Key points
- We recommend to consult your poison centre with the use of this antidote.
- Cyproheptadine is an adjunct to benzodiazepines (please refer to the benzodiazepines monograph).
- Cyproheptadine is a first generation antihistamine (H1 receptor antagonist) with non-specific serotonin (5-HT2) antagonist activity. It also has anticholinergic properties that should be considered prior to its use.
- The absorption of the cyproheptadine may be reduced if the patient has received activated charcoal. In such cases, consider using another serotonin antagonist, such a, olanzapine (SL, IM) or risperidone (SL, IM).
+ Synonyms and other terms
- Cyproheptadine HCl
- Cyproheptadine hydrochloride
- Periactin™
+ Indications
- Moderate to severe serotonin toxicity.
- If the patient has been exposed to one or a combination of serotonergic agents, which is indicated by the presence of either:
- Spontaneous clonus; or
- Inducible clonus plus agitation or diaphoresis; or
- Ocular clonus plus agitation or diaphoresis; or
- Tremors associated with hyperreflexia; or
- Hypertonia with body temperature above 38°C plus ocular or inducible clonus.
+ Dosage
+ Pediatric Dose
- 1 - 2 mg/dose PO or NG tube every 1 to 4 h until resolution of symptoms or a maximum of 12 mg/day.
+ Adult Dose
- 12 mg PO or NG tube, followed by 2 to 4 mg every 2 h until resolution of symptoms or a maximum of 32 mg/day
- If treatment is to be continued for more than 24 h, contact your poison centre.
+ Renal Impairment
No data suggests that the dose should be modified for short-term use.
+ Hepatic Impairment
No data suggests that the dose should be modified for short-term use.
+ Hemodialysis Patient
At the end of dialysis, administer 50 - 100% of the dose previously administered.
+ Pregnancy
- Possibly safe.
- Do not hesitate to use cyproheptadine during pregnancy if the anticipated toxic effects pose a significant risk of morbidity or mortality.
- Considerations other than pregnancy should help in selecting the antidote to be used.
- No data suggests that the dose should be modified for short-term use.
+ Obese or Overweight Patient
No data suggests that the dose should be modified for short-term use.
+ Adverse effects
- Anticholinergic effects such as urinary retention, drowsiness, confusion, tachycardia, xerostomia, mydriase etc.
+ Monitoring
- Vital signs
- Level of sedation
+ End of treatment
- Resolution of clinical signs of serotonin toxicity for 24 h.
+ Special Notes on Administration
Enteral route
- PO
- NG tube
- Syrup formulation is preferred form.
- If not available:
- Finely grind tablets with a pestle and mortar extemporaneously.
- Dissolve the resulting powder in 10 - 30 ml of sterile water for injection and draw up the resulting liquid using an oral syringe.
- Rinse NG tube with 15 - 30 ml of sterile water for injection before administration.
- Administer the antidote by NG tube.
- Quickly rinse NG tube with 15 - 30 ml of sterile water for injection.
+ Available products
- Cyproheptadine, 4 mg/tablet, Jamp Pharma , DIN 02332248,
- Euro - cyproheptadine, 4 mg/tablet, Euro - Pharm , DIN 02245667,
- Euro - cyproheptadine, 2 mg/5 ml, Oral Sol., Euro - Pharm , DIN 02245668,
- Pms - cyproheptadine, 4 mg/tablet, Pharmascience , DIN 00757713,
+ Amount required to treat a person weighting 70kg during 24 hours
- At least 32 mg.
+ References
Boyer, Edward W., and Michael Shannon. 2005. “The Serotonin Syndrome.” The New England Journal of Medicine 352 (11):1112–20.
Kapur et al, Cyproheptadine: A Potent In vivo Serotonin Antagonis, Letter to the Editor, Am J Psychiatry 153:6, June 1997
Simone, Karen E. 2016. “Cyproheptadine.” In Critical Care Toxicology, edited by Jeffrey Brent, Keith Burkhart, Paul Dargan, Benjamin Hatten, Bruno Megarbane, and Robert Palmer, 1–9. Springer International Publishing.
© Centre antipoison du Québec, CIUSSS de la Capitale-Nationale, 2017. The information contained in this site may be cited, provided the source is acknowledged. Any use for commercial or advertising purposes is strictly prohibited.
