How many kinds of sleeping pill are there

Why the groups matter to a patient

Not so that you can choose for yourself, but so that you understand why a doctor asks carefully about the kind of insomnia you have before discussing medication. A short-acting drug suits someone who cannot FALL asleep; a longer-acting one suits someone who cannot STAY asleep. Used the wrong way round, it either does not last long enough or leaves you drowsy until midday.

The six groups

1. Benzodiazepines

The oldest group, acting broadly on the central nervous system through the GABA-A receptor. Sedating, anxiolytic and muscle-relaxing at once. That breadth of action is the source of both the effect and the problems: dependence, tolerance, rebound insomnia on stopping, and a risk of falls in older people.

2. Z-drugs, the non-benzodiazepines

Acting more selectively on part of the GABA-A receptor, so with less muscle relaxation and less anxiolytic effect. Very widely used. In 2019 the US drug regulator added a boxed warning to three drugs in this group because of complex sleep behaviours, walking, driving and cooking while not fully awake, which can lead to serious injury and death.

3. Dual orexin receptor antagonists

A newer group with an entirely different mechanism. Rather than suppressing the whole brain, it blocks orexin, the signal holding the brain in a waking state. Picture it this way: the older groups press the brake, this one lifts off the accelerator. In theory that produces sleep closer to the physiological kind.

4. Low-dose sedating antidepressants

Some antidepressants at very low doses have a strong antihistamine effect and are used for insomnia. The 2017 guideline weakly recommends one drug in this group for sleep maintenance, but does not recommend trazodone, even though it is very commonly prescribed for insomnia in many places.

5. Melatonin receptor agonists

Acting on the same receptor that endogenous melatonin binds to, but as prescription drugs with quite different pharmacokinetic properties from supplemental melatonin. Weakly recommended for trouble falling asleep.

6. Over-the-counter antihistamines and herbal products

This is the group patients self-medicate with the most and the one with the weakest evidence. International guidelines do not recommend diphenhydramine, melatonin, valerian or L-tryptophan for chronic insomnia. Antihistamines additionally carry an anticholinergic burden that matters in older people.

Summary table

Duration of action matters more than people think

Within the same group, differences in duration of action make a large difference to who a drug suits. A short-acting drug suits someone who cannot FALL asleep but sleeps afterwards; a longer-acting one suits someone who cannot STAY asleep.

Getting the direction wrong has two different consequences. A drug that is too short-acting for someone waking at 3am has already worn off before the problem happens. A drug that is too long-acting for someone who only struggles to fall asleep leaves them drowsy the next morning, with slowed reactions and a higher risk of falls, in older people above all.

Questions worth asking when you are prescribed something

1. Which part of my problem is this aimed at, falling asleep, staying asleep, or both?
2. How long am I expected to take it, and what is the plan for stopping?
3. Which unwanted effects should I know about, and which signs mean calling you straight away?
4. Does it interact with anything else I am taking?
5. If I want to reduce the dose later, how is that done?

The second question is the most important and the least often asked. A prescription for a sleeping pill with no plan for stopping very easily becomes a long-term prescription that nobody ever decided on.