Dimedrol

INSTRUCTIONS FOR MEDICAL USE OF THE MEDICINAL PRODUCT DIMEDROL (DIMEDROL)

Composition:

Active substance: 1 ml of solution contains 10 mg of diphenhydramine hydrochloride;

Excipient: water for injections.

Pharmaceutical form. Injection solution.

Main physicochemical properties: clear colorless liquid.

Pharmacotherapeutic group. Antihistamines for systemic use. ATC code R06AA02.

Pharmacological properties.

Pharmacodynamics.

A first-generation H1-histamine receptor blocker that counteracts the effects of histamine mediated through this type of receptor. The action on the central nervous system (CNS) is due to blockade of brain H3-histamine receptors and inhibition of central cholinergic structures. Has pronounced antihistamine activity, reduces or prevents histamine-induced spasms of smooth muscle, increased capillary permeability, tissue edema, itching, and hyperemia. Causes local anesthetic effect (after oral administration, transient numbness of oral mucosa occurs), blocks ganglionic cholinoreceptors (reduces arterial pressure (BP)) and CNS, exerts sedative, hypnotic, anti-Parkinsonian, and antiemetic effects. The antagonism with histamine is more pronounced regarding local vascular reactions in inflammation and allergy than regarding systemic effects, i.e., reduction of arterial blood pressure. However, when administered parenterally to patients with circulating blood volume deficiency, a decrease in BP and worsening of existing hypotension may occur due to ganglion-blocking action. In patients with localized brain damage and epilepsy, Diphenhydramine activates (even at low doses) epileptic discharges on EEG and may provoke epileptic seizures. It is more effective in bronchospasm caused by histamine liberators (tubocurarine, morphine) and less effective in bronchospasm of allergic origin. Sedative and hypnotic effects are more pronounced with repeated administration.

Pharmacokinetics.

Plasma protein binding – 98–99%. The majority is metabolized in the liver, while a smaller portion is excreted unchanged in urine within 24 hours. The elimination half-life (T1/2) is 1–4 hours. It distributes well throughout the body and penetrates the blood-brain barrier.

It is mainly metabolized in the liver via hydroxylation and conjugation to glucuronides; metabolites are eliminated in urine. It is excreted in breast milk and may cause a sedative effect in breastfed infants. Maximum activity develops within 1 hour; duration of action is 4 to 6 hours.

Clinical characteristics.

Indications.

Anaphylactic shock, urticaria, hay fever, serum sickness, hemorrhagic vasculitis (capillarotoxicosis), polymorphic exudative erythema, angioedema (Quincke's edema), pruritic dermatoses, pruritus, allergic conjunctivitis and other allergic eye diseases, allergic reactions associated with drug intake, chorea, Ménière’s disease, postoperative vomiting.

Contraindications.

Hypersensitivity to the drug. Acute bronchial asthma attack, pheochromocytoma, epilepsy, congenital long QT syndrome or prolonged use of drugs that may prolong the QT interval, closed-angle glaucoma, benign prostatic hyperplasia, stenosing peptic ulcer of the stomach or duodenum, bladder neck stenosis, bradycardia, cardiac arrhythmias. Porphyria.

Interaction with other medicinal products and other forms of interaction.

Diphenhydramine potentiates the effects of anesthetics, hypnotics, sedatives, narcotic analgesics, and local anesthetics. When used concomitantly with tricyclic antidepressants, an enhanced anticholinergic effect and CNS depression may occur. There is a risk of seizures when used simultaneously with analeptics. Concurrent use of MAO inhibitors and diphenhydramine may lead to increased blood pressure and adverse effects on the central nervous and respiratory systems. Concomitant use of diphenhydramine with antihypertensive agents may enhance feelings of fatigue. The drug enhances the effects of ethanol and reduces the efficacy of apomorphine as an emetic agent in poisoning treatment. It should not be administered together with products containing diphenhydramine, including those intended for topical use.

Special precautions for use

Not recommended for subcutaneous administration. Since Dimedrol has atropine-like effects, it should be used with caution in patients with a recent history of respiratory disorders (including asthma), increased intraocular pressure, hyperthyroidism, cardiovascular diseases, or arterial hypotension. It may worsen the course of obstructive lung diseases, severe cardiovascular disorders, ileus, and conditions involving biliary tract obstruction. Dimedrol may cause drowsiness and may also induce excitement, hallucinations, and seizures, especially in cases of overdose. Use with caution in patients aged 60 years and older due to a higher risk of developing dizziness, sedation, and arterial hypotension.

