Summary of Product Characteristics (SmPC) - Histalix syrup
1 NAME OF THE MEDICINAL PRODUCT
Histalix Syrup
2 QUALITATIVE AND QUANTITATIVE COMPOSITION
Each 5ml contains :-
Diphenhydramine HCl 14.00 mg
Ammonium Chloride 135.00 mg
Levomenthol 1.10 mg
Excipient(s) with known effect:
Sucrose 1.66g/5ml
Ponceau 4R (E124) 0.33mg/5ml
Propylene Glycol 0.5ml/5ml
Nipastat 6mg/5ml
Glycerin (also known as Glycerol) 0.75ml/5ml
For full list of excipients, see section 6.1
3 PHARMACEUTICAL FORM
Oral solution
Appearance: clear red to maroon coloured syrup
4 CLINICAL PARTICULARS
4.1 Therapeutic indications
For the oral symptomatic relief of troublesome cough associated with upper respiratory tract congestion and aids restful sleep
4.2 Posology and method of administration
Posology
One to two 5ml spoonfuls to be taken every 4 hours
To aid sleep the patient may start with two 5ml spoonfuls at bedtime followed by two 5ml spoonfuls every 6 hours.
Not suitable for children under 12 years.
Do not take more than 4 doses (1 dose = two 5ml spoonfuls) in 24 hours.
Do not exceed the stated dose.
Method of Administration
Oral
4.3 Contraindications
Hypersensitivity to the active substance(s) or to any of the excipients listed in section
6.1.
- Children below 12 years of age
Patients on monoamine oxidase inhibitor therapy within previous 14 days
(see section 4.5)
4.4 Special warnings and precautions for use
Do not combine with other treatments for coughs and colds.
Histalix syrup should be used with caution in patients with the following conditions: prostatic hypertrophy, urinary retention, susceptibility to ‘closed angle’ glaucoma and hepatic disease.
Histalix Syrup may cause drowsiness.
Seek medical advice when suffering from chronic or persistent cough and when also suffering from asthma, and acute asthmatic attack or where cough is accompanied by excessive secretions
Keep out of the reach and sight of children.
Ponceau 4R may cause allergic reactions.
Glycerol may cause headache, stomach upset and diarrhoea.
Parahydroxybenzoates may cause allergic reactions (possible delayed)
This medicine contains 0.5ml Propylene Glycol per 5ml dose. If you are pregnant or suffer from a liver or kidney disease, do not take this medicine unless recommended by your doctor. Your doctor may carry out extra checks while you are taking this medicine
Sucrose: Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.
4.5 Interaction with other medicinal products and other forms of interaction
- Additive CNS depressant effects with alcohol and other CNS depressants including barbiturates, hypnotics, opiod analgesics, anxiolytic sedatives and anti-psychotics.
- Additive anti-muscarinic effects with other drugs of similar properties such as atropine and some anti-depressants.
- Not to be taken in patients taking monoamine oxidase inhibitors (MAOIs) or within 14 of stopping treatment as there is a risk of serotonin syndrome.
- Diphenhydramine can inhibit the oxidative metabolism of some drugs.
- Diphenhydramine may enhance the effects of ephedrine.
- Diphenhydramine may mask the response of the skin to allergenic skin tests and also the ototoxic symptoms associated with certain antibiotics.
4.6 Fertility, pregnancy and lactation
Pregnancy
In view of the potential risks versus small benefits, it is recommended that Histalix syrup should not be used during pregnancy particularly as the safety of Histalix in human pregnancy is not established.
Lactation
In view of the potential risks versus small benefits, it is recommended that Histalix syrup should not be used during lactation particularly as the safety of Histalix in human pregnancy is not established
4.7 Effects on ability to drive and use machines
Histalix syrup may cause drowsiness. Do not drive or operate machinery. Avoid alcoholic drink.
4.8 Undesirable effects
The overall percentage of treated patients expected to experience adverse reactions is unknown.
Common side effects include:
CNS effects such as nervous drowsiness (usually diminishes within a few days), paradoxical stimulation, nervous headache, nervous psychomotor impairment.
Anti-muscarinic effects such as urinary retention, dry mouth, blurred vision, gastrointestinal disturbances and thickened respiratory tract secretions.
