A large number of medications and street drugs can cause<unk>  when taken alone at high doses or in combination with other serotonergic drugs. The table below lists some of these drugs. Class Drugs that can induce<unk>  Antidepressants Monoamine oxidase inhibitors (MAOIs), TCAs,<unk> RIs, SNRIs, nefazodone, trazodone Opioids Dextropropoxyphene, tramadol, tapentadol, pethidine (meperidine), fentanyl, pentazocine, buprenorphine oxycodone, hydrocodone CNS stimulants MDMA, MDA, methamphetamine, lisdexamfetamine, amphetamine, phentermine, amfepramone (diethylpropion),<unk>  releasing agents like hallucinogenic substituted amphetamines, sibutramine, methylphenidate, cocaine 5-HT1 agonists Triptans Psychedelics 5-Methoxy-diisopropyltryptamine, alpha-methyltryptamine, LSD Herbs St John's Wort, Syrian rue, Panax ginseng, Nutmeg, Yohimbe Others Tryptophan, L-Dopa, valproate, buspirone, lithium, linezolid, dextromethorphan, 5-hydroxytryptophan, chlorpheniramine, risperidone, olanzapine, ondansetron, granisetron, metoclopramide, ritonavir, metaxalone Many cases of<unk>  toxicity occur in people who have ingested drug combinations that synergistically increase synaptic<unk> . It may also occur due to an overdose of a single serotonergic agent. The combination of MAOIs with precursors such as L-tryptophan or 5-HTP pose a particularly acute risk of life-threatening<unk> . The case of combination of MAOIs with tryptamine agonists (commonly known as ayahuasca) can present similar dangers as their combination with precursors, but this phenomenon has been described in general terms as the "cheese effect". Many MAOIs irreversibly inhibit monoamine oxidase. It can take at least four weeks for this enzyme to be replaced by the body in the instance of irreversible inhibitors. With respect to tricyclic antidepressants only clomipramine and imipramine have a risk of causing<unk> . Many medications may have been incorrectly thought to cause<unk> . For example, some case reports have implicated atypical antipsychotics in<unk> , but it appears based on their pharmacology that they are unlikely to cause the<unk> . It has also been suggested that mirtazapine has no significant serotonergic effects, and is therefore not a dual action drug. Bupropion has also been suggested to cause<unk> , although as there is no evidence that it has any significant serotonergic activity, it is thought unlikely to produce the<unk> . In 2006 the United States Food and Drug Administration issued an alert suggesting that the combined use of<unk> RIs or SNRIs and triptan medications or sibutramine could potentially lead to severe cases of<unk> . This has been disputed by other researchers as none of the cases reported by the FDA met the Hunter criteria for<unk> . The condition has however occurred in surprising clinical situations, and because of phenotypic variations among individuals, it has been associated with unexpected drugs, including mirtazapine. The relative risk and severity of serotonergic side effects and<unk>  toxicity, with individual drugs and combinations, is complex.<unk>  has been reported in patients of all ages, including the elderly, children, and even newborn infants due to in utero exposure. The serotonergic toxicity of<unk> RIs increases with dose, but even in over-dose it is insufficient to cause fatalities from<unk>  in healthy adults. Elevations of central nervous system<unk>  will typically only reach potentially fatal levels when drugs with different mechanisms of action are mixed together. Various drugs, other than<unk> RIs, also have clinically significant potency as<unk>  reuptake inhibitors, (e.g. tramadol, amphetamine, and MDMA) and are associated with severe cases of the<unk> . Although the most significant health risk associated with opioid overdoses is respiratory depression, it is still possible for an individual to develop<unk>  from certain opioids without the loss of consciousness. However, most cases of opioid-related<unk>  involve the concurrent use of a serotergenic drug such as antidepressants. Nonetheless, it is not uncommon for individuals taking opioids to also be taking antidepressants due to the comorbidity of pain and depression. Cases where opioids alone are the cause of<unk>  are typically seen with tramadol, because of its dual mechanism as a<unk> -norepinephrine reuptake inhibitor.<unk>  caused by tramadol can be particularly problematic if an individual taking the drug is unaware of the risks associated with it and attempts to self-medicate symptoms such as headache, agitation, and tremors with more opioids, further exacerbating the condition.
Serotonin syndrome
Malignant hyperthermia
Cannabinoid hyperemesis syndrome
Neuroleptic malignant syndrome
Post-acute-withdrawal syndrome
Methanol toxicity
Glycine encephalopathy
Anticonvulsant hypersensitivity syndrome