Astemizole is the active ingredient in the antihistamine drug marketed under the name, Hismanal. It is a scored, white tablet designed for oral use. The usual recommended dose is 10 mg per day.
Like most antihistamine drugs, Astemizole acts by binding with the cell's histamine receptor sites, thereby blocking the ability of the cell to take in histamines. Astemizole specifically targets the H1 receptor sites of many of the body's organs, including the stomach, intestines and uterus.
The antihistamine also works in the bronchial muscles of the lungs where it prevents edema and pruritis, giving the sufferer relief from chest congestion.
The antihistamine also relieves itchy, watering eyes, runny nose, sneezing and swelling, itching skin. It is an effective treatment for hives but mostly used as a long-term medicine for Hay-fever or allergies.
The antihistamine was first developed in 1977 by the Janssen Pharmaceutica, a research and development subsidiary of Johnson and Johnson Corporation. At first, the antihistamine was well received because of its effectiveness and duration of action. It also does not cross the blood-brain barrier, and, therefore, does not reach the Central Nervous System and cause drowsiness the way many antihistamine drugs do.
Because of this, it is regarded as a part of a “second generation” series of antihistamine drugs that do not usually cause drowsiness or mental impairment. However, drowsiness has been noted as a possible side effect in some people.
The antihistamine was introduced in Canada as a prescription drug in 1984 and approved as an over-the-counter drug by 1986. In the United States, it was marketed as a prescription drug.
After years on the market, a rare but potentially deadly side effect was noted. A small number of people who took the antihistamine began to suffer from an irregular heartbeat, or arrhythmia. On some occasions this led to death.
In most cases, this side effect appeared as a result of elevated levels of the antihistamine in the blood. The consumer either took an overdose of the antihistamine, or was taking another drug which interacted with the Astemizole to raise its potency. Sometimes grapefruit juice was the trigger that elevated the antihistamine to deadly levels.
By 1992 Canada was restricting the use of the heretofore over-the-counter drug. By 1999 Johnson and Johnson voluntarily withdrew its brand of the antihistamine from the market. It is still available from some sources in its generic form.
Field testing has shown the antihistamine to also be a potent medicine for the treatment of malaria. However, it should not be taken along with any other antimalarial drugs. Additional research suggests that it might prevent muscle wasting or atrophy in long-term bedridden patients.
If you have been taking Astemizole and wish to continue taking it, you are warned to avoid taking it with anti-fungal drugs such as Nizoral, most proarrhythmogenic drugs and many antibiotics. This drug should not be taken with grapefruit juice. It should be taken on an empty stomach either an hour before eating or two hours after.