-like effects on heart rate, while fentanyl analogues reduce heart rate by a vagomimetic action. Severe bradycardia or even asystole is possible with fentanyl analogues, especially in conjunction with the vagal stimulating effects of laryngoscopy. Fentanyl analogues often produce minor reductions in blood pressure, and occasionally severe hypotension by centrally mediated reduction in systemic vascular resistance. Muscle rigidity and myoclonic movement occurs frequently during induction of anaesthesia with larger doses of opioids. Fentanyl and alfentanil have been reported to produce localised temporal lobe electrical seizure activity in patients with complex partial epilepsy. There are probably fewer biliary effects with agonist-antagonist opioids than the agonist opioids. The mechanism of adverse effects after spinal administration is distinctly different for morphine, which is very water soluble, compared with more lipid-soluble opioids. The systemic absorption of morphine after intrathecal or epidural administration is very slow, resulting in long duration of analgesia and low plasma concentrations, while lipid-soluble opioids are rapidly absorbed into the circulation and redistributed to the brain. The serotonin syndrome may result from coadministration of pethidine, dextromethorphan, pentazocine or tramadol with monoamine oxidase inhibitors (MAOIs) or selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs). There are clinically important interactions between opioids and hypnosedatives, resulting in synergistic effects on sedation, breathing and blood pressure.

A review of serotonin toxicity data: implications for the mechanisms of antidepressant drug action

Data now exist from which an accurate definition for serotonin toxicity (ST), or serotonin syndrome, has been developed; this has also lead to precise, validated decision rules for diagnosis. The spectrum concept formulates ST as a continuum of serotonergic effects, mediated by the degree of elevation of intrasynaptic serotonin. This progresses from side effects through to toxicity; the concept emphasizes that it is a form of poisoning, not an idiosyncratic reaction. Observations of the degree of ST precipitated by overdoses of different classes of drugs can elucidate mechanisms and potency of drug actions. There is now sufficient pharmacological data on some drugs to enable a prediction of which ones will be at risk of precipitating ST, either by themselves or in combinations with other drugs. This indicates that some antidepressant drugs, presently thought to have serotonergic effects in animals, do not exhibit such effects in humans. Mirtazapine is unable to precipitate serotonin toxicity in overdose or to cause serotonin toxicity when mixed with monoamine oxidase inhibitors, and moclobemide is unable to precipitate serotonin toxicity in overdose. Tricyclic antidepressants (other than clomipramine and imipramine) do not precipitate serotonin toxicity and might not elevate serotonin or have a dual action, as has been assumed.

Linezolid-associated peripheral and optic neuropathy, lactic acidosis, and serotonin syndrome

Linezolid is an oxazolidinone antibacterial agent indicated for serious gram-positive infections. Only minor adverse effects were seen in phase III trials. However, more serious adverse effects were reported after commercial release, including cases of lactic acidosis, peripheral and optic neuropathy, and serotonin syndrome. Peripheral and optic neuropathy was usually seen after several months of linezolid therapy (median 5 mo), lactic acidosis after several weeks (median 6 wks), and serotonin syndrome after several days (median 4 days). Death occurred in two of seven reported cases of lactic acidosis, and three of 15 reported cases of serotonin syndrome. Improvement or complete recovery occurred in all cases of optic neuropathy, whereas complete recovery failed to occur in any patient with peripheral neuropathy. Linezolid should be discontinued immediately in patients experiencing these adverse effects. Patients receiving linezolid for more than 28 days should be monitored for signs of peripheral and optic neuropathy.

Linezolid and Serotonergic Drug Interactions: A Retrospective Survey

BACKGROUND

Linezolid is a reversible, nonselective monoamine oxidase inhibitor. There are currently 11 published case reports of serotonin syndrome being associated with linezolid and selective serotonin reuptake inhibitors (SSRIs). Controversy exists regarding whether linezolid and SSRIs can be given concomitantly. The purpose of this study was to report the incidence of serotonin syndrome in patients receiving linezolid and SSRIs.

METHODS

This study was a retrospective chart review of inpatients at the Mayo Clinic (Rochester, MN) with concomitant orders or therapy within 14 days for linezolid and an SSRI from 2000 to 2004. The Sternbach criteria and Boyer criteria for diagnosis of serotonin syndrome were used to identify clinical features of serotonin syndrome.

