Triprolidine: first generation H1 antihistamine
Triprolidine is a classical first generation H1 antihistamine. The drug has been part of OTC cold remedies internationally for decades, often combined with pseudoephedrine (e.g. Actifed). In Germany triprolidine is less common in current practice; in many other countries it remains a popular option for short term treatment of allergic and cold related symptoms.
Like all first generation H1 antihistamines, triprolidine crosses the blood brain barrier and has sedative properties. Hence both indications as a sleep aid in some OTC products and limitations such as reduced fitness to drive.
Mechanism of action
Triprolidine is a competitive antagonist at the H1 receptor. Histamine is a central mediator of allergic reactions and is released from mast cells and basophils. Through H1 receptors in skin, mucosa and airways, histamine causes itch, increased mucus secretion, vasodilation with redness, sneezing and bronchial reactions.
By inhibiting H1 receptors triprolidine reduces these symptoms. The drug also acts on central H1 receptors via the blood brain barrier, leading to sedation, mild hypnosis and occasionally reduced nausea. Anticholinergic properties explain dry mouth, visual disturbance and constipation.
The half life is about 3 to 5 hours, requiring multiple daily doses.
Indications
- Allergic rhinitis: seasonal and perennial, short term symptom relief
- Allergic conjunctivitis and urticaria: as adjunctive therapy
- Cold symptoms: in combination with pseudoephedrine or codeine, mainly for runny nose and sneezing
- Motion sickness: in some countries off label
- Off label as a short term sleep aid: due to sedative effect
Dosing and administration
Adults and adolescents: 2.5 to 5 mg every 4 to 6 hours, up to 20 mg per day.
Children: reduced for age and weight; in Germany use in young children is not recommended.
Tablets are taken with water, regardless of meals. With sedation, do not take immediately before driving.
Duration: short term for acute symptoms, generally no longer than 7 days. For chronic complaints modern non sedating second generation antihistamines (loratadine, cetirizine, fexofenadine) are preferred.
Adverse effects
Very common: sedation, fatigue, concentration difficulties, slowed reactions, dry mouth.
Common: dizziness, headache, visual disturbance (accommodation), constipation, urinary retention, nausea.
Uncommon: paradoxical excitation in children and elderly, tachycardia, hypotension, rash, pruritus.
Rare: seizures at very high doses or in seizure disorder, allergic reactions, bone marrow depression, photosensitisation.
Important points:
- Fitness to drive markedly reduced, particularly at the start
- Higher risk of paradoxical excitation in children and elderly
- Anticholinergic effects can worsen narrow angle glaucoma, prostatic hyperplasia or reflux oesophagitis
Interactions
- Alcohol and other CNS depressants: additive sedation, respiratory depression at high doses
- MAO inhibitors: enhanced and prolonged anticholinergic and sedative effect
- Tricyclic antidepressants, antipsychotics, anticholinergics: additive anticholinergic effect
- Sympathomimetics (pseudoephedrine): sensible combination in cold preparations, caution in hypertension
Special considerations
Pregnancy: limited data, preferably avoid, particularly in the first trimester.
Breastfeeding: passage to milk possible with effect on the infant, so avoid.
Children under 6 years: not recommended in Germany, paradoxical reactions are more common.
Elderly: increased sensitivity, fall risk through sedation. PRISCUS list classifies many first generation antihistamines as potentially unsuitable.
Narrow angle glaucoma, prostatic hyperplasia, pyloric stenosis, reflux: caution or contraindication.
Patient communication: in chronic allergies modern non sedating second generation antihistamines are usually better suited. Triprolidine remains an option for occasional short term symptoms or in combination products with specific indications.
Related substances
- Cinnarizine, H1 antihistamine with additional anti vertigo effect
- Levocetirizine, modern second generation H1 antihistamine
- Fexofenadine, non sedating H1 antagonist
- Azelastine hydrochloride, topical antihistamine
Frequently asked questions
Why does triprolidine make me tired?
As a first generation antihistamine triprolidine crosses the blood brain barrier and also blocks central H1 receptors. Histamine is an important wakefulness neurotransmitter; its inhibition causes fatigue and sedation. In children and older patients paradoxical excitation can occur instead.
Are modern antihistamines better?
For chronic allergies usually yes. Drugs such as loratadine, cetirizine, levocetirizine and fexofenadine cross the blood brain barrier only marginally and cause clearly less sedation. Anticholinergic adverse effects are also lower.
Can I drive on triprolidine?
No, especially not at the start of therapy or with noticeable fatigue. Reaction speed is markedly reduced and accident risk is increased. Caution is also required with alcohol and other CNS depressants.
When is triprolidine sensible?
For short term allergic symptoms, cold complaints with runny nose and sneezing, or as a short term aid for sleep problems with mild allergic symptoms. In long term complaints a switch to modern antihistamines is sensible.
Sources
- BfArM German Federal Institute for Drugs and Medical Devices
- EMA European Medicines Agency
- AWMF guideline allergic rhinitis
- Gelbe Liste triprolidine monograph
Legal notice and disclaimer
The information on this page is provided for general information only and does not constitute medical advice, diagnosis or treatment recommendation. It does not replace advice from a qualified physician or pharmacist. Medicines should only be used on prescription or after dispensing by a pharmacist. All information is based on the product information available at the time of writing and on recognised scientific sources; the manufacturer's current product information always prevails. Sanoliste assumes no liability for completeness, timeliness or accuracy of the information presented. In a medical emergency call the European emergency number 112.