Serum Concentration of Paliperidone Palmitate Administered Every 3 Weeks.

Schizophrenia, a disabling yet relatively common mental illness, is often controlled by antipsychotic drugs. However, long-term treatments are subject to non-adherence and consequent treatment failure. Non-adherence can be reduced by administration of slow-release drugs such as intramuscularly injected (IM) paliperidone palmitate. Considerable inter- and intra-individual variation in serum drug concentration exists, whose effect on clinical efficacy remains unclear. We report two cases of off-label use resulting in serum paliperidone levels greatly exceeding the recommended therapeutic window. A 20- and 31-year-old male were treated with 150 mg IM paliperidone palmitate/21 days. After one and two years, blood drug concentrations were 240 nmol/l and 610 nmol/l, respectively. Neither patient exhibited major adverse effects. Thus paliperidone serum levels greatly in excess of recommended targets can be well tolerated, although we urge caution with off-label use of paliperidone palmitate as it is not always the most appropriate way to achieve the control of schizophrenia.

Induction of Psychosis by Cyclobenzaprine.

Due to the stringent regulatory environment for therapeutics, common side-effects of drugs in the general population are largely well-documented. This is however less the case with certain patient subgroups who may exhibit significant adverse responses to therapeutics that are otherwise well-tolerated. We report a case of psychosis induced by exposure to a commonly prescribed drug to treat muscle spasms and associated pain cyclobenzaprine (Flexeril®). Cyclobenzaprine is structurally very similar to tricyclic anti-depressants, such as amyltriptine. While it is well known that agitation caused by cyclobenzaprine is not an uncommon occurrence in the elderly, there have also been sporadic reports of significant psychosis in association with the use of cyclobenzaprine in younger patients. We report a case of reversible mania in a susceptible 44-year-old patient with a lengthy history of mild borderline personality and bipolar disorder. Shortly after being treated with cyclobenzaprine for pain due to a minor injury, this patient exhibited significant signs of mania although these signs were readily reversible upon termination of the treatment with cyclobenzaprine. The patient's severe adverse reaction to this normally innocuous drug adds weight to the notion that there is reason for caution with its prescription for potentially susceptible patient subgroups.