RESULTS

Seventy-two patients received linezolid and an SSRI or venlafaxine within 14 days of each other. Fifty-two patients (72%) received concomitant therapy with linezolid and an SSRI or venlafaxine, and 20 patients (28%) did not receive concomitant therapy but received linezolid and an SSRI within a 14-day period. Overall, only 2 patients (3%) had a high probability of serotonin syndrome. In both patients with high probability, symptoms reversed rapidly on discontinuation of serotonergic therapy. The Boyer criteria were much more specific than the Sternbach criteria for identification of serotonin syndrome.

CONCLUSIONS

On the basis of our experience, we suggest that, if the clinical situation warrants use of linezolid in a patient receiving an SSRI, linezolid may be used concomitantly with SSRIs, without a 14-day washout period and with careful monitoring for signs and symptoms of serotonin syndrome. Serotonergic agents should be promptly discontinued if serotonin syndrome is suspected.

Potent serotonin (5-HT)(2A) receptor antagonists completely prevent the development of hyperthermia in an animal model of the 5-HT syndrome

The serotonin (5-HT) syndrome is the most serious side effect of antidepressants, and it often necessitates pharmacotherapy. In the present study, the efficacy of several drugs was evaluated in an animal model of the 5-HT syndrome. When 2 mg/kg of clorgyline, a type-A monoamine oxidase inhibiting antidepressant, and 100 mg/kg of 5-hydroxy-L-tryptophan, a precursor of 5-HT, were administered intraperitoneally to rats to induce the 5-HT syndrome, the rectal temperature of the rats increased to more than 40 degrees C, and all of the animals died by 90 min after the drug administration. The noradrenaline (NA) levels in the anterior hypothalamus, measured by microdialysis, increased to 15.9 times the preadministration level. Pretreatment with propranolol (10 mg/kg), a 5-HT(1A) receptor antagonist as well as a beta-blocker, and dantrolene (20 mg/kg), a peripheral muscle relaxant, did not prevent the death of the animals, even though these two drugs suppressed the increase in rectal temperature to some extent. Chlorpromazine and cyproheptadine prevented the lethality associated with the 5-HT syndrome only at high doses. By contrast, pretreatment with ritanserin (3 mg/kg) and pipamperone (20 mg/kg), both potent 5-HT(2A) receptor antagonists, completely prevented the increase in rectal temperature and death of the animals, and the hypothalamic NA levels in these two groups increased less than that in the other groups. These results suggest that potent 5-HT(2A) receptor antagonists are the most effective drugs for treatment of the 5-HT syndrome, and that NA hyperactivity occurs in the 5-HT syndrome.

Serotonin syndrome and linezolid

We present a case of serotonin syndrome in a patient who initiated linezolid therapy shortly after discontinuation of therapy with a selective serotonin reuptake inhibitor (paroxetine).

Serotonin Syndrome Resulting from Coadministration of Tramadol, Venlafaxine, and Mirtazapine

OBJECTIVE

To report a case of serotonin syndrome (SS) resulting from the addition of tramadol to a medication regimen of venlafaxine and mirtazapine.

CASE SUMMARY

A 47-year-old white man receiving combined mirtazapine and venlafaxine therapy for major depressive disorder developed agitation, confusion, severe shivering, diaphoresis, myoclonus, hyperreflexia, mydriasis, tachycardia, and fever on coadministration of tramadol for chronic pain. An objective causality assessment revealed that the addition of tramadol was the probable cause of the adverse reaction.

DISCUSSION

SS is a potentially fatal iatrogenic complication of serotonergic polypharmacy. Considered idiopathic in presentation, it typically appears after initiation or dose escalation of the offending agent to a regimen including other serotonergic agents. All drugs that directly or indirectly increase central serotonin neurotransmission at postsynaptic 5-HT1A and 5-HT2A receptors can produce SS. Individual vulnerability appears to play a role in the development of SS. It is likely that the activation of 5-HT1A receptors by mirtazapine, the combined serotonin reuptake inhibition by venlafaxine and tramadol, as well as possible serotonin release by tramadol, contributed to the development of SS in this case.

CONCLUSION

It is vital that clinicians are aware of the potential for SS when psychotropic and nonpsychotropic agents are coadministered to certain patients, such as those with both depression and chronic pain.

Death following ingestion of MDMA (ecstasy) and moclobemide

Four deaths following the ingestion of moclobemide and MDMA ('ecstasy') are described. The probable cause of death in each case was serotonin syndrome as a result of an interaction between the two drugs. As none of the victims had been prescribed moclobemide it seems that each had taken the drug to enhance the effects of MDMA, with fatal consequences. Warnings are needed against misinformed attempts to potentiate the pharmacological effects of illicit drugs.

