Sominex vs Nytol - sleeping pills reviewed

Sominex vs Nytol for sleeping

Sominex and Nytol are two brands of over the counter sleeping pills available in the UK. Sominex vs Nytol includes all necessary information to highlight similarities and differences between both drugs and consequently answer some practical questions, for example, what is the difference between both drugs, is Sominex better than Nytol?  

Sominex vs Nytol: legal classification

Sominex and Nytol - pharmacy only sleeping pills

In the initial paragraph, I named Sominex and Nytol as over the counter sleeping pills. Sominex and Nytol are classified as pharmacy-only medicines (P). P medicines can only be sold from pharmacies including online chemists. When sold in pharmacies, P medicines, cannot be available for patient self-selection, which means that Sominex and Nytol are kept behind the pharmacy counter. Additionally, when a request is made to purchase either of the products, a member of a pharmacy team may check the suitability of the requested drug with the pharmacist.

Who can/cannot use Sominex or Nytol?

All pharmacy-only medicines have a license attached, which defines who can or cannot use them. Very broadly, restrictions usually may relate to a patient’s age and their health ‘status’, for example existing comorbidities.

Age restrictions

Sominex tablets can only be used by adolescents who are 16 years of age and above.

Nytol on the other hand is restricted to adults who are 18 years of age and above.

The above age restrictions apply to the usage of both drugs and do not reflect the minimum age for the purchase of either of the drugs. There are no ‘official’ minimum age restrictions for purchasing Sominex or Nytol. Commonly pharmacy teams require a minimum age to be 16 when requesting to purchase medicines from a pharmacy. Because of the nature of both drugs, a pharmacist may refuse the sale to a young person wanting to buy either Nytol or Sominex. Refusal to sell any drug to any patient is within a pharmacist’s right.

Restrictions based on co-mobilities

 A number of contraindications apply to both sleeping tablets. Both Sominex and Nytol have additional specials precautions and warnings for their use. Please refer to product information leaflets or speak to your pharmacist.


  • Patients are sensitive to any substance found in tablets, including the main active ingredient
  • Patients on MOI (type of antidepressant) or who have stopped MOI within the last 14 days
  • Patients with any form of CNS depression


Nytol should not be used by the following patients:

  • Patients with stenosing peptic ulcer
  • Patients with pyloroduodenal obstruction
  • Patients with phaeochromocytoma (a rare type of tumour)
  • Patients with QT interval prolongation or at risk of QT prolongation, for example, some patients with cardiovascular disease, imbalance of electrolytes, patients with a family history of sudden cardiac death, significant bradycardia
  • Patients who take drugs known to prolong the QT interval or cause Torsade de Pointes

Restrictions on the duration of use

When purchased over the counter, Sominex and Nytol should not be used for longer than 7 days.

Sominex vs Nytol: main active ingredients

The main active ingredients found in Sominex and Nyol are classified as first-generation antihistamines. First-generation antihistamines produce significant drowsiness, therefore, very often in the UK are used as sleep aid medicines.

The main active ingredient found in Sominex is promethazine. The main active ingredient found in Nytol is diphenhydramine Hydrochloride.

Sominex vs Nytol: form availability

Nytol is available in form of tablets and liquid:

  • Nytol Orignial (each tablet contains 25mg of diphenhydramine)
  • Nytol One-A-Night (each tablet contains 50mg of diphenhydramine)
  • Nytol liquid (10mg of diphenhydramine per 5ml of liquid)

Each Sominex tablet contains 20mg of promethazine. Sominex tablets come only in one strength.

What is the difference between Sominex and Nytol?

As previously stated, both drugs contain a sedative antihistamine as the main active ingredient, promethazine in Sominex and diphenhydramine in Nytol. What difference does it make?

One way of looking at the difference between both drugs is by looking at the drug’s half-life, which defines the time to eliminate the drug from the boy (50% of it). Generally, drugs with a short half-life tend to work quickly with shorter effects on the body.

