Antidepressant Overdose

What to do right now

1. Call 911 or your local emergency number if the person is drowsy, confused, having a seizure, has an abnormal heartbeat, or took the medicine on purpose.
2. Call Poison Control (1-800-222-1222 in the US) for any accidental extra dose, even without symptoms. Have the medicine bottle ready.
3. Do not make them vomit.
4. If they are unconscious but breathing, place them on their side in the recovery position.
5. If they stop breathing, start CPR if you are trained.
6. Bring the medicine packaging and any other pills to hospital, and note the time they were taken.
7. Stay with them. Remove access to other medicines.

Symptoms can be delayed for several hours, especially with extended-release tablets, so a person who looks fine still needs assessment.

Why the type of antidepressant matters

Tricyclic antidepressant overdose

Tricyclic overdose can become life-threatening within 1 to 6 hours. Signs include:

• drowsiness progressing to coma
• dilated pupils, dry hot skin, flushing, urinary retention (anticholinergic effects)
• fast heartbeat, low blood pressure and dangerous rhythms
• seizures
• breathing problems

Even a small number of tablets can be dangerous to a toddler.

Serotonin syndrome

Serotonin syndrome results from too much serotonin activity, after an overdose or when serotonin drugs are combined (for example an SSRI with tramadol, triptans, linezolid, MDMA, St John's wort or an MAO inhibitor). It develops within hours:

• mild: shivering, sweating, diarrhea, restlessness, tremor
• moderate: muscle twitching and jerking (clonus), especially in the legs, overactive reflexes, agitation, fever
• severe: temperature above 40 °C (104 °F), rigid muscles, seizures, confusion, collapse

Hospital treatment

• Assessment: vital signs, an ECG (the QRS width predicts seizures and heart rhythm problems in TCA overdose), blood tests including acetaminophen (paracetamol) and alcohol levels, because mixed overdoses are common. See drug overdose.
• Activated charcoal: may be given within about 1 to 2 hours if the person is awake and can protect their airway.
• Sodium bicarbonate: given intravenously for TCA overdose with a widened QRS, low blood pressure or abnormal rhythms.
• Seizures: treated with benzodiazepines.
• Serotonin syndrome: stopping all serotonin drugs, benzodiazepines for agitation, cooling, IV fluids and sometimes cyproheptadine; severe cases need intensive care.
• Breathing support and intensive care for coma, severe heart effects or high fever.
• Observation: usually at least 6 hours after a TCA or significant overdose, longer for extended-release products.

Mental health care after an overdose

After a deliberate overdose, people are assessed by a mental health professional before leaving hospital. Safety planning, follow-up and treatment of depression reduce the risk of repeat attempts. Treatment of underlying depression and suicidal thoughts continues after discharge. Practical measures help:

• prescribing smaller quantities at a time during high-risk periods
• choosing safer antidepressants for people at risk
• having family keep and dispense medicines
• removing stockpiled tablets from the home

Prevention of accidental overdose

• Use a weekly pill organizer and keep a medication list.
• Do not take an extra dose to make up for a missed one unless your pharmacist says to.
• Tell every prescriber and pharmacist about all medicines and supplements, including St John's wort and tramadol.
• Store medicines locked and out of children's sight.
• Dispose of unused medicines through take-back programs.

Frequently asked questions

What happens if you overdose on antidepressants?

It depends on the drug and amount. SSRIs alone usually cause drowsiness, vomiting, tremor and a fast heartbeat. Tricyclics can cause seizures, coma and dangerous heart rhythms within hours. Any overdose can trigger serotonin syndrome. All suspected overdoses need medical assessment.

Which antidepressant is most dangerous in overdose?

Tricyclic antidepressants such as amitriptyline, imipramine and doxepin are the most dangerous, causing most deaths from antidepressant overdose. Venlafaxine, bupropion and MAO inhibitors are also more toxic than SSRIs. Citalopram and escitalopram can affect heart rhythm at high doses.

What should I do if I accidentally took two antidepressant pills?

Call Poison Control (1-800-222-1222 in the US) or your pharmacist. A single extra SSRI dose is usually not dangerous for an adult, but advice depends on the drug, dose and your health. A double dose of a tricyclic or any dose taken by a child needs urgent advice.

What are the signs of serotonin syndrome?

Signs include agitation, shivering, sweating, diarrhea, a fast heartbeat, muscle twitching or jerking, overactive reflexes and fever. Severe cases cause very high temperature, rigid muscles, seizures and confusion. It usually starts within hours of an overdose or a new drug combination.

How long do overdose symptoms take to appear?

Symptoms often begin within 1 to 6 hours. With extended-release forms of venlafaxine or bupropion, effects such as seizures can be delayed up to 24 hours. That is why people are monitored in hospital even if they seem well at first.