Serotonin syndrome after concomitant treatment with linezolid and citalopram

Linezolid, a new synthetic antimicrobial, is an important weapon against methicillin-resistant Staphylococcus aureus (MRSA). Although there are reports of serotonin syndrome developing after concomitant use of linezolid and the selective serotonin reuptake inhibitor paroxitene, this report concerns a patient receiving citalopram who developed thrombocytopenia, serotonin syndrome, and lactic acidosis and died following long-term linezolid therapy.

Serotonin syndrome in HIV-infected individuals receiving antiretroviral therapy and fluoxetine

OBJECTIVE

To describe HIV-infected individuals taking antidepressants who developed the serotonin syndrome due to drug--drug or drug--food interactions.

DESIGN AND SETTING

Case studies carried out at the HIV Outpatient Clinic, Atlanta Veterans Affairs Medical Center.

PARTICIPANTS AND INTERVENTIONS

HIV-positive patients who were receiving antiretroviral and antidepressant therapies and presented with symptoms consistent with the serotonin syndrome. Their antidepressants were discontinued or the doses reduced in order to resolve the symptoms.

RESULTS

Five cases of serotonin syndrome developed after patients who were taking antidepressants ingested P450 inhibitors.

CONCLUSIONS

Serotonin syndrome should be suspected in patients on serotonergic medications who present with mental status change, autonomic dysfunction, and neuromuscular abnormalities. Suspicion should be heightened in those who are ingesting substances known to inhibit P450 enzymes, such as protease inhibitors, non-nucleoside reverse transcriptase inhibitors, and grapefruit juice.

Tramadol: Understanding the Risk of Serotonin Syndrome and Seizures

Tramadol is commonly prescribed for pain control because it presents a lower risk for addiction and respiratory depression compared to other opioids. However, tramadol's serotonin and norepinephrine reuptake inhibitory effects result in a unique adverse effect profile. Two such adverse events are serotonin syndrome and seizures. The prevalence of tramadol-induced serotonin syndrome and seizures is modest in the general population, but if left untreated, the morbidity and mortality can be high; therefore, prompt recognition and management is essential. Various risk factors such as medical comorbidities, use or abuse of supratherapeutic doses of tramadol, and concomitant administration of proconvulsant serotonergic cytochrome P-450 inhibitors will help clinicians identify individuals at an elevated risk for serotonin toxicity and seizures. Serotonin syndrome and seizures can be effectively treated by administering benzodiazepines, providing supportive care, and discontinuing tramadol and other contributing agents. Cyproheptadine should be administered in moderate to severe cases of serotonin syndrome. Our objective is to summarize the literature on the pharmacology, epidemiology, risk factors, clinical presentations, and evidence-based management of tramadol-related seizures and serotonin syndrome.

Ayahuasca preparations and serotonin reuptake inhibitors: a potential combination for severe adverse interactions

The Amazonian psychoactive plant beverage ayahuasca has attracted increasing interest in recent years. Little attention has been given, however, to potentially dangerous interactions with other drugs. In particular, the interaction between the potent monoamine oxidase-inhibiting harmala alkaloids in ayahuasca and the selective serotonin reuptake inhibitor (SSRI) class of antidepressants may induce a serotonin syndrome with potentially grave outcome. Caution is advised when combining ayahuasca with certain pharmaceutical drugs.

Movement disorder emergencies

Movement disorders may present acutely, and failure to recognize and exclude important differential diagnoses can result in significant morbidity or mortality. Unfortunately, much of the literature pertaining to this topic is scattered and not easily accessible. This review aims to address this deficit. Movement disorder emergencies are discussed according to their most likely mode of presentation. Diagnostic considerations and early management principles are reviewed, along with appropriate pathophysiology where relevant.

Serotonin syndrome: early management with cyproheptadine

OBJECTIVE

To report a psychiatric patient who developed serotonin syndrome after a medication overdose and whose marked mydriasis was quickly reversed by administration of cyproheptadine. This phenomenon was confirmed when other cases of serotonin syndrome were studied.

METHOD

In the index patient as well as in three subsequent cases of serotonin syndrome, pupil diameter, muscle tone, mental status, and vital signs were monitored before and after a test dose of cyproheptadine as medications were discontinued and antiserotonergic therapy begun.

