Эффективность использования высоких доз антидепрессантов

Higher doses than those currently used might be modestly more effective, but come with higher risks of adverse effects.

Before writing medications off as ineffective or only partially effective, clinicians strive to optimize dosing. To better identify optimal doses for six selective serotonin reuptake inhibitors (SSRIs), investigators applied meta-analytic techniques to 40 studies involving 10,039 patients with major depression in placebo-controlled randomized trials who were treated with fluoxetine, (N=2386), fluvoxamine (N=910), paroxetine (N=3424), sertraline (N=865), citalopram (N=1349), or escitalopram (N=1105).

Focusing on efficacy and tolerability, investigators calculated number needed to treat (NNT) and number needed to harm (NNH). They used published dose ranges to convert SSRI doses to imipramine equivalents, with 100 mg of imipramine equivalent to:

Sertraline, 120 mg

Fluvoxamine, 100 mg

Paroxetine, 20 mg

Fluoxetine, 20 mg

Citalopram, 33.3 mg

Escitalopram, 16.7 mg

Statistical modelling adjusted for lag times of medication-effect onsets and for doses used in the trials (100–400 mg of imipramine equivalents). In dose-by-time interaction analyses, higher doses yielded greater therapeutic responses. Greatest efficacy was seen for 200–250-mg imipramine equivalents, compared with higher and lower ranges (NNTs: compared with placebo, 3; in lower-dose comparisons, 14–16). Compared with low doses, higher dose was associated with greater likelihood of dropout due to adverse effects (NNHs, 45–48), but all-cause dropouts were fewer at higher doses, presumably due to efficacy. Fluvoxamine, approved for depression in other countries but not by the FDA, was excluded in some analyses, which yielded similar overall results.

Comment

These findings generally support the use of higher dose ranges for several SSRIs for major depression that did not respond or only partially responded to SSRIs. Most clinicians treating obsessive-compulsive disorder and bulimia nervosa are already comfortably using these higher doses. However, distinctions among SSRIs are warranted; for example, the FDA has issued warnings about QTc interval prolongation with higher doses of citalopram.

 Optimal Doses for SSRIs in Treating Depression: Meta-Analytic Results

Фармакогенетика СИОЗС, ассоциации между полиморфизмом CYP2D6 и CYP2C19 и ответом на терапию антидепрессантом

An investigation of MEDLINE and other database resources was carried out to summarize the research conducted between 1970 and 2003 in the role of CYP2D6 genetics on SSRI dose exposure.^[2] Area-under-the-concentration curve (AUC) values of 5 SSRIs in poor metabolizers, intermediate metabolizers, and extensive metabolizers as a measure of bioavailability were collected. Dose adjustments were then calculated to compensate for variability in CYP2D6 metabolizer status in white patients. On the basis of metabolizer phenotype, the following dose adjustments were extrapolated for extensive vs poor metabolizers: 33%-129% for fluvoxamine, 66%-114% for paroxetine, 56%-119% for fluoxetine (including the AUC of its active metabolite), 98%-101% for citalopram, and 99-100% for sertraline. A dose adjustment of 130% for paroxetine was extrapolated for ultrarapid metabolizers.

However, the study authors concluded that dose adjustments that are based on CYP2D6 could not be recommended for SSRIs for various reasons. They noted the limited data from multiple dosing, which more accurately reflects the clinical situation; the unknown effect of saturation kinetics of some SSRIs (eg, paroxetine and fluvoxamine); and the long-term effect of inhibition of CYP2D6 by some SSRIs (eg, fluoxetine, fluvoxamine, and paroxetine) when given in chronic treatment regimens. Thus, basic human pharmacokinetic data do not strongly support routine clinical use of CYP2D6 testing.

