The 'dalhousie serotonin cocktail' for treatment-resistant major depressive disorder

Therapeutic options for treatment-resistant depression

Treatment-resistant depression (TRD) presents major challenges for both patients and clinicians. There is no universally accepted definition of TRD, but results from the US National Institute of Mental Health's (NIMH) STAR*D (Sequenced Treatment Alternatives to Relieve Depression) programme indicate that after the failure of two treatment trials, the chances of remission decrease significantly. Several pharmacological and nonpharmacological treatments for TRD may be considered when optimized (adequate dose and duration) therapy has not produced a successful outcome and a patient is classified as resistant to treatment. Nonpharmacological strategies include psychotherapy (often in conjunction with pharmacotherapy), electroconvulsive therapy and vagus nerve stimulation. The US FDA recently approved vagus nerve stimulation as adjunctive therapy (after four prior treatment failures); however, its benefits are seen only after prolonged (up to 1 year) use. Other nonpharmacological options, such as repetitive transcranial stimulation, deep brain stimulation or psychosurgery, remain experimental and are not widely available. Pharmacological treatments of TRD can be grouped in two main categories: 'switching' or 'combining'. In the first, treatment is switched within and between classes of compounds. The benefits of switching include avoidance of polypharmacy, a narrower range of treatment-emergent adverse events and lower costs. An inherent disadvantage of any switching strategy is that partial treatment responses resulting from the initial treatment might be lost by its discontinuation in favour of another medication trial. Monotherapy switches have also been shown to have limited effectiveness in achieving remission. The advantage of combination strategies is the potential to build upon achieved improvements; they are generally recommended if partial response was achieved with the current treatment trial. Various non-antidepressant augmenting agents, such as lithium and thyroid hormones, are well studied, although not commonly used. There is also evidence of efficacy and increasing use of atypical antipsychotics in combination with antidepressants, for example, olanzapine in combination with fluoxetine (OFC) or augmentation with aripiprazole. The disadvantages of a combination strategy include multiple medications, a broader range of treatment-emergent adverse events and higher costs. Several experimental pharmaceutical treatment alternatives for TRD are also being explored in combination with antidepressants or as monotherapy. These less studied alternative compounds include pindolol, inositol, CNS stimulants, hormones, herbal supplements, omega-3 fatty acids, S-adenosyl-L-methionine, folic acid, lamotrigine, modafinil, riluzole and topiramate. In summary, despite an increasing variety of choices for the treatment of TRD, this condition remains universally undefined and represents an area of unmet medical need. There are few known approved pharmacological agents for TRD (aripiprazole and OFC) and overall outcomes remain poor. This might be an indication that depression itself is a heterogeneous condition with a great diversity of pathologies, highlighting the need for careful evaluation of individuals with depressive symptoms who are unresponsive to treatment. Clearly, more research is needed to provide clinicians with better guidance in making those treatment decisions--especially in light of accumulating evidence that the longer patients are unsuccessfully treated, the worse their long-term prognosis tends to be.

Once-daily high-dose pindolol for SSRI-refractory depression

Selective serotonin reuptake inhibitor (SSRI) augmentation with the 5-HT1A antagonist pindolol has met with mixed results. Recent studies using positron emission tomography (PET) suggest that pindolol doses used in these studies were too low to effect 5-HT1A autoreceptor blockade. To test the hypothesis that a single higher dose of pindolol would effectively augment antidepressant responses in SSRI-refractory patients, nine subjects with major depression unresponsive to paroxetine 40 mg/day given for 2 months or more were randomized to AM pindolol 7.5 mg (n=4) or placebo (n=5). Subjects were administered the Hamilton Depression Scale (HAM-D), the Hamilton Anxiety Scale (HAM-A), the Bech-Rafaelsen Melancholia Scale, and the Zung Depression Inventory at baseline and weeks 1, 2, 3, and 4. Subjects receiving pindolol exhibited significant improvements in all ratings beginning at week 2 which continued through week 4. Aside from transient dizziness and a five-point decrease in systolic/diastolic blood pressure associated with pindolol, no adverse effects were reported. Although results must be verified in a larger sample, these findings support previous studies indicating that pindolol can accelerate antidepressant responses during SSRI therapy. In addition, results reported here suggest that a single high dose of pindolol (7.5 mg) is a more effective augmentation strategy in SSRI-refractory patients compared with the same total dose given at 2.5 mg tid.