RESULTS

In each patient, cyproheptadine produced rapid reversal of mydriasis within one hour of the initial dose. Other signs of serotonin syndrome remitted more slowly. As the signs and symptoms of serotonin syndrome remitted and pupils returned to normal size and reactiveness, cyproheptadine therapy seemed to produce mydriasis after each dose. Cessation of therapy after this point did not result in recurrence of symptoms. One patient developed serotonin syndrome twice. Two patients developed serotonin syndrome during treatment with medications that are partial serotonin antagonists (mirtazapine and nefazodone).

CONCLUSIONS

Rapid reversal of mydriasis in serotonin syndrome by cyproheptadine may serve as a specific suppressive test for the condition, and possibly may add to our understanding of the syndrome. Treatment with cyproheptadine is not thought to abbreviate the illness, but provides symptomatic relief while symptoms persist.

Serotonin Toxicity Associated with Concomitant Use of Linezolid

OBJECTIVE:

To report 2 cases of serotonin toxicity (ST) associated with concomitant use of linezolid and serotonergic drugs and review previously published case reports.

CASE SUMMARIES:

Case 1. A 38-year-old white female with cystic fibrosis treated with venlafaxine 300 mg/day for one year was prescribed linezolid 600 mg intravenously every 12 hours for treatment of methicillin-resistant Staphylococcus aureus (MRSA) pulmonary infection. She displayed symptoms of ST 8 days after the introduction of linezolid. The venlafaxine dosage was decreased to 150 mg/day, and symptoms gradually abated over 36 hours. Case 2. A 37-year-old male with multiple myeloma received citalopram 40 mg/day and trazodone 150 mg/day for anxiety-related disorders. Linezolid treatment with 600 mg orally twice daily was instituted for MRSA cellulitis. The following day, the patient developed anxiety, panic attacks, tremors, tachycardia, and hypertension that persisted throughout linezolid treatment. Symptoms finally waned 5 days after linezolid treatment was stopped.

DISCUSSION:

The symptoms observed in our patients were consistent with Sternbach's criteria for ST. A review of published case reports showed a short time to onset of symptoms following the introduction of linezolid, generally within 1–3 days. Also of note is the use of relatively high dosages of serotonergic drugs. Use of the Naranjo probability scale indicated a possible relationship between the use of linezolid and the occurrence of ST in both cases.

CONCLUSIONS:

Clinicians should pay special attention to patients treated with serotonergic drugs, especially those receiving dosages in the higher end of the normal range who are prescribed linezolid, and consider tapering or reducing the dosage of serotonergic drugs for the duration of antibiotic therapy.

Toxicities of opioid analgesics: respiratory depression, histamine release, hemodynamic changes, hypersensitivity, serotonin toxicity

Opioid-induced respiratory depression is potentially life-threatening and often regarded as the main hazard of opioid use. Main cause of death is cardiorespiratory arrest with hypoxia and hypercapnia. Respiratory depression is mediated by opioid μ receptors expressed on respiratory neurons in the CNS. Studies on the major sites in the brainstem mediating respiratory rate suppression, the pre-Bӧtzinger complex and parabrachial complex (including the Kӧlliker Fuse nucleus), have yielded conflicting findings and interpretations but recent investigations involving deletion of μ receptors from neurons have led to greater consensus. Some opioid analgesic drugs are histamine releasers. The range of clinical effects of released histamine include increased cardiac output due to an increase in heart rate, increased force of myocardial contraction, and a dilatatory effect on small blood vessels leading to flushing, decreased vascular resistance and hypotension. Resultant hemodynamic changes do not necessarily relate directly to the concentration of histamine in plasma due to a range of variables including functional differences between mast cells and histamine-induced anaphylactoid reactions may occur less often than commonly believed. Opioid-induced histamine release rarely if ever provokes bronchospasm and histamine released by opioids in normal doses does not lead to anaphylactoid reactions or result in IgE-mediated reactions in normal patients. Hypersensitivities to opioids, mainly some skin reactions and occasional type I hypersensitivities, chiefly anaphylaxis and urticaria, are uncommon. Hypersensitivities to morphine, codeine, heroin, methadone, meperidine, fentanyl, remifentanil, buprenorphine, tramadol, and dextromethorphan are summarized. In 2016, the FDA issued a Drug Safety Communication concerning the association of opioids with serotonin syndrome, a toxicity associated with raised intra-synaptic concentrations of serotonin in the CNS, inhibition of serotonin reuptake, and activation of 5-HT receptors. Opioids may provoke serotonin toxicity especially if administered in conjunction with other serotonergic medications. The increasing use of opioid analgesics and widespread prescribing of antidepressants and psychiatric medicines, indicates the likelihood of an increased incidence of serotonin toxicity in opioid-treated patients.

