Serotonin syndrome is a rare but serious condition that occurs when there is an excessive build-up of serotonin in the brain. While the risk of serotonin syndrome from ADHD medication alone is low, it increases when ADHD medication is combined with other medications, supplements, or substances that affect serotonin levels. 

Certain drugs and substances can elevate serotonin levels, either alone or in combination with ADHD medication. These include: 

• Selective serotonin reuptake inhibitors (SSRIs): Citalopram, Escitalopram, Fluoxetine, Fluvoxamine, Paroxetine, Sertraline 

• Serotonin and norepinephrine reuptake inhibitors (SNRIs): Duloxetine, Venlafaxine 

• Monoamine oxidase inhibitors (MAOIs): Isocarboxazid, Phenelzine, Tranylcypromine, Selegiline 

• Anxiety treatments: Buspirone 

• Migraine treatments: Almotriptan, Eletriptan, Frovatriptan, Sumatriptan, Zolmitriptan 

• Antibiotics: Linezolid 

• Pain medications: Fentanyl, Tramadol, Oxycodone, Methadone 

• Cough suppressants: Dextromethorphan 

• Nausea medications: Metoclopramide, Ondansetron 

• Mood stabilisers: Lithium 

• Recreational drugs and cannabis 

Symptoms typically appear within hours of taking a new medication or increasing the dose of an existing one. Common symptoms include: 

• Confusion 

• Restlessness or agitation 

• Dilated pupils 

• Headache 

• Nausea, vomiting, or diarrhoea 

• Rapid heart rate 

• Muscle twitching or tremors 

• Sweating or shivering 

• Stiff muscles 

• High fever 

• Seizures 

• Irregular heartbeat 

• Loss of consciousness 

• 30% of cases: Symptoms appear within 1 hour. 

• 60% of cases: Symptoms develop within 6 hours. 

With prompt treatment, serotonin syndrome typically resolves within 24 to 72 hours. However, if left untreated, it can be life-threatening, particularly if caused by multiple medications. 

If you experience mild symptoms, contact your healthcare provider immediately for advice. For severe symptoms like high fever, seizures, or loss of consciousness, call 999 or go to A&E without delay. 

For more information, visit the Serotonin Syndrome page on Patient.info, or discuss your concerns with your clinician during your next appointment.