Focal necrotising vasculitis with secondary myositis following fluoxetine administration

Weight loss dynamics during combined fluoxetine and olanzapine treatment

Background

Fluoxetine and olanzapine combination therapy is rapidly becoming an effective strategy for managing symptoms of treatment-resistant depression. Determining drug-drug interactions, drug metabolism and pharmacokinetics is of particular interest for revealing potential liabilities associated with drug augmentation in special patient populations. In the current studies, we chronically administered fluoxetine and olanzapine in non-stressed rats to extend our previous findings regarding body weight dynamics.

Results

Chronic fluoxetine (10 mg/kg) and olanzapine (5 mg/kg and 0.5 mg/kg) treatment decreased weight gain irrespective of olanzapine dosing. At the 10 mg/kg and 5 mg/kg dose, respectively, fluoxetine and olanzapine also significantly reduced food and water consumption. This pharmacodynamic event-related effect, however, was not observed at the 10 mg/kg and 0.5 mg/kg dosing paradigm suggesting differences in tolerability rates as a function of olanzapine dose. The decrease in weight gain was not associated with apparent changes in glucose metabolism as vehicle- and drug-treated rats showed undistinguishable serum glucose levels. The combination of fluoxetine and olanzapine in rats yielded drug plasma concentrations that fell within an expected therapeutic range for these drugs in psychiatric patients.

Conclusions

These data suggest that fluoxetine and olanzapine treatment decreases weight gain in rats; a pharmacodynamic event-related effect that differs considerably from what is observed in the clinical condition. The possibility of mismatched models regarding body weight changes during drug augmentation therapy should be seriously considered.

Chronic fluoxetine differentially affects 5-hydroxytryptamine (2A) receptor signaling in frontal cortex, oxytocin- and corticotropin-releasing factor-containing neurons in rat paraventricular nucleus

Differential adaptive changes in serotonin2A [5-hydroxytryptamine (5-HT)2A] receptor signaling during treatment may be one mechanism involved in the latency of therapeutic improvement with antidepressants, such as fluoxetine. We examined the effects of fluoxetine (2, 3, 7, 21, or 42 days) on hypothalamic 5-HT2A receptor signaling. The hormone responses to an injection of the 5-HT2A receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-amino-propane HCl (DOI) were used as an index of hypothalamic 5-HT2A receptor function. Treatment with fluoxetine for 21 or 42 days produced diminished adrenocorticotropic hormone (ACTH) and oxytocin (but not corticosterone) responses to DOI injections (2.5 mg/kg i.p.; 15 min postinjection). Regulators of G protein signaling 4 and Galphaq protein levels in the hypothalamic paraventricular nucleus were not altered during fluoxetine treatment. Because previous studies indicate that treatment with fluoxetine for 21 days resulted in increased hormone responses to DOI when measured at 30 min after injection, we examined the effect of fluoxetine (21 days) on DOI-induced increase hormone levels at 15, 30, and 60 min after DOI injection. Fluoxetine decreased the oxytocin response at 15 but not at 30 min post-DOI injection, and potentiated the ACTH and corticosterone responses at 30 min post-DOI injection. For comparison, we examined the effect of fluoxetine on 5-HT2A receptor-mediated increase in phospholipase C (PLC) activity in the frontal cortex. 5-HT-stimulated, but not guanosine 5'-O-(3-thio)triphosphate-stimulated PLC activity was increased after 21 days of fluoxetine-treatment. Overall, these results indicate that chronic fluoxetine treatment can potentiate 5-HT2A receptor signaling in frontal cortex but differentially alters 5-HT2A receptor signaling in oxytocin-containing neurons and corticotropin-releasing factor-containing neurons in the paraventricular nucleus.

Drug-induced vasculitis

DIV is a relatively common cause of inflammatory vasculitis. Drugs from almost every pharmacologic class have been implicated in causing vasculitis in sporadic cases. The level of certainty and quality of evidence for these associations between specific agents and vasculitis vary greatly. The clinical manifestations of DIV range from single organ involvement (most commonly, skin) to life-threatening multiorgan disease. The recently described subset of cases of DIV associated with positive tests for ANCA are an interesting subset of DIV. The diagnosis of DIV is usually one of exclusion. The treatment of DIV is dependent on the severity of disease activity but should always include withdrawal of the suspected drug. If no agent can be implicated, as many drugs as feasible should be discontinued. The necessity of prescribing glucocorticoids or immunosuppressive agents depends on the disease severity and other case-specific information. Increasing understanding of the pathophysiologic characteristics of all inflammatory vasculitides should lead to better diagnostic and therapeutic approaches to DIV.