Possible Serotonin Syndrome in Association With 5-HT3 Antagonist Agents

The serotonin syndrome results when serotonergic activity increases to abnormally high levels. It occurs with selective serotonin reuptake inhibitors (SSRIs), opioids, and other serotonergic agents when the serotonin system has been modulated by another serotonergic agent or compromised by illness. Although the symptoms are quite variable, the syndrome is characterized by a triad of altered mental status, neuromuscular abnormalities, and autonomic dysfunction. The authors report the probable occurrence of the serotonin syndrome with serotonin receptor subtype 3 (5-HT(3)) antagonist therapy when used to control nausea associated with chemotherapy in two seriously ill children. The first case involves combined use with mirtazapine and the second with fentanyl. These agents may pose a potential risk when used in such combination in seriously ill patients.

Myelosuppression and serotonin syndrome associated with concurrent use of linezolid and selective serotonin reuptake inhibitors in bone marrow transplant recipients

We report 2 cases of serotonin syndrome and myelosuppression in bone marrow transplant recipients who received linezolid in combination with a selective serotonin reuptake inhibitor (SSRI). Given the risks to patients in this high-risk group, we recommend that this combination of medications be avoided if alternative antibiotic therapy is possible. If no alternative therapy is possible, prescribers should discontinue SSRI therapy and monitor these patients closely for evidence of serotonin syndrome or the development of hematological toxicity.

Serotonin syndrome caused by interaction between citalopram and fentanyl

OBJECTIVE

To report a case of serotonin syndrome associated with interaction between fentanyl and citalopram, as evidenced by medication history, clinical features and reversal following discontinuation of fentanyl.

CASE SUMMARY

A 65-year-old patient chronically treated with the selective serotonin reuptake inhibitor (SSRI) citalopram developed confusion, agitation, tachycardia, tremors, myoclonic jerks and unsteady gait, consistent with serotonin syndrome, following initiation of fentanyl, and all symptoms and signs resolved following discontinuation of fentanyl. Based on the Naranjo probability scale, serotonin syndrome was a probable adverse reaction associated with co-administration of citalopram and fentanyl.

DISCUSSION

Serotonin syndrome is a potentially lethal pharmacodynamic interaction between medications that increase serotonergic transmission at the synaptic junction. The development of new pharmacological agents with varied properties and actions has increased the risk of serotonin syndrome as a clinical diagnosis. SSRIs and fentanyl are commonly co-administered, especially in the setting of chronic or malignant pain, as underlying depression may contribute to the pathogenesis of pain.

CONCLUSION

Healthcare professionals should be aware of the possible development of serotonin syndrome as a complication of initiation of fentanyl and other phenylpiperidine opioids in patients treated with SSRIs.

Qualitative review of serotonin syndrome, ecstasy (MDMA) and the use of other serotonergic substances: hierarchy of risk

Growth of the antidepressant market and widespread use of the illicit drug ecstasy (methylenedioxymethamphetamine; MDMA) creates a need to delineate the potential harms associated with the concomitant use of ecstasy and serotonergic pharmaceutical drugs. One such harm is serotonin syndrome. The study aimed to synthesize the risk of serotonin syndrome associated with the concomitant use of ecstasy and other serotonergic substances in a clinically relevant hierarchy for psychiatrists and other medical practitioners. An extensive online database search was carried out of the literature on serotonin syndrome, in relation to illicit drugs and simultaneous use of other substances. Numerous licit and illicit substances implicated in serotonin syndrome, when used with ecstasy, have potential for increased toxicity and are presented in a resulting hierarchy of risk. Substances that inhibit serotonin re-uptake are less likely to lead to life-threatening elevations in serotonin when used with ecstasy. High doses or repeated use of stimulants such as methamphetamine and cocaine with ecstasy increase the risk of serotonin syndrome; as does the use of pharmaceutical amphetamine and ecstasy. Serotonin precursors also influence the course of serotonin syndrome when used with ecstasy. Substances that inhibit monoamine oxidase are most likely to lead to serious increases in serotonin when used with ecstasy. Findings highlight the importance of screening for the use of ecstasy and other serotonergic substances when prescribing antidepressant drugs.