Rare side effects include:
Hypotension, extrapyramidal effects, dizziness, confusion, depression, sleep disturbances, tremor, convulsions, palpitation, arrhythmia, hypersensitivity reactions, blood disorders and liver dysfunction.
Organ system Class | Common ADRs, >1/100, < 1/10 | Uncommon ADRs, >1/1,000, <1/100 | Rare ADRs >1/10,000, <1/1000 |
Blood Lymphatic System Disorder | Blood Disorders NOS | ||
| Cardiac Disorder | Palpitation, arrhythmia | ||
| Eye Disorders | Blurred vision | ||
| Gastrointestina l Disorder | Dry mouth, gastrointestinal disturbance | ||
| General Disorder | Paradoxical drug reaction | ||
| Hepatobiliary Disorder | Liver Disorder | ||
| Immune System Disorders | Hypersensitivity | ||
| Nervous System Disorders | Psychomotor skills impairment, drowsiness, headache | Tremor, convulsions, extrapyramidal disorder, dizziness |
Organ system Class | Common ADRs, >1/100, < 1/10 | Uncommon ADRs, >1/1,000, <1/100 | Rare ADRs >1/10,000, <1/1000 |
| Psychiatric Disorders | Confusion, depression, sleep disturbances | ||
| Renal and Urinary Disorder | Urinary retention | ||
| Respiratory Disorder | Increased upper airway secretion | ||
| Vascular Disorders | Hypertension |
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme, Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store
4.9 Overdose
Symptoms of overdosage include those due to diphenhydramine or levomenthol (drowsiness, dizziness, ataxia, anti-cholinergic effects, pyrexia, headaches, convulsions, hallucinations, excitement and respiratory depression).
Treatment consists of gastric lavage and aspiration. Administration of activated charcoal may help. Other symptomatic and supportive measures should be provided.
5 PHARMACOLOGICAL PROPERTIES
5.1 Pharmacodynamic properties
Pharmacotherapeutic group: Antihistamines for systemic use
ATC Code: R06AA52
Diphenhydramine May suppress cough centre (mechanism unknown). Subjective relief of effects of allergic stimuli. Taken at night will assist sleeping
Ammonium Chloride "Traditional" Expectorant. May induce mild acidosis which is counteracted by the excipient sodium citrate.
Levomenthol Subjective relief of upper respiratory congestion. Whilst retained as a thick syrup in buccal cavity and throat provides cooling effect.
5.2 Pharmacokinetic properties
Diphenhydramine
Is a histamine receptor antagonist, Main site of metabolic transformation is the liver, Oral availability - 50%, Plasma bound - 80%, Half life - 4 hours
Ammonium Chloride
Effectively absorbed from GI tract.
Ammonium Ion converted to urea by the liver.
Acid ion released gives mild metabolic acidosis.
Levomenthol
After absorption Levomenthol is excreted in the urine and bile as a glucuronide
5 PHARMACOLOGICAL PROPERTIES
5.3 Preclinical safety data
There are no preclinical data of relevance, within are additional to those already included in other sections of the SmPC.
6 PHARMACEUTICAL PARTICULARS
6.1 List of excipients
Sucrose, Sodium Saccharin, Ponceau 4R (E124), Propylene Glycol, Raspberry Flavour, Nipastat (methylparahydroxybenzoate E218, ethylparahydroxybenzoate E215, propylparahydroxybenzoate E216, butylparahydroxybenzoate), Sodium Citrate, Glycerin, Purified Water.
6 PHARMACEUTICAL PARTICULARS
6.2 Incompatibilities
See Section 4.5
6.3 Shelf life
36 months
6.4 Special precautions for storage
Store below 30°C
6.5 Nature and contents of container
150ml Glass bottle.
Cap White PP28 TE CR with EPE/PE/AL/PET Wad
6.6 Special precautions for disposal
No special requirements
7 MARKETING AUTHORISATION HOLDER
Wallace Manufacturing Chemists Ltd
51-53 Stert Street, Abingdon, Oxfordshire, England, OX14 3JF
8. MARKETING AUTHORISATION NUMBER
PL 0400/0007R
9. DATE OF FIRST AUTHORISATION/RENEWAL OF THE AUTHORISATION
23rd June 1972, 1999
10 DATE OF REVISION OF THE TEXT
22/05/2025