Antipsychotic drugs with SSRIs

Extrapyramidal side effects (EPS) associated with SSRI medications used as single agents were reported as early as 1979 (Meltzer et ah, 1979). Since then, several case reports have been published on use of fluoxetine (Elamilton and Opler, 1992), paroxetine (Nicholson, 1992), and sertraline (Opler 1994). The SSRI medications in combination with neuroleptics can cause severe EPS (Tate, 1989 Ketai, 1993) above and beyond what may be associated with increased levels of antipsychotic medications (Goff et ah, 1991), and are perhaps related to pharmacokinetic drug interactions. 

SSRIs are often prescribed with antipsychotic drugs, and some SSRIs inhibit CYP2D6, which can lead to increased blood concentrations of the antipsychotic drug. In 13 patients aged 26-56 years with schizophrenia, stabilized on risperidone 4-6 mg/day who took sertraline 50 mg/day for 4 weeks, plasma concentrations of risperidone and its major metabolite, 9-OH-risperidone, did not change... 

Acute dystonia is a recognized complication of treatment with antipsychotic drugs and it can also occur with SSRIs and the anxiolytic drug buspirone. 

Occasionally, long-term use of lithium is associated with cogwheel rigidity and a parkinsonian tremor (189). More often than not, concurrent or past treatment with an antipsychotic drug is involved. In a review of SSRI-induced extrapyramidal adverse effects, lithium was listed, but not discussed, as a possible risk factor (190). A review of drug-induced parkinsonism provided references to case reports of lithium s occasionally inducing or exacerbating parkinsonism (191). 

The adverse effects of lithium in elderly patients include cognitive status worsening, tremor, and hypothyroidism. The authors suggested that divalproex is also useful in elderly patients with mania and that concentrations of divalproex in the elderly are similar to those useful for the treatment of mania in younger patients. They noted that carbamazepine should be considered a second-line treatment for mania in the elderly. A partial response would warrant the addition of an atypical antipsychotic drug. For bipolar depression, they recommended lithium in combination with an antidepressant, such as an SSRI. They also noted that lamotrigine may be useful for bipolar depression. Electroconvulsive therapy (ECT) may also be useful, but there have been no comparisons of ECT and pharmacotherapy in elderly patients with bipolar depression. 

Drug interactions with lithium have been reviewed (569-573) another review focused on interactions in the elderly (573). A review of drug interactions with lithium considered both pharmacokinetic interactions [for example diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs)] and pharmacodynamic interactions (for example antipsychotic drugs, SSRIs) and summarized the most important ones in tabular form (569). 

Consistent with the role of both serotonin and dopamine in OCD, some OCD patients benefit from treatment with the new serotonin-dopamine antagonists (also known as atypical antipsychotics), especially when there is inadequate response to an SSRI. On the other hand, other patients have no therapeutic response to these new agents, and the condition of still others is even worsened by these drugs. The atypical antipsychotics and serotonin dopamine antagonism are discussed in Chapter 11. 

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