Milnacipran: serotonin-noradrenaline reuptake inhibitor approved for fibromyalgia may be a useful antidepressant.

OBJECTIVE: Milnacipran is a serotonin noradrenaline reuptake inhibitor (SNRI) approved for treatment of fibromyalgia in Australia, but is used for depression in Europe and elsewhere. This paper will briefly review milnacipran and its utility in psychiatry for the treatment of depression. CONCLUSION: Milnacipran is a dual reuptake inhibitor of noradrenaline and serotonin, with greater effect on noradrenaline than serotonin, in contrast to the related drugs venlafaxine, desvenlafaxine and duloxetine. Rapidly absorbed irrespective of food, milnacipran has a half-life of approximately 8 hours, reaches steady state in 2 days and is excreted renally. Milnacipran helps a minority of patients with fibromyalgia by reducing pain and fatigue. It is also an effective antidepressant with efficacy comparable to venlafaxine and duloxetine, and a side effect profile characteristic of SNRIs. The dose range is 50-200 mg, in divided doses. Milnacipran may be useful for patients with depression and pain, and endogenous depression characterised by anergia, psychomotor retardation and hypersomnia. Caution is necessary in the presence of heart disease, hypertension, renal impairment, epilepsy, glaucoma, bipolar disorder, and bleeding tendency. Milnacipran is likely to be a useful late antidepressant option in treatment-resistant patients, as well as those with chronic pain, anergia and hypersomnia.

Suvorexant: scientifically interesting, utility uncertain.

OBJECTIVE: Suvorexant, a new hypnotic, is indicated for the treatment of insomnia characterized by difficulties with sleep onset and/or sleep maintenance, and is used long-term. This paper will briefly review suvorexant. RESULTS: Orexin is a hypothalamic peptide which promotes wakefulness. By blocking orexin receptors, suvorexant induces sleep. Peaking 2 h after ingestion, it has a half-life of 12 h and is hepatically metabolized mainly by CYP3A. Kinetics are not affected by age but concentrations are higher in females and obese patients. There may be interactions with benzodiazepines, antidepressants and antipsychotics. Suvorexant is available in 15 mg and 20 mg doses at which benefits are moderate: after three months' treatment users fell asleep 6 min faster and slept 16 min longer than those on placebo. Studies with 40 mg showed greater benefits but more side effects: next day somnolence, fatigue, xerostomia and peripheral oedema. Hallucinations, sleep paralysis and somnambulism occur rarely. Tolerance, withdrawal and rebound do not generally occur at recommended doses. CONCLUSION: Suvorexant has not been trialled against other hypnotics, is expensive and its utility for insomnia in patients with psychiatric disorders is unknown. Currently, use of suvorexant could be considered where more established treatments are inappropriate.

Switching and stopping antidepressants.

Switching from one antidepressant to another is frequently indicated due to an inadequate treatment response or unacceptable adverse effects. All antidepressant switches must be carried out cautiously and under close observation. Conservative switching strategies involve gradually tapering the first antidepressant followed by an adequate washout period before the new antidepressant is started. This can take a long time and include periods of no treatment with the risk of potentially life-threatening exacerbations of illness. Clinical expertise is needed for more rapid or cross-taper switching as drug toxicity, including serotonin syndrome, may result from inappropriate co-administration of antidepressants. Some antidepressants must not be combined. Antidepressants can cause withdrawal syndromes if discontinued abruptly after prolonged use. Relapse and exacerbation of depression can also occur. Gradual dose reduction over days to weeks reduces the risk and severity of complications.