Use with caution in patients with impaired liver or kidney function.

During treatment with this medication, exposure to UV radiation and alcohol consumption should be avoided. Patients should inform their physician about using this drug, as its antiemetic effect may interfere with the diagnosis of appendicitis and recognition of symptoms related to overdose of other medicinal products.

Use during pregnancy or breastfeeding

Dimedrol is contraindicated during pregnancy due to insufficient data on the safety and efficacy of its use.

If treatment with this drug is necessary, breastfeeding should be discontinued.

Ability to affect reaction speed when driving or operating machinery

Since Dimedrol has sedative and hypnotic effects, patients should refrain from potentially hazardous activities requiring heightened attention and rapid psychomotor reactions during treatment.

Administration and Dosage

The drug is intended for intramuscular and intravenous drip administration in adults. Do not administer subcutaneously due to its irritant effect.

For intramuscular administration, the single dose is 10–50 mg (1–5 mL); the maximum single dose is 50 mg (5 mL), and the maximum daily dose is 150 mg (15 mL). For intravenous administration, the drug should be given by drip infusion at a dose of 20–50 mg (2–5 mL) of Dimedrol in 100 mL of 0.9% sodium chloride solution. The duration of treatment depends on the therapeutic response and the patient's tolerance to the drug.

Children

The drug must not be used in pediatric practice.

Overdose

Symptoms: dry mouth, respiratory depression, persistent mydriasis, facial flushing, central nervous system depression or excitation, depression, confusion, hyperkinesia, seizures, delirium, tachycardia, arrhythmia. A case of rhabdomyolysis following Dimedrol overdose has been reported.

Treatment: symptomatic and supportive therapy with careful monitoring of respiratory function and arterial pressure. Epinephrine and analeptics must not be used. Intravenous drip infusion of plasma substitutes and oxygen therapy are recommended. Physostigmine (0.02–0.06 mg/kg body weight intravenously) may be administered as an antidote in cases of diphenhydramine hydrochloride overdose, repeated as necessary if anticholinergic symptoms worsen. In cases of physostigmine overdose, atropine administration is recommended. Parenteral diazepam should be administered in the event of seizures or CNS excitation symptoms.

Adverse reactions.

Central nervous system and sensory organs: general weakness, fatigue, sedative effect, decreased attention, dizziness, drowsiness, headache, impaired motor coordination, decreased speed of psychomotor reactions, anxiety, increased excitability, fear of death, irritability, nervousness, insomnia, euphoria, confusion, tremor, neuritis, seizures, paresthesia, mydriasis, increased intraocular pressure, visual disturbances, diplopia, acute labyrinthitis, tinnitus. In patients with focal lesions or epilepsy, seizure discharges on EEG may be activated (even with low doses of Dimedrol), and the drug may provoke epileptic seizures.

Cardiovascular system: arterial hypotension, palpitations, tachycardia, extrasystoles.

Blood system: agranulocytosis, thrombocytopenia, hemolytic anemia.

Gastrointestinal tract: dry mouth, transient numbness of the oral mucosa, anorexia, nausea, epigastric pain, vomiting, diarrhea, constipation.

Genitourinary system: frequent and/or difficult urination, urinary retention, early menstruation.

Respiratory system: dryness of nasal and pharyngeal mucosa, nasal congestion, bronchial secretion thickening, chest tightness, dyspnea, shortness of breath.

Skin and its appendages: hyperemia, pruritus, polymorphic rashes, cyanosis of skin and mucous membranes.

Allergic reactions: rash, urticaria, anaphylactic shock.

Local reactions at injection site: local necrosis with subcutaneous and intradermal administration.

Other: increased sweating, chills, fever, hyperthermic syndrome, photosensitization.

Shelf life. 4 years.

Storage conditions. Store in original packaging at a temperature not exceeding 25 °C. Keep out of reach of children.

Incompatibility. The drug should not be mixed with other medicinal products in the same container. Use only the recommended solvent.

Packaging. 1 ml in a vial, 10 vials per box; 1 ml in a vial, 10 vials in a blister pack, 1 blister pack per carton.

Prescription status. Prescription only.

Manufacturer. JSC "Halychpharm".

Manufacturer's address and place of business.
79024, Ukraine, Lviv, Opryshkivska St., 6/8.