Antihistamines are used to eliminate itching, which is one of the symptoms of allergies, eczema and other disorders. Sometimes, to relieve itching fairly regularly use moisturizers or point corticosteroids, but with complaints of severe itching, doctors usually prescribe antihistamines.
How do they work?
Antihistamines most commonly prescribed to alleviate the symptoms of allergies, such as hay fever. Antihistamines block the activity of histamine - a substance which is produced during defense reactions.
Histamine is stored in fat cells, which are in almost all tissues of the body. When an allergen enters the body, histamine is released. It binds to its receptors (H1 receptors). With this begins a chain reaction, during which increases blood flow to those areas which have contacted the allergen, and other chemicals are released, also are members of an allergic reaction, one of the consequences which it becomes itchy. Antihistamines relating to H1-blockers, according to its title, the H1 histamine receptors blocked, thus weakening the reaction and reduce itching.
By antihistamines also include H2 blockers (they reduce gastric acid secretion and are used for the treatment of certain diseases of the stomach) and H3 bloakatory - they are used to treat neurological diseases. Here we will talk about antihistamines that are H1-blockers.
Varieties antihistamines
Antihistamines are used to treat the symptoms of allergies, are divided into two groups: the old generation drugs having a sedative action, which affect the brain, causing drowsiness and the non-sedating antihistamines belonging to a new generation.
When allergy itching can occur throughout the day, one in the evening and at night, he usually gets worse or the patient pays more attention to it, because everyday activities at this time do not distract him from his own bodily sensations. Therefore, before going to bed
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recommended for the older generation antihistamines.
Day better than non-sedating antihistamines take such as cetirizine or loratadine. They cope well with itching in allergic reactions, but not effective in eczema.
Who does not fit antihistamines?
Antihistamines may cause deterioration in conditions such as glaucoma
Glaucoma - a perspective possible blindness
, Enlarged prostate, stagnation of urine or bowel obstruction. In these diseases, antihistamines should be used with caution.
Patients who have liver or kidney disease, you may need to take lower doses of antihistamines, although it largely depends on what kind of drug is given.
Pregnant women can take antihistamines only when absolutely necessary and only on a doctor's prescription and under his supervision.
Antihistamines may be given to young children, but with certain restrictions. Hydroxyzine is not recommended for children under six months, promethazine - children under the age of two years.
Sedating antihistamines can impair your ability to drive a vehicle, and perform tasks that require high concentration of attention. Alcohol increases the sedative effect of first-generation antihistamines, so during the course of treatment should be avoided. If you take this medication is very late at night, in the morning you may experience a condition similar to a hangover.
Side effects of antihistamines:
- Drowsiness
- Headache
- Blurred vision
- Constipation
- Dry mouth
- Dizziness
- Strangury
- Confusion
Drug Interactions
The following drugs can cause drowsiness, and therefore it is strongly not recommended to take with antihistamines:
- Tricyclic antidepressants such as amitriptyline
- Strong painkillers containing opioids, such as morphine, codeine, dihydrocodeine
- Benzodiazepines, such as diazepam, temazepam, lorazepam
- Hypnotics, such as zopiclone.
To reduce the risk of various side effects, you should not take antihistamines with antispasmodic, anticholinergic, and antipsychotics.
Three generations of antihistamines
Antihistamines include three generations of drugs, the first of which appeared in the vast pharmacy more in 1936.
- The first-generation is still successfully used for various therapeutic purposes. This notorious suprastin, diphenhydramine, tavegil, pipolfen and others. Despite the effectiveness of action, the first-generation drugs have significant drawbacks, such as the inhibition of the central nervous system, due to which the patient has excessive sleepiness, memory worsens dramatically reduced the rate of neuropsychiatric motor responses. For this reason, these drugs should not be given to people whose profession is connected with the need to control the situation and increased responsibility (motor vehicle drivers, pilots, dispatchers, operators of complex mechanical processes and so on). Other serious negative effects include the possibility of bronchospasm, a temporary decrease in blood pressure, impotence
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. Furthermore, long-term use is often sharp decline of therapeutic effect.
- More sophisticated products are considered second-generation antihistamines, which are at the same effectiveness have far fewer adverse events. Thus, they practically do not depress the central nervous system, and therefore do not exhibit typical first- generation inhibitory effect, at least in the appointment of dosage units. Furthermore, long-term supplementation did not reduce the effect of therapeutic action. However, when combined with anti-fungal medication means or macrolide antibiotics can not be excluded serious complications of cardiac activity, up to a cardiac arrest. The first second-generation drugs were released in the early 80-ies. This group includes terfenadine, Claritin
Claritin - histamine receptor blocker
, Gismanil and others.
- Optimal for appointment are third-generation antihistamines, which not only suppress the central nervous activity, but also safe in terms of cardiovascular performance. This group includes telfast, cetirizine, and others. Additional advantages of this group are more spectacular action and more rapid its manifestation. In addition, they are easily carried and do not interact with other drugs, can therefore be used for complex treatment of various diseases related.
