Suvorexant (Belsomra)

What is suvorexant?

Suvorexant is known as Belsomra in the United States and Japan alike (ベルソムラ on Japanese packaging). It's a newer type of sleep medicine called an orexin receptor antagonist: instead of sedating the whole brain, it blocks orexin, the brain's wake-promoting messenger, so the brain can shift from wakefulness to sleep.

How is it different from other sleeping pills?

• Dependence and tolerance are unlikely: in the trials, stopping it didn't cause withdrawal symptoms, and it kept working over months without the dose going up
• Blocks the wake signal rather than sedating the brain as a whole: a different way of working from benzodiazepine and Z-drug sleeping pills
• Helps with both falling asleep and staying asleep
• Not a controlled medicine in Japan: ordinary import rules apply when travelling, and the in-person-first rule for online prescribing doesn't apply to it

What is it used for in Japan?

Insomnia: both falling asleep and staying asleep.

What it targets: the whole night. By blocking the wake signal, it helps with getting to sleep and with staying asleep through the night.

How does it help?

By blocking the brain's wake signal at night, it makes it easier both to fall asleep and to stay asleep. It works from the first night, and it works best alongside good sleep habits.

What should I tell my doctor before starting?

A few situations rule it out entirely; your doctor will choose something else if any of these apply:

• A past allergic reaction to suvorexant
• Certain antifungals (such as itraconazole), antibiotics (clarithromycin, including the H. pylori treatment packs that contain it), HIV and COVID antivirals (ritonavir, Paxlovid, Xocova), and a few cancer medicines; the combination isn't allowed, so always tell us your full medication list, including short courses

And tell your doctor first if any of these apply; these usually just need adjustments or a closer eye:

• Heart or blood pressure medicines like diltiazem or verapamil, or the antifungal fluconazole; the dose may be kept lower with these
• Carbamazepine, phenytoin, or rifampicin, which can weaken its effect, or digoxin, whose level it can raise
• Narcolepsy or cataplexy
• Serious lung or breathing problems, including severe sleep apnea
• A past brain injury, stroke, or other brain condition (the effect can be stronger)
• Serious liver problems
• Other sedating medicines, or regular alcohol use
• Pregnant, planning to be, or breastfeeding (see the section below)

How do I take it?

Once a night, right before bed, and only on nights you can give a full night to sleep.

• Take it immediately before lying down; avoid taking it with or right after a meal, which can delay the effect
• If you forget it, just skip that night. Never take a second dose in one night
• Avoid alcohol; the Japanese label asks for this because the two add to each other's effects on alertness
• Older adults are prescribed a lower dose

What side effects should I expect?

Most are mild. Not everyone gets them.

• Sleepiness carrying into the next morning: the main one; if it happens, tell us, and don't drive while drowsy
• Headache
• Dizziness
• Tiredness
• Nightmares or unusual dreams

If anything is bothering you, tell your doctor; there's often a way to adjust.

Finally, one thing that is rare (most people never experience it) but good to know:

• A brief feeling of being unable to move while falling asleep or waking (sleep paralysis), or dream-like impressions at the edge of sleep. It passes on its own and isn't dangerous, but it can be startling; tell us and the plan can be adjusted

Will I become dependent? How do I stop safely?

Unlikely; in the trials, stopping it didn't cause withdrawal symptoms. It also kept working over months without the dose going up. The Japanese packaging still carries a standard notice that it may be habit-forming, so it is used at the prescribed dose and reviewed once sleep improves. The Japanese label asks for that review, so make any change together with your doctor rather than alone.

Can I drive while taking it?

No. Don't drive after taking it, and be alert to leftover drowsiness the next morning. The Japanese label instructs that patients on suvorexant shouldn't drive or operate dangerous machinery, because the effect can carry into the next day. If morning sleepiness keeps happening, tell your doctor; the dose or the medicine can be changed.

What about pregnancy and breastfeeding?

Tell your doctor early; this is decided case by case. The Japanese label allows suvorexant in pregnancy only when the benefit is judged to outweigh the risk. With breastfeeding, it passes into milk in small amounts (under 1% of the mother's dose, by weight), and the label leaves the decision to be weighed individually. Don't start, stop, or continue on your own. Our guides to medication in pregnancy and medication while breastfeeding cover the wider picture.