Diphenhydramine (Nytol) has a shorter ‘half-life’, which is approximately 9 hours (Huynh et al., 2021). Promethazine’s half-life is estimated to be 12-15 hours (Taylor et al., 1983).

Based on the above, Nytol has a shorter duration of action, which may cause less drowsiness in the morning.

Sominex takes 15-30 minutes to work with the highest concentration of drug in the body after 2-3 hours (eMC, 2020).

For Nytol, the maximum sedative effect is achieved within 1-3 hours (HPRA, N.D.).  

How long can you use over the counter Nytol or Sominex?

When purchased over the counter both Nytol and Sominex should not be used for longer than 7 days.

Sominex vs Nytol: side effect profile

Side effects which may be experienced by people taking Sominex or Nytol are similar since both drugs belong to the same group of drugs.

What are Sominex’s side effects?

Patients taking Sominex may experience possible side effects. Frequency is not known for the following side effects (eMC, 2020) :

  • Drowsiness
  • Dizziness
  • Dry mouth
  • Constipation (see: treatment of constipation with Laxido or Movicol)
  • Nausea (feeling sick), vomiting (being sick)

For a list of all possible side effects, please refer to the product information leaflet.

Nytol: common side effects

Common side effects possible with Nytol:

  • drowsiness,
  • sedation, disturbance in attention,
  • unsteadiness,
  • dizziness,
  • dry mouth
  • fatigue

Is Sominex or Nytol addictive?

Antihistamines are not considered to be addictive, however, they may be misused and abused, which may cause dependence. One of the highlights of dependence is tolerance, with a drug having a reduced ‘effect’ caused by repeated use.

Some studies showed that tolerance may develop quickly, for example in one study involving diphenhydramine, tolerance to the drug developed by day 3 of drug administration (Richardson et al., 2002).

Is Sominex better than Nytol?

Many customers ask about better or stronger sleeping pills when requesting over the counter sleeping aids. One cannot say that Sominex is better than Nytol and vice versa. Sominex may work for longer, causing more profound drowsiness, which may be experienced in the morning.

Alternative options to Sominex and Nytol

There are plenty of Nytol alternative products, which contain an equivalent amount of diphenhydramine, for example:

  • Numark Night Time Sleep Aid Tablets
  • NightAid
  • Boots Sleepeaze

Sominex does not have alternative medicines which contain the same amount of promethazine, however other sleep aids containing promethazine are sold in the UK, for example:

  • Phenergan 10 and 25mg mg tablets
  • Phenergan Elixir
  • Phenergan Night Time 25 mg tablets

Both promethazine and diphenhydramine are commonly added in ‘night’ versions of cold and flu remedies and cough medicines.


EMT (2020). SmPC: Sominex tablets. Available at: Accessed on 28/03/2022

Huynh DA, Abbas M, Dabaja A. Diphenhydramine Toxicity. [Updated 2021 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: Accessed on 28/03/2022

HPRA, N.D. Nytol One a night 50mg tablets: Summary of Product Characteristics. Available at: Accessed on 28/03/2022

Richardson GS, Roehrs TA, Rosenthal L, Koshorek G, Roth T. Tolerance to daytime sedative effects of H1 antihistamines. J Clin Psychopharmacol. 2002 Oct;22(5):511-5. doi: 10.1097/00004714-200210000-00012. PMID: 12352276. Available at: Accessed on 28/03/2022.

Taylor G, Houston JB, Shaffer J, Mawer G. Pharmacokinetics of promethazine and its sulphoxide metabolite after intravenous and oral administration to man. Br J Clin Pharmacol. 1983 Mar;15(3):287-93. doi: 10.1111/j.1365-2125.1983.tb01501.x. PMID: 6849764; PMCID: PMC1427776. Available at: Accessed on 28/03/2022

I am a qualified pharmacist working in an independent pharmacy in the UK.
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