Allergy (antihistamines) preparations 1, 2 and 3rd generation
Today allergic disease called civilization. According to the WHO, in urovnyu incidence of allergy takes third place among the other nosology. According to statistics, in the world today some form of allergic diseases suffered 20-40% of the population, that is, at least, every 5th inhabitant of the planet - have allergies. Today > 40% of the world population has a history of allergies. Every 10 years the number of Pacitients with allergic doubles. It is predicted that in the coming decades, each inhabitant of the Earth will suffer allergic disease. According to official data, in Russia allergy was diagnosed in 1.5% of the population. However, the real figures are much higher - up to 25%.
A significant prevalence of allergic diseasesThe created conditions for the rapid development of the field of pharmacy such as the development of anti-allergic drugs. Moreover, the prevalence of various forms of allergic diseases is becoming a pandemic. That is why there is a very widely used anti-allergic drugs, which, of course, a prerequisite for the emergence ofcases their irrational reception. Consequently, the increased frequency and severity of side effects antiallergic agents.
There are many varieties of antihistamines, but none of them have accepted. According to the classification proposed by the European Academy of Allergology and Clinical Immunology, all antigistaminnye drugs are divided into drugs « old » and « new » generation. They differ in the mechanism of action, the degree of affinity for the H1 receptor, the incidence and severity of side effects, have a different pharmacokinetic profile. Furthermore, time is divided into creation of preparations 1, 2 and 3generation.
Allergy drugs I generation
Preparations 1st generation is also called sedatives (according to the dominant side effects), and the preparations of the 2nd generation are called non-sedating vice versa. By the 3rd generation include the latest drugs - drugs active metabolites of the 2nd GenerationI and a therapeutically active enantiomers (chirally pure molecules) which exhibit the highest antihistamine activity and thus deprived of sedation and cardiotoxic action inherent in drug 2nd generation.
antiallergic drugs are classified according to their chemical structure. All of them arethe nitrogenous bases which contain an aliphatic side chain structure (as histamine molecules) ethylamine was substituted, and this ensures their antihistaminic activity. All preparations Allergy 1st generation (phenothiazines, ethanolamines, ethylenediamines, piperazines piridoindoly, piperidines) than H1 and muscarinic blocking,cholinergic, serotonin receptors. This creates additional pharmacological effects (sedative, anxiolytic, antitussive, local anesthetic, antiemetic, antimigraine etc.). The disadvantages of antihistamines 1st generation are: the emergence of the phenomenon of tachyphylaxis, which makesneed for replacement due to decreased effectiveness of drugs during their prolonged use. In favor of funds 1st generation indicates the presence of topically and injectable dosage forms that allows to apply them locally (for burns, insect bites), in the treatment of terminal states (angioedema, anaphylactic shock)As well as long-term (over 50 years) experience in the application, resulting in predictable pharmacological and side effects.
Allergy drugs II generation
Antihistamines 2nd generation (azetidinyl, alkylamines, piperazines, quinuclidine, triprolidine oxatomide, -phthalazinon, oksipiperaziny, ethylester, piperidines, piperidinimidazolony) appeared on the pharmaceutical market in the 1980s. They are uncompetitive and slowly bind to H1-receptors, which allows you to assign these drugs 1 - 2 Island twice a day, apply their long courses without compromising efficiency. However, astemizole and terfenadine are able toyzvat fatal arrhythmia type pirouette, cumulated in the body, which can lead to severe side effects. In the application of these drugs should be taken into account interactions with other drugs (inhibitors of cytochrome P450, namely the macrolides, antifungal agents, etc.).
Drugs 2nd generation (loratadine and tsetirIsigny) have a favorable pharmacokinetic profile (multiplicity of reception - 1 times per day), do not have cardiotoxic and sedation. Furthermore, they have a large number of generic versions, which greatly reduces the cost of medicines and makes them available to most patients.
Allergy preparaYou Generation III
Antihistamines 3rd generation - is active metabolites of drugs the previous generation. They are characterized by:
- fast absorption and distribution in the targeted organs;
- high bioavailability;
- long half-life that allows a single dose effect and saves up to 24 hours;
- additional anti-inflammatory activity;
- no clinically significant interactions with other drugs;
- no tachyphylaxis;
- in patients with impaired renal and hepatic function there is no need for dose adjustment.