Allerplus - General Information
In the U.S., Allerplus was superseded by fexofenadine in the 1990s due to the risk of cardiac arrhythmia caused by QT interval prolongation.
Pharmacology of Allerplus
Allerplus, an H1-receptor antagonist antihistamine, is similar in structure to astemizole and haloperidol, a butyrophenone antipsychotic. The active metabolite of terfenadine is fexofenadine.
Allerplus for patients
Patient Package Insert
This leaflet is a summary of important information about terfenadine. Be sure to ask your doctor if you have any questions or want to know more.
What is Terfenadine and What is it Used For? Terfenadine is an antihistamine. It is used to relieve symptoms of seasonal allergies or hay fever. These symptoms include runny nose, sneezing, itching of the nose or throat, and itchy watery eyes.
Clinical studies conducted to date with terfenadine have not demonstrated effectiveness in relieving the symptoms of the common cold.
How Do I Take Terfenadine? Take terfenadine only as needed when you have symptoms of seasonal allergy or hay fever.
The recommended dose of terfenadine is one tablet taken twice a day. DO NOT TAKE MORE OFTEN THAN ONE TABLET EVERY TWELVE HOURS
Follow any other instructions your doctor gives you.
What Are the Important Warnings About Using terfenadine? WARNING: DO NOT USE TERFENADINE IF YOU ARE USING KETOCONAZOLE (NIZORAL), ITRACONAZOLE (SPORANOX), ERYTHROMYCIN, CLARITHROMYCIN (BIAXIN), OR TROLEANDOMYCIN (TAO). IF YOU HAVE ANY LIVER OR HEART PROBLEMS, TALK TO YOUR DOCTOR BEFORE YOU USE TERFENADINE.
Do not use terfenadine with any other prescription or nonprescription medicines without first talking to your doctor and pharmacist.
If you faint, become dizzy, have any unusual heartbeats, or any other unusual symptoms while using terfenadine, contact your doctor.
If you become pregnant or are nursing a baby, talk your doctor about whether you should take terfenadine. Your doctor will decide whether you should take terfenadine based on the benefits and the risks.
What Are the Risks of Using Terfenadine? The side effects which occur most often are headaches and mild stomach or intestinal problems.
In rare cases, terfenadine has caused IRREGULAR HEARTBEATS which may cause serious problems like fainting, dizziness, cardiac arrest, or death. In these rare cases, this occurred when terfenadine was taken:
in more than the recommended dose (remember, do not take more often than one tablet every twelve hours);
with the antifungal drugs ketoconazole (Nizoral), or itraconazole (Sporanox);
with the antibiotic drugs erythromycin, clarithromycin (Biaxin), or troleandomycin (TAO);
by patients with serious liver disease.
How do I Store Terfenadine? Terfenadine should be stored in a tightly closed container, in a cool place, out of direct sunlight. It should be kept away from children.
Spontaneous adverse reaction reports of patients taking concomitant ketoconazole with recommended doses of terfenadine demonstrate QT interval prolongation and rare serious cardiac events, e.g. death, cardiac arrest, and ventricular arrhythmia including torsades de pointes. Pharmacokinetic data indicate that ketoconazole markedly inhibits the metabolism of terfenadine, resulting in elevated plasma terfenadine levels. Presence of unchanged terfenadine is associated with statistically significant prolongation of the QT and QTc intervals.Concomitant administration of ketoconazole and terfenadine is contraindicated.
Torsades de pointes and elevated parent terfenadine levels have been reported during concomitant use of terfenadine and itraconazole in clinical trials of itraconazole and from foreign post-marketing sources. One death has also been reported from foreign post- marketing sources. Concomitant administration of itraconazole and terfenadine is contraindicated.
Due to the chemical similarity of other azole-type antifungal agents (including fluconazole, metronidazole, and miconazole) to ketoconazole, and itraconazole, concomitant use of these products with terfenadine is not recommended pending full examination of potential interactions.
Clinical drug interaction studies indicate that erythromycin and clarithromycin can exert an effect on terfenadine metabolism by a mechanism which may be similar to that of ketoconazole, but to a lesser extent. Although erythromycin measurably decreases the clearance of the terfenadine acid metabolite, its influence on terfenadine plasma levels is still under investigation. A few spontaneous accounts of QT interval prolongation with ventricular arrhythmia including torsades de pointes, have been reported in patients receiving erythromycin or troleandomycin.
Concomitant administration of terfenadine with clarithromycin, erythromycin, or troleandomycin is contraindicated: Pending full characterization of potential interactions, concomitant administration of terfenadine with other macrolide antibiotics, including azithromycin, is not recommended. Studies to evaluate potential interactions of terfenadine with azithromycin are in progress.
CONCOMITANT ADMINISTRATION OF TERFENADINE WITH KETOCONAZOLE (NIZORAL) OR ITRACONAZOLE (SPORONOX) IS CONTRAINDICATED. TERFENADINE IS ALSO CONTRAINDICATED IN PATIENTS WITH DISEASE STATES OR OTHER CONCOMITANT MEDICATIONS KNOWN TO IMPAIR ITS METABOLISM, INCLUDING SIGNIFICANT HEPATIC DYSFUNCTION, AND CONCURRENT USE OF CLARITHROMYCIN, ERYTHROMYCIN, OR TROLEANDOMYCIN. QT PROLONGATION HAS BEEN DEMONSTRATED IN SOME PATIENTS TAKING TERFENADINE IN THESE SETTINGS, AND RARE CASES OF SERIOUS CARDIOVASCULAR EVENTS, INCLUDING DEATH, CARDIAC ARREST, AND TORSADES DE POINTES, HAVE BEEN REPORTED IN THESE PATIENT POPULATIONS.
Terfenadine is contraindicated in patients with a known hypersensitivity to terfenadine or any of its ingredients.
Additional information about Allerplus
Allerplus Indication: For the treatment of allergic rhinitis, hay fever, and allergic skin disorders.
Mechanism Of Action: Allerplus competes with histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. This reversible binding of terfenadine to H1-receptors suppresses the formation of edema, flare, and pruritus resulting from histaminic activity. As the drug does not readily cross the blood-brain barrier, CNS depression is minimal.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Terfenadine
Drug Category: Antiarrhythmic Agents; Anti-Allergic Agents; Antihistamines
Drug Type: Small Molecule; Approved; Withdrawn
Other Brand Names containing Terfenadine: Aldaban; Allerplus; Cyater; Seldane; Teldane; Teldanex; Terdin; Terfex; Triludan;
Absorption: On the basis of a mass balance study using 14C labeled terfenadine the oral absorption of terfenadine was estimated to be at least 70%
Toxicity (Overdose): Mild (e.g., headache, nausea, confusion), but adverse cardiac events including cardiac arrest, ventricular arrhythmias including torsades de pointes and QT prolongation have been reported. LD50=mg/kg (orally in mice)
Protein Binding: 70%
Half Life: 3.5 hours
Dosage Forms of Allerplus: Tablet Oral
Chemical IUPAC Name: 1-(4-tert-butylphenyl)-4-[4-[hydroxy-di(phenyl)methyl]piperidin-1-yl]butan-1-ol
Chemical Formula: C32H41NO2
Terfenadine on Wikipedia: http://en.wikipedia.org/wiki/Terfenadine
Organisms Affected: Humans and other mammals