Pheniramine And Phenylephrine

Uses

Pheniramine is a competitive H1 histamine receptor antagonist. Like other alkylamine antihistamines it is also antagonist of muscarinic cholinergic receptors and possesses local anesthetic properties. However, the concentration required for the latter effect is probably not achieved at therapeutic dose

Pheniramine Maleate is used for allergic conditions (hypersensitivity reactions) such as:

• Hay fever (pollinosis) with attacks of sneezing, itching, running of the nose, conjunctivitis.
• Urticaria with pruritus and reddening, wealing and swelling of the skin.
• Eczema of nervous origin (neurodermatitis) with pruritus.

Phenylephrine is an alpha-1 adrenergic agonist used in the management of hypotension, generally in the surgical setting associated with the use of anesthetics.

Phenylephrine injections are indicated to treat hypotension caused by shock or anesthesia, an ophthalmic formulation is indicated to dilate pupils and induce vasoconstriction, an intranasal formulation is used to treat congestion, and a topical formulation is used to treat hemorrhoids. Off-label uses include situations that require local blood flow restriction such as the treatment of priapism.

Pheniramine And Phenylephrine is also used to associated treatment for these conditions: Allergic Skin Reaction, Allergic urticaria, Anaphylaxis, Angioedema, Burns first degree, Common Cold, Congestion of the Conjunctivas, Dermatitis, Eczematous, Drug hypersensitivity reaction, Flu caused by Influenza, Insect Bites, Neurodermatitis, Ocular Irritation, Red eye, Seasonal Allergic Conjunctivitis, Sunburn, UrticariaAllergic Rhinitis (AR), Anorectal discomfort, Cold, Common Cold, Common Cold/Flu, Congestion of the Conjunctivas, Conjunctivitis allergic, Cough, Cough caused by Common Cold, Eye allergy, Eye redness, Fever, Flu caused by Influenza, Headache, Headache caused by Allergies, Headache caused by Common Cold, Headache caused by Pollen Allergy, Hemorrhoids, Hypotension, Irritative cough, Itching of the nose, Itching of the throat, Laryngotracheitis, Nasal Congestion, Nose discomfort, Ocular Inflammation, Ocular Irritation, Paroxysmal Supraventricular Tachycardia, Pollen Allergy, Respiratory tract congestion, Respiratory tract irritation, Rhinopharyngitis, Rhinorrhoea, Seasonal Allergies, Shock, Cardiogenic, Sinus Congestion, Sinus pressure, Sinusitis, Sneezing, Sore Throat, Tracheobronchitis, Upper respiratory tract hypersensitivity reaction, site unspecified, Vasomotor Rhinitis, Aching caused by Flu caused by Influenza, Bronchial congestion, Itchy throat, Minor aches and pains, Watery itchy eyes, Airway secretion clearance therapy, Antihistamine, Dilatation of the pupil, Vasoconstrictor in regional analgesia therapy

How Pheniramine And Phenylephrine works

Pheniramine competes with histamine for the histamine H1 receptor, acting as an inverse agonist once bound. The reduction in H1 receptor activity is responsible for reduced itching as well as reduced vasodilation and capillary leakage leading to less redness and edema. This can be seen in the suppression of the histamine-induced wheal (swelling) and flare (vasodilation) response. Inverse agonism of the H1 receptor in the CNS is also responsible for the sedation produced by first-generation antihistamines like pheniramine. The binding of pheniramine to H4 receptors, and subsequent inverse agonism, may also contribute to reduced itching by antagonizing inflammation.

Phenylephrine is an alpha-1 adrenergic agonist that mediates vasoconstriction and mydriasis depending on the route and location of administration. Systemic exposure to phenylephrine also leads to agonism of alpha-1 adrenergic receptors, raising systolic and diastolic pressure as well as peripheral vascular resistance. Increased blood pressure stimulates the vagus nerve, causing reflex bradycardia.

Dosage

Pheniramine And Phenylephrine dosage

Unless otherwise prescribed by the doctor, the following dosages are recommended for the different dosage forms:

Pheniramine Maleate Injection Solution: Except in life threatening conditions, the initial dose should be kept as low as possible: particularly in small children, a daily dose of 3 mg active substance per kg body weight should not be exceeded.

The following doses are administered once or twice daily:

• Adults and Young people aged 12 years or over:1.0-2.0 ml IV/IM.
• Children aged 1-2 years (about 11-14 kg body weight):0.5-0.7 ml IM only
• Children aged 3-5 years (about 20 kg body weight):0.8-1.3 ml IM only
• Children aged 6-11 years (upto about 25 kg body weight):1.0-1.5 ml IM only

Pheniramine Maleate Injection (45.5 mg/2 ml)

: This is administered to adults and young people aged 12 years or over either slowly by intravenous route (1 ml per minute) or intramuscularly. To infants and children up to 12 years old the injection must only be given intramuscularly. The recommended dose may be repeated at 12 hourly intervals until acute symptoms have subsided. Pheniramine Maleate can be combined with commercial calcium preparations but the compatibility should be tested in individual case.

