Antipruritic – Antihistamine
Action And Clinical Pharmacology: Trimeprazine is a propylamino phenothiazine derivative with reduced central activity and enhanced antihistaminic and antipruritic effects.
It is a potent histamine antagonist. Trimeprazine possesses sedative properties, and is active in suppressing apomorphine induced vomiting in the dog. No evidence of teratogenic effect has been demonstrated in animal studies.
Indications And Clinical Uses: Pruritus regardless of site or etiology. The control of cough of various etiologies and the relief of asthma like dyspnea.
Contra-Indications: States of CNS depression due to barbiturates, alcohol, narcotics or analgesics. Cases with a history of blood dyscrasias or severe allergic reactions related to trimeprazine or other phenothiazines.
Manufacturers’ Warnings In Clinical States: Occupational Hazards: Patients should be advised against driving or engaging in activities requiring complete mental alertness or physical coordination, until their response to the drug has been well established.
Pregnancy: Use in pregnant women is not recommended except when in the judgement of the physician it is necessary for the welfare of the patient.
Precautions: Trimeprazine should be used with caution when there is a risk of potentiating CNS depressant drugs such as opiates, analgesics, antihistaminics, barbiturates and alcohol. It should also be used with caution in patients with a history of convulsive disorders or liver disease, and in cases of jaundice.
Since phenothiazines are known to reverse the pressor effect of epinephrine, if hypotension should occur, epinephrine should not be used as it may depress further the blood pressure.
The drug should be used cautiously in severely ill or dehydrated children who are more susceptible to seizures associated with phenothiazines.
The antiemetic action of trimeprazine may obscure signs of intestinal obstruction or brain tumor.
Ingestion after meals prolongs absorption of the drug, thus reducing incidence of possible side effects.
Adverse Reactions: At recommended therapeutic dosages, trimeprazine is usually well tolerated. Side effects that are likely to occur may be listed as follows:
CNS: Drowsiness is the most common initial untoward reaction but tends to subside within 1 to 3 weeks. It occurs most frequently in older age groups, and often with daily doses of 30 mg or more. Its incidence and intensity can be minimized by starting at a low dosage, gradually increased, or by prescribing the drug after food to promote a more gradual absorption. Should drowsiness persist it can be alleviated by decreasing dosage.
Extrapyramidal symptoms such as tremor, spasticity, painful contractions of skeletal muscles, dystonias have rarely been noted. If a neuromuscular reaction occurs, medication should be stopped and not reinstituted in children or in pregnant patients, while in others it may be resumed later, at a lower dosage. After discontinuation of treatment, extrapyramidal symptoms usually subside gradually within 24 to 48 hours. If a counteractant is necessary, barbiturates or an antiparkinsonian agent may bring rapid relief.
Other infrequent side effects reported include disturbing dreams, elation, depression, and fainting.
Autonomic Nervous System: Dryness of mouth and nasal congestion are rare.
Gastrointestinal: Gastric upset, abdominal discomfort and nausea may occur but usually disappear after a few days of medication. A few cases of cholestatic jaundice have been reported.
Skin: Drug rash and dermatitis have been observed in very few patients.
Allergic or Toxic: Very rare cases of reversible agranulocytosis and leukopenia have been reported. This reaction has responded to immediate withdrawal of trimeprazine and administration of antibiotics and corticosteroids. Since most reported cases of agranulocytosis, associated with the administration of phenothiazines, have occurred within the first 10 weeks of treatment, patients on prolonged therapy should be observed for this reaction particularly during that period.
Symptoms And Treatment Of Overdose: Symptoms: Drowsiness, dizziness, dryness of mucous membranes and gastrointestinal upsets. Massive overdosage may result in oversedation, collapse and coma.
Treatment: There is no specific antidote and treatment should be symptomatic. Gastric lavage should be carried out and the stomach left empty. Centrally acting emetics will not help because of the antiemetic effect of trimeprazine. Keep a clear airway and maintain adequate hydration.
Avoid CNS stimulants which may cause convulsions (e.g. picrotoxin and pentylenetetrazol).
Should collapse occur, put the patient in the head down position; use norepinephrine in an i.v. infusion of dextrose in normal saline, but not epinephrine as it may further depress the blood pressure. The infusion must not be stopped abruptly, but the drip rate reduced gradually when the desired blood pressure is reached.
Like other phenothiazine derivatives, trimeprazine is not dialyzable, so that hemodialysis is unlikely to assist recovery from overdosage, unless some other agents (e.g. barbiturate), have been taken concurrently.
Dosage And Administration: The dosage may vary with patients. In most cases a low dosage is effective, but it should be adjusted according to the severity of the symptoms and the patient’s response. All doses are expressed in terms of trimeprazine base.
Adults: 2.5 or 5 mg twice daily after meals and 5 mg at bedtime. In predominantly nocturnal conditions, a single bedtime dose of 5 to 10 mg may be given.
Children (2 to 12 years): 2.5 mg or 5 mg at bedtime. If necessary, an additional dose of 2.5 mg twice a day after meals may be given. Daily dose should rarely exceed 15 mg.
Availability And Storage: Liquid: Each 5 mL of yellow liquid contains: trimeprazine base 2.5 mg (as the tartrate). Nonmedicinal ingredients: alcohol 95%, artificial chocolate flavor, artificial fruit flavor, ascorbic acid, citric acid, D&C Yellow No 10, purified water and sucrose. Alcohol: 0.6% v/v. Sucrose: 4.2 g/5 mL. Energy: 67.6 kJ (16.1 kcal). Tartrazine-free. Bottles of 500 mL.
Tablets: Each varnished, light pink tablet contains: trimeprazine base 2.5 or 5 mg (as the tartrate). Nonmedicinal ingredients: acetic anhydride, carnauba wax, cellulose, colloidal silicon dioxide, dicalcium phosphate, diethyl phthalate, FD&C Red No 3, FD&C Yellow No 6, magnesium stearate, sodium croscarmellose, sodium oleate, titanium oxide and zein. Tartrazine-free. Bottles of 100 (2.5 and 5 mg) and bottles of 500 (5 mg). (Shown in Product Recognition Section)
PANECTYL® Rhône-Poulenc Rorer Trimeprazine Tartrate Antipruritic – Antihistamine
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