Formication Caused by a Drug-Induced State of Psychosis

The father of a 28-year-old man accompanied his son to the emergency department (ED) for evaluation of a “worm infestation.” About 6 weeks earlier, the patient had diarrhea for 2 days and claimed to have seen worms in his stool. He went to an urgent care clinic, but it was unclear as to whether he received a diagnosis or prescription. The patient self-treated with pyrantel, which he said resolved the problem. Recently, the patient had exhibited bizarre behavior. He repeatedly told his father that the worms had returned and that he had specimens of them. When he presented to the ED, the patient had a large, open wound on his neck that may have been a few days old. He was cooperative and did not complain of pain. He said that his neck had become irritated because of a worm infestation and that he had used a pair of household scissors to cut out the worms. The patient underwent a toxicology screening. The test results were positive for cocaine, opiates, and benzodiazepines. On further questioning, the father described an ongoing change in his son’s behavior over the previous 6 months. During this time, the patient had been charged with driving while intoxicated and possession of a large amount of narcotics without a prescription. Tina Clark, CRNP, of Bel Air, Md, writes that formication is a type of paresthesia in which there is a sensation of ants crawling on the skin. This patient had a similar paresthesia, in which he had the sensation that worms were moving under his skin. This tactile hallucination was caused by a drug-induced state of psychosis. Although the patient was afebrile, he was given intravenous antibiotics. The ED physician recommended an emergency psychiatric evaluation. The patient was subsequently lost to follow-up after inpatient psychiatric treatment.