Pheniramine Maleate Tablet (22.7 mg): In adults and young people of over 12 years of age it is advisable to begin treatment with 1 tablet 2-3 times daily after meals. If necessary, the daily dose may be increased to 2 tablets 3 times daily from the second day of treatment onwards.

Pheniramine Maleate Syrup (15 mg/5 ml): is particularly suitable for children. Children aged 1-3 years should receive half a measuring spoonful two or three times daily; children aged 4-12 years, 1 measuring spoonful 2 or 3 times daily; adults and young people 1-2 measuring spoonful of syrup twice or three times a day after meals. A daily dose of 3 mg/kg body weight must not be exceeded. Diabetics must bear in mind that Pheniramine Maleate Syrup contains carbohydrates which are equivalent to 1.75 gm glucose per measuring spoonful (5 ml)

Pheniramine Maleate RetardTablet (75 mg): The coated tablets have a prolonged action. In most adults and adolescent over 12 years of age 1 coated tablet taken after supper is sufficient to produce an antihistaminic effect that for up to 24 hours. Only in very resistant cases will it be necessary to give an additional coated tablet in the morning after breakfast. The tablets are swallowed whole with a little liquid.

Side Effects

Occasionally there may be drowsiness, gastrointestinal complaints, dryness of mouth, palpitation, urinary retention or hypersensitivity reactions. In isolated cases, higher doses may produce hallucinations, restlessness or confusion; in small children, agitation.

In patients with narrow angle-glaucoma a rise in intraocular pressure is possible, which makes opthalmologic control necessary.

Even if used according to prescription, these preparations may reduce alertness to such an extent that the ability to cope with street traffic or operate machinery is impaired.

Toxicity

Case reports involving pheniramine overdosage mention the rare possibility of arrythmias, cutaneous eruptions, and rhabdomyolysis with acute kidney injury. The administration of activated charcoal effectively prevents the absorption of pheniramine as it largely adsorbs to the charcoal, therefore this may be of benefit in cases of overdose if provided early after ingestion.

Patients experiencing and overdose may present with headache, hypertension, reflex bradycardia, tingling limbs, cardiac arrhythmias, and a feeling of fullness in the head. Overdose may be treated by supportive care and discontinuing phenylephrine, chronotropic medications, and vasodilators. Subcutaneous phentolamine may be used to treat tissue extravasation.

Precaution

During pregnancy and lactation, pheniramine should be used only if strictly indicated, and after considering the benifit/risk ratio for mother and child.

Interaction

The effect of drugs which act on the central nervous system (e.g. tranquilizers, sedatives, neuroleptic agents and MAO inhibitors) and of alcohol may be potentiated.

Volume of Distribution

The volume of distribution of phenylephrine is 340L.

Elimination Route

The administration of 30.5 mg of free base pheniramine resulted in a Cmax of 173-294 ng/L with a Tmax of 1-2.5 h.

Phenylephrine is 38% orally bioavailable. Clinically significant systemic absorption of ophthalmic formulations is possible, especially at higher strengths and when the cornea is damaged.

Half Life

The terminal half-life of pheniramine administered via IV is 8-17 h.

Intravenous phenylephrine has an effective half life of 5 minutes and an elimination half life of 2.5 hours.

Clearance

Phenylephrine has an average clearance of 2100mL/min.

Elimination Route

Pheniramine is eliminated by metabolism and via renal excretion. 24.3% of pheniramine is present in the urine as the parent drug.

86% of a dose of phenylephrine is recovered in the urine with 16% as the unmetabolized drug, 57% as the inactive meta-hydroxymendelic acid, and 8% as inactive sulfate conjugates.

Pregnancy & Breastfeeding use

Pregnancy Category C. Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Contraindication

Hypersensitivity to pheniramine. The Syrup is contraindicated in patients hypersensitive to Methyl Hydroxybenzoate and Propyl Hydroxybenzoate. Prostatic hypertrophy with residual urine formation.

Acute Overdose

Symptoms: Agitation and convulsions (especially in children), and restlessness, disorientation and hallucinations in adults. Accidental ingestion in small children has resulted in convulsions and in some cases fatal.

Treatment: No specific antidote; symptomatic and supportive. Gastric lavage may be useful for some time after ingestion. Do not use stimulants. Diazepam or short-acting barbiturates may be used to control convulsions. Vasopressors may be used for hypotension.

Storage Condition

Keep all medicines out of the reach of children. To be dispensed only on the prescription of a registered physician. Do not use later than the date of expiry.

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