Diphenylhydramine hydrochloride (tablets 0.05 g)

Tabulettae Dimedroli 0.05

International not patented name

Diphenhydramine

Pharmacotherapeutic group

H₁-antihistamine drugs. Sedative and soporific drugs.

Preparation composition

1 tablet contains 50 mg of diphenylhydramine hydrochloride (diphenhydramine).

Pharmaceutical action

Pharmacodynamics

The preparation exerts antihistamine, anti-allergic, anti-vomiting, soporific, local anesthetic effects. It blocks H₁–histamine receptors and eliminates the histamine effects caused through that type of receptors. It reduces or prevents the smooth muscles spasms caused by histamine, the capillaries permeability increase, tissues edema, itching and hyperemia. Antagonism with histamine is manifested mainly in relation to local vascular reactions in case of an inflammation and allergy as compared with the systemic ones, i.e. with arterial pressure lowering. It exerts local anesthesia (when taken orally a short time feeling of oral mucous membrane numbness), a spasmolytic effect, blocks the vegetative ganglia choline receptors (reduced arterial pressure). It blocks H₃–histamine cerebral receptors and suppresses the central cholinergic structures. It exerts sedative, soporific and anti-vomiting effects. It is more efficient in case of a bronchospasm caused by the histamine liberators (tubocurarine, morphine, sombrevine) and less efficient in case of an allergic bronchospasm. In case of bronchial asthma the preparation is low efficient and is used in combination with theophyllin, ephedrine and other broncholytics.

Pharmacokinetics

Taken inside it is absorbed well and quickly. Ninety eight – ninety nine percent of the drug taken is fixed with plasma proteins. The maximal plasma concentration (C_max) is achieved in 1 – 4 hours after being taken. The most of the diphenylhydramine hydrochloride taken is metabolized in the liver. The period of half elimination (T_1/2) is 1 – 4 hours. It is distributed widely in the organism, passes through the hematoencephalic barrier and placenta. It is excreted with milk and may cause a sedative effect in infants. Within 24 hours it is eliminated from the organism completely in form of benzhydrole conjugated with glucuronic acid and only a small quantity is excreted unchanged. The maximal effect is developed in 1 hour after being taken, the effect duration is 4 to 6 hours.

Indications

Urticaria, pollinosis, vasomotor rhinitis, itching dermatoses, acute iridocyclitis, allergic conjunctivitis, angioneurotic edema, capillary toxicosis, serum disease, allergic complications under medicamentous therapy, blood and blood substituting liquids transfusions; complex therapy of anaphylactic shock, of radiation sickness, of bronchial asthma, of the stomach ulcerous disease and of hyperacid gastritis; common colds, sleep disturbances, pre-medication, extended traumas of skin and soft tissues (burns, crushing); parkinsonism, chorea, sea and aviators’ sickness, vomiting, Menier’s syndrome; local anesthesia in patients having had allergic reactions to local anesthetic preparations in the anamnesis.

Mode of application and dosage

The preparation is taken inside. It is prescribed to adults in doses of 30 – 50 mg 1 – 3 times a day, the therapeutic course being 10 – 15 days. In case of a motion sickness the preparation should be taken in a single dose of 30 – 50 mg 30 – 60 minutes before going for prophylaxis; in case of insomnia it is taken in a dose of 30 – 50 mg before going to sleep. The maximal single dose is 100 mg, the maximal 24 hours dose is 250 mg. The preparation is prescribed to children aged 6 – 12 years in doses of 15 – 30 mg for an intake.

Special warnings

The preparation should be prescribed carefully to persons with hypothyroidism, an increased intraocular pressure, cardiovascular system diseases, in the elderly age. It should not be taken when driving and by the persons their professional occupation requires an increased concentration of attention. During the treatment period alcohol intake should be excluded.

Side effects

Nervous system and sensation organs: common weakness, fatigue, sedative effect, attention reduction, dizziness, sleepiness, headache, movements coordination disturbances, anxiety, increased excitability (in children particularly), irrirability, nervousness, insomnia, euphoria, mental confusion, tremor, neuritis, convulsions, paresthesia; vision disturbances, diplopia, acute labyrinthitis, noise in the ears. It activates (even taken in low doses) convulsive reactions at the EEG and may provoke epileptic attacks in persons with local cerebral damages and in epileptic persons.

Cardiovascular system and blood: hypotension, heart beating, tachycardia, extrasystole, agranulocytosis, thrombocytopenia, hemolytic anemia.

Gastrointestinal tract organs: xerostomia, short time oral mucous membrane numbness, anorexia, nausea, epigastral distress, vomiting, diarrhea, constipation.

Genitourinary system: frequent and/or dysuria, retention of urination, early menstruation.

Respiratory system: xeromycteria and xeropharyngia, nasal obstruction, bronchi secretion thickening, thorax obstruction and difficult breathing.

Allergic reactions: eruption, urticaria, anaphylactic shock.

Other side effects: sweating, shivering, photosensitivity.

Contraindications

Hypersensitivity, breastfeeding, childish age (newborns and pre-term newborns), close-angle glaucoma, prostate hypertrophy, stenosing gastric and duodenal ulcers, pyloroduodenal obstruction, stenosis of the neck of the gallbladder, pregnancy, bronchial asthma.

Interactions with other drugs

Soporific and sedative drugs, tranquillizers and alcohol enhance the central nervous system suppression (and vice versa). The MAO inhibitors enhance and prolong the chinolytic effects.

Overdosing

Symptoms: xerostomia, difficult breathing, persistent mydriasis, face reddening, CNS suppression or anxiety (in children more frequently), mental confusion; in children – convulsions development and lethal outcome.

Treatment: vomiting induction, stomach washing, activated charcoal prescription; symptomatic and supportive therapy under thorough control of breathing and arterial pressure values.

Dosage form

Tablets, 50 mg. Ten tablets in a contour not cellular pack or 10 tablets in a contour cellular pack.