Case-Based Review

Calcineurin inhibitor–induced psychosis

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Mrs. C, age 68, is experiencing worsening paranoid delusions. She believes that because she lied about her income when she was younger, the FBI is tracking her and wants to poison her food and spray dangerous fumes in her house. Her paranoia has made it hard for her to sleep, eat, or feel safe in her home.

Mrs. C’s daughter reports that her mother’s delusions started 3 years ago and have worsened in recent months. Mrs. C has no psychiatric history. Her medical history is signifi­cant for renal transplant in 2015, type 2 diabetes, hyperlipidemia, hypertension, and hypothyroidism. She is currently normotensive. Mrs. C’s home medications include cyclosporine, which is a calcineurin inhibitor, 125 mg twice daily (trough level = 138 mcg/L); mycophenolate mofetil, 500 mg twice daily; cinacalcet, 30 mg 3 times a week; metformin, 500 mg twice daily; amlodipine, 5 mg twice daily; levothyroxine, 112 mcg/d; and atorva­statin, 40 mg at bedtime.

As you review her medications, you wonder if the cyclosporine she began receiving after her kidney transplant could be causing or contributing to her worsening paranoid delusions.

Kidney transplantation has become an ideal treatment for patients with end-stage renal disease. In 2020, 22,817 kidney transplants were performed in the United States.1 Compared with dialysis, kidney transplant allows patients the chance to return to a satisfactory quality of life.2 However, to ensure a successful and long-lasting transplant, patients must be started and maintained on lifelong immunosuppressant agents that have potential adverse effects, including nephrotoxicity and hypertension. Further, immunosuppressant agents—particularly calcineurin inhibitors—are associated with potential adverse effects on mental health. The most commonly documented mental health-related adverse effects include insomnia, anxiety, depression, and confusion.3 In this article, we discuss the risk of severe psychosis associated with the use of calcineurin inhibitors.

Calcineurin inhibitors and psychiatric symptoms

Cyclosporine and tacrolimus are calcineurin inhibitors that are commonly used as immunosuppressant agents after kidney transplantation. They primarily work by specifically and competitively binding to and inhibiting the calcineurin protein to reduce the transcriptional activation of cytokine genes for interleukin-2, tumor necrosis factor-alpha, interleukin-3, interleukin-4, CD40L (CD40 ligand), granulocyte-macrophage colony-stimulating factor, and interferon-gamma.4,5 The ultimate downstream effect is reduced proliferation of T lymphocytes and thereby an immunosuppressed state that will protect against organ rejection. However, this is not the only downstream effect that can occur from inhibiting calcineurin. Cyclosporine and tacrolimus may modulate the activity of dopamine and N-methyl-D-aspartate (NMDA) via calcineurin.6-8

An increased effect of dopamine in the mesocortical dopaminergic pathway has long been a suspected cause for psychotic symptoms. A study conducted in rodents suggested that tacrolimus selectively modifies the responsivity and sensitivity of postsynaptic dopamine-2 (D2) and dopamine-3 (D3) receptors.9 These receptors are important when discussing psychosis because antipsychotic medications work primarily by blocking dopamine D2, while many also block the D3 receptor. We hypothesize that modifying the responsivity and sensitivity of these 2 receptors could increase the risk of a person developing psychosis. It may also provide insight into how to best treat a psychotic episode.

Tacrolimus has been shown to elicit inhibition of NMDA-induced neurotransmitter release and augmentation of depolarization-induced neurotransmitter release.10 In theory, this potential inhibition at the NMDA receptors may lead to a compensatory and excessive release of glutamate. Elevated glutamate levels in the brain could lead to psychiatric symptoms, including psychosis. This is supported by the psychosis caused by many NMDA receptor antagonists, such as phencyclidine (PCP) and ketamine. Furthermore, a study examining calcineurin in knockout mice showed that the spectrum of behavioral abnormalities was strikingly similar to those in schizophrenia models.11 These mice displayed impaired working memory, impaired attentional function, social withdrawal, and psychomotor agitation. This further supports the idea that calcineurin inhibition can play a significant role in causing psychiatric symptoms by affecting both dopamine and NMDA receptors.

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