Thanks for your replies.
I've now found this study (copy n pasted below) that suggests 5 mg is inferior than 10 mg when concerning time taken to fall asleep.
" Olanzapine
At doses of 5 to 20 mg/day, olanzapine is FDA approved for the treatment of schizophrenia and bipolar I disorder (mixed or manic episodes) in adults, as well as depressive episodes associated with bipolar I disorder and treatment resistant depression in adults when used in combination with fluoxetine.
27 Olanzapine's antagonist activity at 5-HT2A/2C, H1, muscarinic, and α1 receptors is believed to play a role in its sedative properties.
28,29 While serious cardiovascular complications associated with olanzapine are infrequent, significant weight gain, dyslipidemia, and glucose dysregulation are commonly associated with this atypical antipsychotic.
27 As with quetiapine, tardive dyskinesia and extrapyramidal adverse effects are uncommon with olanzapine. The most common adverse reaction observed in placebo-controlled trials of olanzapine is somnolence and olanzapine has been shown to affect sleep architecture.
27–29
Compared to placebo, significant increases in TST (p<0.01), sleep efficiency (p<0.01), SWS(p<0.05), and percent REM sleep (p<0.05) and decreases in wake time (p<0.01) were observed in a randomized, double-blind, placebo-controlled, cross-over, clinical trial evaluating the effects of a single morning dose of olanzapine 5 mg on objective and subjective sleep variables in 17 healthy volunteers.
28 A second randomized, placebo-controlled, double-blind, cross-over study compared placebo, olanzapine 5 mg and 10 mg in 9 healthy male patients (age range 33 to 60 years; mean age 45.3 years).
29 Single oral doses of olanzapine or placebo were administered 4 hours before bedtime over 3 nights, with each treatment separated by 7 to 14 days. Home-based PSG sleep recordings indicated that compared to placebo, olanzapine 5 mg and 10 mg produced significant increases in actual sleep time (p<0.005 and p<0.05, respectively), sleep efficiency (p<0.005 and p<0.05, respectively), and SWS (p<0.005, both doses); significant increases in subjective sleep quality were also observed (p<0.05, both doses). Olanzapine 10 mg was significantly better than olanzapine 5mg at decreasing sleep latency (p<0.05) and only the 10 mg dose was significantly better than placebo at decreasing REM sleep (p<0.005) and increasing REM latency (p<0.005).
29
Olanzapine, in doses ranging from 2.5 mg to 10 mg, was evaluated in a case series that included 9 patients with chronic insomnia secondary to various causes.
3,30 Eight of the nine patients experienced improved sleep parameters (measured by PSG) that included improved SL (n=3), a “feeling of good sleep” (n=2), an increase in TST (n=3), a decrease in nightmares (n=1), and unspecified improvement (n=3). Five of the eight patients received olanzapine as monotherapy. One patient experienced no improvement in sleep.
3,30
The effects of olanzapine were evaluated over a 3 week period in 12 patients experiencing insomnia and major depressive disorder unresponsive to therapy with therapeutic doses of citalopram, fluoxetine, paroxetine, sertraline, or venlafaxine.
31 Olanzapine was started at 2.5 mg nightly and increased to a maximum of 10 mg, as needed (mean dose 4.8 mg). Sleep parameters were measured using home PSG recordings at baseline, on night one of olanzapine treatment, and at the completion of the 3 week study period. In addition, after each of the 3 study nights, patients were asked to subjectively evaluate sleep quality based on “how well they had slept” using a 5 point scale where 1 indicated “much better than usual” and 5 indicated “much worse than usual”. The addition of a nightly dose of olanzapine significantly improved actual sleep time (p<0.001 night 1, p<0.01 at 3 weeks), sleep efficiency (p<0.001 night 1 and at 3 weeks), total WASO (p<0.01 night 1 and at 3 weeks), and subjective sleep quality (p<0.01 night 1, p<0.05 at 3 weeks). Significant improvements in SWS (p<0.01) and SL (p<0.05) were seen after 3 weeks of olanzapine treatment. Adverse effects were not reported in this study, but the authors do note patients reported olanzapine as being highly sedating and were unable to maintain a consistent morning rising time for the second and third PSG recordings. Weight was not measured.
31 "
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