Further evaluation for possible causes of Ms. Y’s symptoms include a chest radiography and blood and urine cultures, which are unremarkable. Results of a lumbar puncture are within normal limits. Computed tomography of the head reveals confluent periventricular hypodensities compatible with moderate to severe non-specific white matter disease.
Carnitine: Supplementation usually isn’t necessary
Carnitine is derived from an amino acid and found in nearly all cells of the body. “Carnitine” is used to refer to several compounds, including L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine. The natural form and the only one with biologic activity is the geometric isomer L-carnitine. Most endogenous L-carnitine is derived from diet— meat and dairy are the primary sources—and the remainder is synthesized.2-4
Carnitine transports long-chain fatty acids into the mitochondria so they can be oxidized to produce energy and transports toxic compounds out of the mitochondria to prevent them from accumulating. Carnitine is concentrated in tissues that use fatty acids as a dietary fuel, such as skeletal and cardiac muscle.2-4 The body makes enough carnitine to meet most person’s needs and supplementation typically is not required. Some drugs, such as valproic acid and carbamazepine, can reduce carnitine blood concentrations.2
Because of its role in fatty acid oxidation, carnitine often is promoted as a weight loss aid. In addition, it is purported to improve exercise performance and enhance well-being.3,4 However, there is no consistent evidence that carnitine supplements can improve physical performance in healthy individuals.5
At doses of approximately 3 g/d, carnitine supplements can cause nausea, vomiting, abdominal cramps, diarrhea, and a “fishy” body odor. Rare side effects include muscle weakness in uremic patients and seizures in those with a seizure disorder.2-4
In animal studies, carnitine persistently increases dopamine outflow in the nucleus accumbens.6 Dopamine dysregulation in this pathway has been shown to cause psychotic symptoms.7
TREATMENT: Rapid improvement
Ms. Y’s renal dysfunction resolves within 24 hours with aggressive hydration and supportive therapy. Her WBC count normalizes and her CPK decreases.
When Ms. Y becomes more cooperative, the CL team pieces together more of her story with further interviews and collateral information from her cousin. Ms. Y’s family history includes an aunt with schizophrenia. Three years ago Ms. Y moved from the Midwest to a large Southern city with her husband, from whom she is divorced. She has 2 children who were removed from her custody when she was a teenager for unclear reasons. At admission, she lives with her boyfriend, whom she plans on marrying.
Ms. Y says she was taking carnitine to improve her energy and lose weight. She recalls that her physicians advised her to discontinue carnitine supplements, but she continued to take “4 or 5 a day” in an ongoing attempt to lose weight. When asked about other supplements, Ms. Y reports regularly consuming 16-ounce energy drinks, including the day before admission. The label on this drink lists L-carnitine and caffeine as main ingredients. She denies regularly drinking other caffeine-containing beverages, including coffee, tea, or soda.
The authors’ observations
Supplements for weight loss may appeal to people’s desire for a “quick fix” that is less demanding than diets and increased physical activity. Supplements are available without a prescription and despite reports of adverse reactions generally are perceived as being safe and having few side effects. These supplements may be marketed as “natural,” which can be misinterpreted as an assurance of safety and efficacy.
Given the similarities of the current admission to the one 6 months ago, we suspect Ms. Y is experiencing transient psychosis secondary to carnitine intoxication. Based on Ms. Y’s boyfriend’s report and the product labeling, we estimate that Ms. Y took approximately 4,000 mg of carnitine in the 24 hours before admission.
Other causes of transient psychosis, such as infectious, metabolic, and neoplastic processes, were considered and ruled out. Seizures with postictal confusion also was ruled out because Ms. Y does not have a history of seizures and there is no evidence of convulsive activity, incontinence, or buccal lacerations. Given Ms. Y’s family history of schizophrenia and reported history of psychotic symptoms as a teenager we considered that she may have an endogenous psychotic disorder. However, her psychotic symptoms were transient, and Ms. Y returned to her baseline level of functioning between episodes.
OUTCOME: Advice to stop
We start Ms. Y on risperidone, 2 mg/d, at bedtime for her psychotic symptoms. Her psychotic symptoms quickly improve. She seems to return to her baseline state approximately 36 hours after admission and is medically cleared for discharge. Risperidone is discontinued after only 1 dose.