Another study scanning 1200 Web-based articles between 1966 and 2006 for treatment of major depression found no consistent association between CYP2D6 genotype and SSRI metabolism, efficacy, or risk for side effects.^[3]Although 2 studies showed greater nonresponse to SSRIs among ultrarapid metabolizers relative to the general population, the data were inconsistent across other studies. The study authors concluded that there is no established association between plasma drug concentration and SSRI drug response at standard doses.

Finally, a study of SSRI drug response and tolerability in 1953 patients enrolled in the Sequenced Treatment of Alternatives to Relieve Depression (STAR*D) study also showed no significant association between CYP2D6 variants and citalopram response, remission, or tolerability when comparing extensive metabolizers with poor metabolizers. However, the study design included numerous concomitant medications with unknown confounding effects.^[4]

The complexity derived from interaction between multiple CYP enzymes was highlighted in a study of the impact of extensive and poor metabolizer status for CYP2D6 and CYP2C19 on the SSRI citalopram. Researchers showed that the AUC for citalopram correlated with the combined CYP2D6/CYP2C19 metabolizer status.^[5] For example, individuals with CYP2D6 extensive metabolizer/CYP2C19 poor metabolizer status showed significantly higher citalopram AUC compared with extensive/extensive metabolizer or poor/extensive metabolizer carriers. Because citalopram metabolism is preferentially catalyzed by CYP2C19 over CYP2D6, consideration of more than 1 genetic variant may be necessary to guide medication dosing decisions.

Pharmacogenomics of SSRIs: Clinical Implications

Нейротоксичность лития при нормальных концентрациях

To the Editor: Lithium is used with great success in the treatment and prophylaxis of bipolar disorders, unipolar recurrent depression, and endogenous depression that is resistant to conventional treatment. It is also known to be neurotoxic at higher serum levels. In rare cases patients develop symptoms of intoxication even with normal lithium levels.

Case Report

A 61-year-old man with history of bipolar disorder that was managed with lithium for more than 20 years presented with complaints of psychomotor slowdown, unsteady gait, memory deficits, restlessness, sleep disorder, and severe tremor in his hand that prevented him from eating or drinking properly. These symptoms had begun in the previous week. There was no recent history of fever, respiratory, gastrointestinal, or urinary complaints. He was medicated with lithium, 800 mg/day, and fluvoxamine, 200 mg/day, and the dosage of his medication had remained unchanged over the last year.

Neurological examination showed psychomotor slowdown, inattention, temporal disorientation, severe episodic memory impairment, motor and verbal perseveration, slurred speech, and hypophonia. Symmetrical global and segmental bradykinesia and lead-pipe rigidity, as well as tremor at rest, intention, and posture, were also evident. His gait was abnormal with shuffling small steps and a hunched-forward upper body.

An analytic study revealed no abnormalities, including CBC, renal, thyroid and hepatic function, and PCR. Lithium serum levels were normal (1.0 mmol/liter).

EEG showed diffuse slow background activity, mainly at 5–6 Hz, with periods of greater lentification at 3 Hz, which is compatible with moderate to severe encephalopathy. A brain CT was normal. The patient was admitted and lithium was stopped. There was remarkable clinical improvement over the next days, and he was discharged at day 5, asymptomatic and on valproic acid (300 mg/day).

Lithium Neurotoxicity at Normal Serum Levels

Антидепрессанты и катаракта

Researchers found patients taking SSRIs were overall 15 percent more likely to be diagnosed with cataracts or to have cataract surgery.

The degree of risk among specific and different types of SSRIs varied considerably. Taking fluvoxamine (Luvox) led to a 51 percent higher chance of having cataract surgery, and venlafaxine (Effexor) carried a 34 percent higher risk.

No connection could be made between fluoxetine (Prozac), citalopram (Celexa), and sertraline (Zoloft) and having cataract surgery.

Some Antidepressants Related to Cataract Risk

Anxiety Disorders in Children and Adolescents. Early Identification and Evidence-Based Treatment

Anxiety Disorders in Children and Adolescents