Somnil is doxylamine 25 mg, a sedating antihistamine sold as a sleep aid for short-term insomnia. It is available from a pharmacy without a prescription. It works, it is not a long-term solution, and tolerance to its sedating effect develops within days.
What is Somnil?
The South African Medicine Price Registry lists two presentations, both Schedule 2:
| Product | Form | Strength |
|---|---|---|
| Somnil | Tablet | Doxylamine 25 mg |
| Somnil (formerly Equi-Sleep) | Drops | Doxylamine 25 mg/ml |
Doxylamine is a first-generation antihistamine. Like the other older antihistamines, it blocks H1 histamine receptors — but unlike modern ones it crosses readily into the brain, where histamine is one of the signals that keeps you awake. Blocking it there produces drowsiness.
The sedation is the point here, not a side effect. Doxylamine is one of the most sedating antihistamines available, which is why it is sold as a sleep aid rather than as an allergy treatment, and why it also appears inside compound painkillers such as Tensopyn, Codoxol and Adco-Dol.
Two things follow, and both are important:
Tolerance develops quickly. The sedating effect diminishes within a few days to a week of nightly use. Taking it night after night stops working, and taking more to compensate simply increases the side effects.
It has a long half-life — around 10 hours. That is a large part of why people wake groggy, and it is why it should be taken with a full night ahead, not at two in the morning.
What is Somnil commonly used for?
- Short-term insomnia — difficulty falling asleep or staying asleep, for a few nights.
- Occasional sleeplessness from stress, travel, shift changes or a disrupted routine.
- Sleeplessness during a cold, where the antihistamine also dries a runny nose.
- Nausea and vomiting in pregnancy, where doxylamine combined with vitamin B6 is a well-established and specifically studied treatment — but that is a prescribed combination, and morning sickness treatment should be discussed with a doctor rather than self-started with a sleep product.
- Allergy symptoms, occasionally, though modern non-sedating antihistamines are better suited.
It is for a few nights, not for ongoing insomnia. That is not caution for its own sake — it is because tolerance makes it stop working, and because ongoing insomnia has causes that a sedating antihistamine does not touch.
What actually works for persistent insomnia is better established than most people realise: cognitive behavioural therapy for insomnia (CBT-I) has stronger and more durable evidence than any sleep medicine, and it is the recommended first-line treatment. Alongside it, the ordinary measures — consistent wake time, no screens late, no caffeine after midday, a cool dark room, getting out of bed if you cannot sleep — genuinely work, and they work permanently in a way that tablets do not.
Persistent insomnia is also frequently a symptom. Depression, anxiety, sleep apnoea, restless legs, chronic pain, thyroid problems and alcohol all cause it. A sleep aid taken indefinitely is how those go unexamined.
How Somnil fits into this medicine category
| Group | Examples | Notes |
|---|---|---|
| Sedating antihistamines | Doxylamine (Somnil), promethazine, diphenhydramine | Short-term sleep; rapid tolerance |
| Non-sedating antihistamines | Cetirizine (Austell Cetirizine), loratadine | Allergy without drowsiness |
| First-generation for allergy | Chlorphenamine (Rhineton) | Allergy, with sedation |
| Z-drugs | Zolpidem, zopiclone | Short-term insomnia; prescription; dependence risk |
| Melatonin | Melatonin | Circadian problems, jet lag, shift work |
| CBT-I | Behavioural therapy | First-line for persistent insomnia; most durable |
See the allergy, cold and flu medicines hub.
What to check before using Somnil
Check nothing else you take contains a sedating antihistamine. Doxylamine appears inside several common compound painkillers — Tensopyn, Codoxol, Adco-Dol — and cold and flu remedies frequently contain one too. Doubling up is easy and adds substantially to the sedation.
Speak to a pharmacist or doctor if you:
- Have glaucoma, particularly narrow-angle glaucoma.
- Have an enlarged prostate or difficulty passing urine — anticholinergic effects can cause acute urinary retention.
- Have asthma, COPD or breathing problems, or sleep apnoea. Sedatives worsen sleep apnoea, which is itself a common cause of poor sleep.
- Have epilepsy, liver disease or kidney disease.
- Take other sedating medicines — benzodiazepines, opioids, sleeping tablets, some antidepressants — or drink alcohol. The combination meaningfully increases the risk of dangerously slowed breathing.
- Take MAOI antidepressants.
- Are elderly. This matters: sedating antihistamines are on the list of medicines to avoid in older adults, because they cause confusion, dizziness and falls, and their anticholinergic effect adds to that of other medicines.
- Are pregnant or breastfeeding. Doxylamine has a specific role in pregnancy nausea, but that is a prescribed use — do not self-treat.
- Are giving it to a child. Sedating antihistamines are not appropriate as sleep aids for children.
Practical points:
- Take it shortly before bed, with a full night ahead — at least seven or eight hours.
- Do not drive the next morning until you know how it affects you. Next-day impairment is real, and it is the most under-appreciated risk.
- Avoid alcohol entirely.
- Use it for a few nights only.
Possible cautions and when to ask a pharmacist or doctor
Common effects are next-day drowsiness and grogginess, dry mouth, blurred vision, constipation, dizziness and difficulty passing urine. In some people — particularly children and older adults — sedating antihistamines cause the opposite: restlessness, agitation or confusion.
Get emergency help for:
- Very slow or shallow breathing, extreme drowsiness or difficulty being woken — particularly if alcohol or another sedative has been taken.
- Inability to pass urine, with a full painful lower abdomen.
- Severe eye pain, blurred vision with halos, and a red eye — possible acute angle-closure glaucoma.
- Confusion, hallucinations or marked agitation.
- Seizures.
- Swelling of the face, lips or tongue, or difficulty breathing.
Contact a doctor if:
- Insomnia persists beyond two weeks, or you are using a sleep aid most nights.
- You feel you cannot sleep without it.
- You snore heavily, gasp or stop breathing in your sleep, or wake unrefreshed despite enough hours — that suggests sleep apnoea, which sedatives make worse and which needs proper assessment.
- Sleeplessness comes with low mood, anxiety, or loss of interest in things.
- You have restless or twitching legs at night.
- You are elderly and having falls or confusion.
- Next-day grogginess is affecting work or driving.
Related medicine guides
- Browse Allergy, Cold & Flu Medicines guides
- Read: Austell Cetirizine used for
- Read: Rhineton used for
Frequently asked questions
What is Somnil used for? Short-term insomnia — difficulty falling or staying asleep for a few nights. It contains doxylamine 25 mg, a sedating antihistamine.
Do I need a prescription? No. It is Schedule 2, available from a pharmacy.
How long can I use it? A few nights. Tolerance to the sedating effect develops within days to a week, and it stops working.
Is it addictive? It does not cause dependence in the way benzodiazepines do, but people can become psychologically reliant on it, and tolerance develops quickly.
Will I feel groggy the next day? Often, yes. It has a half-life of around 10 hours. Take it with a full night ahead and do not drive until you know how it affects you.
Can I drink alcohol with it? No. The combination substantially increases sedation and the risk of slowed breathing.
Can older people take it? Cautiously, and preferably not. Sedating antihistamines cause confusion, dizziness and falls in older adults.
What works better for ongoing insomnia? Cognitive behavioural therapy for insomnia (CBT-I) has stronger and more durable evidence than any sleep medicine, and persistent insomnia is often a symptom of something treatable.