Antihistamine-Types,Uses And Dosage.
Antihistamine are medicines that affects the body in several ways :
- They help calm or prevent allergic reactions such as itchy rashes or lumps on the skin, hives, hay fever and allergic shock.
- They help prevent or control motion sickness or vomiting.
- They often cause sleepiness (sedation). Avoid doing dangerous work, operating machines or drinking alcohol when taking antihistamine.
Antihistamine of different types and uses.
Promethazine (Phenergan) and diphenhydramine (Benadryl) are strong antihistamines that cause a lot of sleepiness. Dimenhydrinate (Dramamine) is similar to diphenhydramine and is most used for motion sickness, promethazine often works better.
Chlorpheniramine is a less expensive antihistamine and causes less sleepiness. For this reason, it is sometimes best to use chlorpheniramine to calm itching in the day time. Promethazine is useful at night because it encourages sleep at the same time that it calms the itching.
There is no proof that the antihistamines do any good for the common cold. They are often used more than they need to be. Too much of it should not be used.
Antihistamines should not be used for asthma, because they make the mucus thicker and can make breathing more difficult.
One antihistamine is all that is usually needed in a medical kit. Promethazine is a good choice. Because it is not always available, doses for other antihistamines are also given.
As a general rule, antihistamines are best given by mouth. Injections should be used only to help control severe vomiting or before giving antitoxins (for tetanus, snakebite) when there is special danger of allergic shock. For children, it is often best to give a rectal suppository.
This medicine comes in tablets of 12.5 mg injections – ampules of 25 mg in 1 ml suppositories of 12.5 mg, 25 mg and 50 mg.
CAUTION : Pregnant women should only use promethazine if it is absolutely necessary.
Dosage of promethazine
1 mg/kg/day- using tablets of 12.5 mg. Give by mouth 2 times a day. In each dose, give :
- Adults : 25 to 50 mg (2 to 4 tablets)
- Children between 7 to 12 years old : 12.5 to 25 mg (1 or 2 tablets)
- Children between 2 to 6 years old : 6 to 12 mg (1/2 to 1 tablet)
- Babies of 1 year old : 4 mg (1/3 tablet)
- Babies under 1 year old : 3 mg (1/4 tablet)
Using intramuscular (IM) injections 25 mg in 1 ml. Inject once and again in 2 to 4 hours if necessary.
In one dose, inject :
- Adults : 25 to 50 mg (1 to 2 ml)
- Children between 7 to 12 years old : 12.5 to 25 mg (1/2 to 1 ml)
- Children under 7 years old : 6 to 12 mg (1/4 to 1/2 ml)
- Babies under 1 year old : 2.5 mg (0.1 ml)
Using rectal suppositories of 25 mg – Put high up in the rectum (anus) and repeat in 4 to 6 hours if necessary. In each dose, insert :
- Adults and children over 12 years old : 25 mg (1 suppository0
- Children between 7 to 12 years old : 12.5 mg (1/2 suppository)
- Children between 2 to 6 years old : 6 mg (1/4 suppository)
This medicine comes in capsules of 25 mg and 50 mg injections, ampules with 10 mg or 50 mg in each ml.
CAUTION : Do not give diphenhydramine to newborn babies or to women who are breast feeding. It is best not to use diphenhydramine in pregnancy unless is absolutely necessary.
Dosage of diphenhydramine
5 mg/kg/day – using capsules of 25 mg. Give 3 or 4 times a day.
- Adults : 25 to 50 mg (1 or 2 capsules)
- Children between 8 to 12 years : 25 mg (1 capsule)
- Children between 2 to 7 years old : 12.5 mg (1/2 capsule)
- Babies : 6 mg (1/4 capsule)
Using intramuscular (IM) injections, 50 mg in each ml.
Diphenhydramine should be injected only in the case of allergic shock. Inject once and again in 2 to hours if necessary :
- Adults : 25 to 50 mg (1/2 to 1 ml)
- Children : 10 to 25 mg depending on size (1/3 to 1/2)
- Babies : 5 mg (1/10 ml)
This often comes in 4 mg tablets and also tablets of other sizes, syrups etc.
Dosage for chlorpheniramine
Take 1 dose 3 or 4 times a day. In each dose, give :
- Adults : 4 mg (1 tablet)
- Children under 12 years old : 2 mg (1/2 tablet)
- Babies : 1 mg (1/4 tablet)
This medicine often comes in 50 mg tablets; also syrups with 12.5 mg in a teaspoon, also suppositories to put up into the anus. This is sold mostly for motion sickness but can be used like other antihistamines to calm allergic reactions and to encourage sleep.
Dosage of dimenhydrinate
Take up to 4 times a day. In each dose, give :
- Adults : 50 to 100 mg (1 or 2 tablets)
- Children between 7 to 12 years old : 25 to 50 mg (1/2 or 1 tablet)
- Children between 2 to 6 years old : 12 to 25 mg (1/4 to 1/2 tablet)
- Children under 2 years old : 6 to 12 mg (1/8 to 1/4 tablet)