Synopen - Dose | Use | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Synopen is a medicine that contains the active substance chloropyramine. It belongs to the group of H1 antihistamines. Histamine is a substance which is released in allergic reactions. This medicine blocks the action of histamine and relieves allergy symptoms.

Due to this effect it is used to treat allergies include:

  • hives (urticaria),
  • insect sting allergy,
  • medications allergies,
  • hay fever and angioedema (swelling of the blood vessels).

This drug exists in the form of injections and an ointment. Injections are used for acute allergic reactions and anaphylactic shock. Synopen ointment is used in the treatment of insect bites and itching.


It cannot be used or can be used only with great caution in the following conditions:

  • If you are allergic to Synopen or another similar medications. Although synopen is medicine used in the treatment of allergies, still it can cause an allergic reaction. Allergy symptoms include:
    • swelling of the face,
    • swelling of the tongue,
    • swelling of the throat,
    • redness of the skin,
    • itching of the skin,
    • skin rash,
    • difficulty breathing. Immediately contact your doctor if you notice these symptoms.
  • Pregnant or breast-feeding. Tell your doctor if you are pregnant or breast-feeding.
  • Glaucoma (eye disorder, characterized as increased fluid pressure in the eye)
  • If you have an enlarged prostate
  • Asthma
  • If you suffer from epilepsy

Synopen should be used with caution in children and elderly.

Use during pregnancy and breast feeding

It is not recommended use of Synopen during pregnancy and breast feeding. It can be used during pregnancy only if the benefit to the mother outweighs the risk to the child.

Consult your doctor about using during pregnancy. Also avoid breast-feeding while using this medicine.

Use and Dose

Injections may be administered intramuscularly or intravenously.

The usual adult dose is 1 ampoule given as slow intravenous injection or as an intramuscular injection, 2-3 times a day.

The usual dose for children is ½ of ampoule given as slow intravenous injection or as an intramuscular injection.

Your doctor will decide how long you will use this medicine. It cannot be used in combination with alcoholic beverages. Ointment should be applied to the affected area in a thin layer. It should not cover large areas of skin. After you have applied the ointment on the affected area, wash your hands.

Synopen ointment is applied 2-3 times a day.


Symptoms of an overdose in adults are:

  • cardiovascular collapse,
  • drowsiness,
  • trouble breathing,
  • coma.

Symptoms of overdose in children are:

  • tremor (shaking) usually hands and feet,
  • fever,
  • ataxia (the presence of abnormal, uncoordinated movements),
  • hallucinations and other symptoms.

If you notice these symptoms, contact a physician immediately.

There is no specific antidote for Synopen overdose. Overdose should be treated symptomatically.

Use with other medications (Interactions)

Synopen cannot be used or can be used only with great caution with the following medications:

  • Medications used in the treatment of depression such as:
    • moclobemide,
    • selegiline,
    • tranylcypromine,
    • imipramine,
    • desimipramine,
    • amitriptyline,
    • nortriptyline and others.
  • Medications used in the treatment of severe pain, so-called narcotic medications such as:
    • morphine,
    • codeine,
    • pethidine,
    • tramadol and others.
  • Medications used in the treatment of anxiety such as:
    • sertraline,
    • fluoxetine,
    • fluvoxamine,
    • paroxetine,
    • citalopram,
    • escitalopram,
    • benzodiazepines (diazepam, bromazepam, alprazolam, midazolam, lorazepam) and others.
  • Phenobarbital, which is used in the treatment of epilepsy
  • Anesthetics.

All these medicines may increase the depressing effect of Synopen on nervous system and cause side effects.

Tell your doctor about all medications and herbal preparations you are taking.

It cannot be used in combination with alcoholic beverages.

Side effects

Synopen injections can cause the following side effects:

  1. headache,
  2. dizziness,
  3. fatigue,
  4. drowsiness,
  5. dry mouth,
  6. urinary retention,
  7. trouble urinating,
  8. nausea,
  9. vomiting,
  10. constipation,
  11. diarrhea,
  12. abdominal pain,
  13. hair loss (alopecia),
  14. insomnia,
  15. depression,
  16. increased intraocular pressure,
  17. muscle pain,
  18. tremors (shaking) usually hands and feet,
  19. convulsions,
  20. anemia,
  21. low white blood cell count,
  22. allergy and other side effects.

Ointment can cause the following side effect:

  • photosensitivity abnormally high sensitivity to sunlight.

Exposure to sunlight while using this medicament is not recommended.

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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