目前分類:Pharmacology (5)

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  • Nov 27 Thu 2008 22:23
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Medicon
Vena
Victaril  before Vancomycin

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Epinephrine (also referred to as adrenaline; see Terminology) is a hormone and neurotransmitter. It is a catecholamine, a sympathomimetic monoamine derived from the amino acids phenylalanine and tyrosine. The Latin roots ad-+renes and the Greek roots epi-+nephros both literally mean "on/to the kidney" (referring to the adrenal gland, which sits atop the kidneys and secretes epinephrine). Epinephrine is often shortened to epi or to EP in American medical jargon.

Mechanism of action

Epinephrine's actions are mediated through adrenergic receptors. Epinephrine is a non-selective agonist of all adrenergic receptors. It activates α1, α2, β1, and β2 receptors.[6] Specific functions include:

  • It binds to α1 receptors of liver cells, which activate inositol-phospholipid signaling pathway, signaling the phosphorylation of glycogen synthase and phosphorylase kinase (inactivating and activating them, respectively), leading to the latter activating another enzyme—glycogen phosphorylase—which catalises breakdown of glycogen (glycogenolysis) so as to release glucose to the bloodstream. Simultaneously protein phosphatase-1 (PP1) is inactivated, as in the active state PP1 would reverse all the previous phosphorylations.
  • Epinephrine also activates β-adrenergic receptors of the liver and muscle cells, thereby activating the adenylate cyclase signaling pathway, which will in turn increase glycogenolysis.

β2 receptors are found primarily in skeletal muscle blood vessels where they trigger vasodilation. However, α-adrenergic receptors are found in most smooth muscles and splanchnic vessels, and epinephrine triggers vasoconstriction in those vessels.


 

治療Horner's syndrome

 

Definition of Horner syndrome

 Horner syndrome: A complex of abnormal findings, namely sinking(下沉) in of one eyeball, ipsilateral ptosis (drooping of the upper eyelid on the same side) and miosis (constriction of the pupil of that eye) together with anhidrosis (lack of sweating) and flushing of the affected side of the face. Due to paralysis of certain nerves (specifically, the cervical sympathetic nerves). Also called Horner-Bernard syndrome, Bernard syndrome, Bernard-Horner syndrome and Horner's ptosis (but best known as Horner syndrome).

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Pilocarpine is a muscarinic alkaloid obtained from the leaves of tropical American shrubs from the genus Pilocarpus. It is a non-selective muscarinic receptor agonist[1] in the parasympathetic nervous system, which acts therapeutically at the muscarinic acetylcholine receptor M3 due to its topical application[2], e.g. in glaucoma and xerostomia.

causing miosis

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Ergotamine is an ergopeptine and part of the ergot family of alkaloids; it is structurally and biochemically closely related to ergoline. It possesses structural similarity to several neurotransmitters, and has biological activity as a vasoconstrictor. It is used medicinally for treatment of acute migraine attacks (sometimes in combination with caffeine), and to induce childbirth and prevent post-partum haemorrhage. It was first isolated from the ergot fungus by Arthur Stoll at Sandoz in 1918 and marketed as Gynergen in 1921. [1]

Mechanism of action

The mechanism of action of ergotamine is complex.[2] The molecule shares similarity with neurotransmitters such as serotonin, dopamine, and adrenaline and can thus bind to several cell receptors acting both as agonist and antagonist in signal transduction within cellular tissues. The anti-migraine effect is due to constriction of the intercranial extracerebral blood vessels through the 5-HT1B receptor, and by inhibiting trigeminal neurotransmission by 5-HT1D receptors. Ergotamine also has effects on the dopamine and noradrenaline receptors. It is its action on the D2 dopamine and 5-HT1A receptors that can cause some side effects. [3]

Drug uses

Ergotamine is also a precursor of LSD, lysergic acid diethylamide. It produces vasoconstriction peripherally. It damages the peripheral epithelium and in high doses is conducive to the creation of vascular stasis, thrombosis and gangrene. It can increase uterine contractivity and has, in the past, been used therapeutically in the immediate post-partum state. It continues to be prescribed for migraine. Contraindications include: atherosclerosis, Buerger's syndrome, coronary artery disease, hepatic disease, pregnancy, pruritus, Raynaud's syndrome, and renal disease. [5]

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