Terfenadine

Terfenadine is a H1-antagonist antihistamine that is similar in structure to astemizole. It, however, has a much shorter duration of action. Unlike other H1-antagonists, therapeutic doses of it produce insignificant anticholinergic activity or sedation, perhaps due to poor penetration of the drug into the CNS. It blocks the effects of histamine on H1-receptors in the GI tract, uterus, large blood vessels, and bronchial muscle. Blockade of H1-receptors also suppresses the formation of edema, flare, and pruritus that result from histaminic activity. At higher concentrations, H1-receptor antagonism becomes relatively irreversible. Terfenadine is used to provide relief from symptoms of allergies such as rash, hives, watery eyes, runny nose, itching eyes and sneezing, also used in skin allergies such as urticaria.

Terfenadine is primarily indicated in conditions like Advanced ovarian cancer, Allergy, Angioedema, Angioedema, Asthma, Conjunctivitis, Dermatitis, Lung cancer, Rhinitis, Urticaria.

Terfenadine

The severe or irreversible adverse effects of Terfenadine, which give rise to further complications include Allergic hepatitis. The signs and symptoms that are produced after the acute overdosage of Terfenadine include Convulsions, Ventricular arrhythmias. The symptomatic adverse reactions produced by Terfenadine are more or less tolerable and if they become severe, they can be treated symptomatically, these include Drowsiness, Fatigue, Alopecia, Photosensitivity, Burning, Depression, Angioedema, Desquamation.

Terfenadine should be used with caution in bone marrow depression. Patients should observe caution while driving or performing other task requiring alertness because it may cause drowsiness. It should be used with caution in patients with urinary retention, history of bronchial asthma, hyperthyroidism, cardiovascular or liver disease. It should be used with caution in person with acute or chronic respiratory impairment, especially in children. Do not administer S/C because irritation or lesion may occur.

Drug should not be given to Pregnant Mothers, patients suffering from Kidney dysfunction, patients suffering from Liver Malfunction, Geriatrics, and Neonates. If prescribing authority justifies the benefits of the drug against the possible damages he/she should reevaluate them and consult the reference material and previous studies.

0.86 to 1.71 mg/kg (1.3 (1.285)) 12 hourly PO — -

1.2 mg/kg (1.2 (1.2)) 12 hourly Oral — Recommended for 5-12 Yrs. Children

No neonatal dosage information is recorded for this medicine yet.

Terfenadine is known to interact with other drugs, the details of drug interactions is as follows:DrugDetailsSeverityOnsetManagementAlcoholAmiodarone (HCl)Amitriptyline (HCl)AmoxapineIncreased risk of ventricular arrhythmias when Amoxapine given with Terfenadine. ADVICE: Avoid concomitant use or only undertaken with caution and apprppriate monitoring.MajorAmprenavirIncreased risk of ventricular arrhythmias when Amprenavir given with Terfenadine. ADVICE: Avoid concomitant use.MajorArtemisininAstemizoleBoth drugs produce additive effect on cardiac conduction. Coadministration may prolong QT interval and may increase the risk of ventricular arrythmia.ModerateClinical monitoring is advised during concomitant administration. Patient should notify to physician if experience symptoms of torsade de pointes.AzithromycinConcomitant use of both drugs may cause QT-interval prolongation; increased risk of cardiac arrhythmias including ventricular tachycardia and Torsade de pointes. The risk of individual agent or combination of these agents causing ventricular arhythmia in association with QT-prolongation is largely unpredictable but may be increased by some underlying risk factors such as congenital long QT syndrome, cardiac disease and electrolyte disturbances (hypokalemia, hypomagnesemia). In addtion, the extent of drug-induced QT-prolongation is dependent on the perticular drug(s) involved and dosage(s) of the drug(s).Caution and clinical monitoring recommended.BendrofluazideBicalutamideADVICE: Avoid concomitant use with Terfenadine.MajorCarbamazepineCoadministration may increases free cabamazepine levels and clinical toxicity.ModerateClose monitoring for free level of cabamazepine must be done.CetirizineChlorothiazideChlorpheniramine (Maleate)Concomitant use of chlorpheniramine maleate and terfenadine increase the risk of palpitation.ChlorthalidoneCimetidine (HCl)Cimetidine prolong QT interval leads to ventricular arrhythmias by inhibiting CYP450 thus decreasing metabolism of terfenadine.MajorReplace with safer agent like loratadine or avoid this combination.CisaprideClarithromycinClarithromycin increases the plasma concentration of terfenadine by inhibiting CYP450 3A4-mediated first-pass metabolism result in high plasma level may be associated with prolongation of QT interval on the ECG, ventricular arrythmia, cardiac arrest and sudden death.MajorCoadministration is considered contraindicated. Loratadine, ctirizine, or fexofenadine is considered more safer than terfenadine and azithromycin and dirithromycin is consider more safer than clarithromycin.DimenhydrinateDocetaxelDothiepin (HCl)ErythromycinErythromycin increases the plasma concentration of terfenadine by inhibiting CYP450 3A4-mediated first-pass metabolism result in high plasma level may be associated with prolongation of QT interval on the ECG, ventricular arrythmia, cardiac arrest and sudden death.MajorCoadministration is considered contraindicated. Loratadine, ctirizine, or fexofenadine is considered more safer than terfenadine and azithromycin and dirithromycin is consider more safer than erythromycin.FluconazoleFluconazole increases the plasma concentration of terfenadine by inhibiting CYP450 3A4-mediated first-pass metabolism result in high plasma level may be associated with prolongation of QT interval on the ECG, ventricular arrythmia, cardiac arrest and sudden death.MajorCoadministration of terfenadine with higher doses of fluconazole is considered contraindicated. Loratadine, cetirizine or fexofenadine are safer alternatives of terfenadine.Halofantrine (HCl)HydrochlorothiazideConcomitant administeration can lead to prolong QT intervalIndinavir (Sulphate)Co administration increases the plasma concentrations by inhibiting the enzyme responsible for metabolic clearance.MajorCo administration is considered contraindicated.Loratadine,Cetirizine or Fexofenadine may be the safer alternatives during therapy.ItraconazoleKetoconazole Co-administration increases the plasma concentration, prolong QT interval, ventricular arrhythmia and cardiac arrest of terfenadine by inhibiting metabolic clearanceof terfenadine. MajorKetoconazole at multiple doses of 400mg or higher with Terfenadine is considered contraindicated.Loratidine,Cetrizine or fexofenadine are safer alternatives to use.Mibefradil (Di HCl)Miconazole (Nitrate)Nefazodone (HCl)Nefazodone inhibit the metabolism of terfenadine.result in increased plasma concentration of terfenadine may lead to prolonged QT interval, arrythmia and death.MajorCoadministration of these agents is considered contraindicated.NelfinavirNevirapinePentamidineConcomitant use of these drugs increase the risk of ventricular arrythmiaModerateClinical monitoring is advisable.PolythiazideRitonavirRoxithromycinSodium CromoglycateVORICONAZOLEIncreased risk of cardiotoxicity and arrhythmias These interactions are sometimes beneficial and sometimes may pose threats to life. Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.

Tab Store Below 40°C. Protect from Sunlight and Moisture.