Rare case of Serotonin syndrome due to therapeutic dose of Tramadol, bezoar underlying culprit

In the recent issue of Hindawi journal- Case reports in Psychiatry, Palimaru et al have reported a case where an autistic women having pica behaviour suffered from opioid overdose with normal dose of tramadol. The underlying culprit was subsequently found to be a gastric bezoar.

Pica can be encountered in several contexts of iron deficiency anemia, pregnancy, psychiatric conditions (e.g., depression, anxiety including trichotillomania, intellectual disability (ID), and autism spectrum disorder (ASD)). Bezoars can be asymptomatic, or they can cause nonspecific symptomatology such as nausea, vomiting, abdominal pain, and digestive bleeding.

A 38-year-old woman with nonverbal autism, epilepsy, and severe ID, was hospitalized in the neurobehavioural unit because of the installation of a severe pica behaviour for three years. It was found that the problematic behaviour was ingestion of inedible foreign objects and gastroduodenal fibroscopy showed a gastric bezoar with multiple plastic foreign bodies, especially straws, medical compresses, and gloves.

She was discharged on antiepileptics and anxiolytics. A few weeks later she presented with a deterioration of her general condition. She intensified a compulsive motor activity (repeatedly packing/unpacking her bedclothes), and she became painful on abdominal palpation; in addition, she had diarrhoea. In the hypothesis of a subocclusive syndrome due to her severe pica behaviour, a colonic lavage was done which allowed the elimination of a medical compress, and then, tramadol 225 mg/d was given to calm her pain. During this episode, the biological assessment showed an inflammatory syndrome, iron deficiency anemia, dearranged liver enzymes, rhabdomyolysis, and cardiac injury.

A day later patient developed heart rate of 150 bpm, systolic arterial pressure of 130mm/Hg, saturation-91% and peripheral temperature at 38.2 °C. The patient presented several desaturations with a Glasgow score of 3 in the evening. She was transferred to the ICU.

The main hypothesis raised was tramadol overdose because of the immediate response when opioid antagonist naloxone was administered. The outcome was favourable, the patient became fully vigilant a few hours after the administration of the antidote. She underwent an exploratory laparotomy two weeks later to completely remove the bezoar.

What was the underlying cause?

The constellation of symptoms suggested a possibility of a serotonin syndrome (agitation, restlessness, rhabdomyolysis, coma, tachycardia, hyperthermia, shivering, and diarrhoea). Tramadol overdose in combination with sertraline probably contributed to the apparition of a serotonin syndrome.

"Even if we did not exceed the recommended prescription dosage of tramadol, the presence of gastric bezoar is assumed to have slowed the absorption of the drug, and the consequence was an opioid overdose", noted the authors.

The treatment of anemia by iron supplementation and intensive behavioural therapy allowed for an improvement in her pica behaviour.

Clinical message: In patients for whom symptoms suggest a lack of dosage or drug plasma levels exceeding known or expected pharmacokinetics principles, the presence of a foreign mass like a bezoar inside the gastrointestinal tract should be considered. A bezoar could temporarily block the absorption of a drug followed by a subsequent overdose.

Source: Case Reports in Psychiatry: https://doi.org/10.1155/2021/7334467