Histamine and antihistaminic agents
Antihistamine:
• The drugs which abolish or diminish
some of the action of histamine in the body are called as antihistamines.
• These drugs don not prevent the formation of histamine.
Antihistamine may be biologically classified as
1.
H1 blockers or H1 –Antagonist or classical
antihistamine
2. H2 blockers or H2 Antagonist
• H1 antagonist are useful for palliative (for reducing and cure)
treatment of allergic reactions like
• Seasonal
rhinitis
• Sneezing
• Nasal
discharge
• Itching of eyes,
nose, throats
• Hay fever
• H2 antagonists are mainly useful in the therapy of peptic ulcers as they
inhibit the local secretions and gastric secretions stimulated by gastrin.
Classical antihistamine (H1 blockers) can be chemically classified as follows
• Amino alkyl ethers: e.g. Diphenhydramine
• Ethylene diamine: Mepyramine
• Alkyl amines or propylamines
a) Saturated propylamines: e.g. Pheniramine,
Chloropheniramine.
b) Olefinic propylamines: e.g. Triprolidine
• Phenothizine derivatives: e.g. Promethazine.
• Piperazine derivatives: e.g. Meclozine
• Miscellaneous: e.g. Cyproheptadine
Histamine
Properties of Histamine:
• It is phosphate ester occurs as colourless,
• Long prismatic crystals
• It is odourless.
• It is freely soluble in water.
• It is slightly soluble in alcohol.
Stability and storage of Histamine:
• It is stable in air but affected by
light.
• Hence it is stored in tightly closed
light resistant containers.
Uses of Histamine:
• To treat the functional capacity of
gastric glands
• To dingoes pheochromocytoma
Dosage forms of Histamine: Histamine injections
Brand names of Histamine: Allergram, Cortanhist, Maridex
Diphenhydramine
Structure of Diphenhydramine:
Chemical name: 1-Dimethyl amino, 2-dimethyl methoxy ethane
Properties of Diphenhydramine:
• It is hydrochloride salt occurs as a white crystalline powder.
• It is odourless.
• It has bitter taste followed by sensation of numbness.
• It is freely soluble in water and chloroform.
• Very slightly soluble in ethers.
Stability and storage of Diphenhydramine:
• It is darken slowly when exposure to light.
• Hence it is stored in well closed light resistant containers.
Uses of Diphenhydramine:
• Allergic skin reactions like urticaria, purities.
• Seasonal rhinitis
• Vasomotor rhinitis
• Motion sickness and post operating vomiting
• Cardiac arrhythmia in combination with antazolin.
Dosage forms: Capsules, elixir
Brand names: Benadryl,
caladryl, Copex-D
Pheniramine
Properties of Pheniramine:
• It is official as melate salt.
• It is white crystalline powder.
• It has faint odour.
• It is soluble in water and alcohol.
• Slightly soluble in alcohol.
Stability and storage of Pheniramine:
• It is affected by air and light,
• Hence it is stored in tightly closed light resistant containers.
Uses: as under Diphenhydramine
Dosage forms: Pheniramine tablet.
Brand names:
Histol, Phenil, Diavil
Chlorpheniranine
Structure of Chlorpheniranine:
Chemical name: 3-(p-chlorophenyl),3-(pyrid
-2-yl) ,N,N-dimethyl propanamine
Properties of Chlorpheniranine:
• It is maleate salt which is white crystalline powder
• It is odourless
• It has bitter taste
• It is freely soluble in water
• Very slightly soluble in ether.
Uses: as under
pheniramine
Dosage forms: Elixir, Injection
Brand names: Corex, Zeet, Alergin, histacort
Mepyramine
Properties of Mepyramine:
• It is white or creamy, white crystalline powder.
• It has bitter taste
• It is very soluble in water.
• Freely soluble in alcohol.
Stability and storage: it is light sensitive and hence it is stored in well closed, light
resistant containers
Uses of Mepyramine:
• It is used to treat allergic and anaphylactic condition including hey
fever
• It has local anaesthetic and sedative action.
Dosage forms: Tablet, Injection, elixir
Brand names: Antihist, Kafal, Amthical
Promethazine
Properties of Promethazine:
• Its hydrochloride salt is white or faintly yellowish crystalline powder.
• It is odourless.
• It has bitter taste.
• It is very soluble in water.
• Freely soluble in alcohol.
Stability and storage of Promethazine:
• Promethazine hydrochloride is slowly discoloured when
exposed to light.
• Hence it is stored in well closed light resistant containers.
Uses of Promethazine:
• To treat non allergic skin condition like insects bite, urticaria.
• To treat insomnia.
• As a premedication where sedation is necessary.
• In motion sickness.
• In Parkinsonism
Cyproheptadine
Properties of Cyproheptadine:
• It is official as hydrochloride salt.
• It is white slightly yellowish
crystalline powder,
• It is odourless.
• It has slightly bitter taste.
• It is very slightly soluble in water.
• It is sparingly soluble in alcohol
• Soluble in chloroform.
Stability and storage: it is
stored in tightly closed containers.
Uses of Cyproheptadine:
• To treat non allergic skin condition like insects bite, urticaria.
• As appetite stimulant
• To treat anorexia nervosa
• To treat crushing's syndrome (pituitary
dependant).
• To treat migraine.
• It has Anticholinergics, sedative and
antialdosterone activity.
Pharmaceutical dosage forms:
Cyproheptadine tablets, Cyproheptadine Elixir
Brand names: Cyprid,
Peritol, Set up
UNIT-VI, Pharmacology, D. Pharm 2nd year pdf notes
In this Unit, we cover fallowing Topic…..
HISTAMINE AND ANTI-HISTAMINE
- Pharmacological actions
- Pharmacokinetics
- Classification
- Adverse effects
- Uses
Posts
0 Comments