Autacoids are locally acting substances that are synthesized in tissues and have physiological and pathological effects at the site of synthesis. They have brief actions as they are destroyed locally, earning them the name "local hormones". Autacoids include histamine, serotonin, angiotensin, kinins, prostaglandins, leukotrienes, and platelet activating factor. Histamine is a biogenic amine found in many tissues and also bee and wasp venom, acting as a mediator of inflammatory responses. Antihistamines are classified as sedating or non-sedating and are used to treat conditions caused by histamine such as allergic reactions and inflammation.

1. Autacoids
• Autacoids are substances formed in varioustissues,
have complex physiologic andpathologic actions
and act locally at the siteof synthesis.
• They have a brief action andare destroyed locally.
Hence they are called‘local hormones’ and differ
from truehormones.
• . The word autacoid is derived from Greek: autos =
self akos = remedy

2. Autacoids Include
• Histamine,
• 5-hydroxytryptamine
• Angiotensin,
• kinins,
• Prostaglandins,
• leukotrienes,
• platelet activating factor.

4. HISTAMINE
Histamine or tissue amine (Histos = tissue) is
a biogenic amine formed in many tissues. It
is also found in the venoms of bees, wasps
and other stinging secretions.

7. Antihistamines,

8. Classification
• Di-phen-hydra-mine, (20-50 mg oral,IM.,)
• Pro-metha-zine (20-25 mg oral, IM )
1. Sedative
2. Non - sedative
• Phenira-mine(25-50 mg oral, IM )
• Chlor-phenira-mine ( 4-20 mg oral, IM )
• Cycli-zine (50 mg oral)
3.newer non sedative ( 2nd generation agent)
• Citrizine(10mg oral)
• Tera-fena-dine
• Fexo-fena-dine