Caffeine¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Caffeine stimulates medullary, vagal, vasomotor, and respiratory centers, promoting bradycardia, vasoconstriction, and increased respiratory rate. This action was previously believed to be due primarily to increased intracellular cyclic 3¡Ç,5¡Ç-adenosine monophosphate (cyclic AMP) following inhibition of phosphodiesterase, the enzyme that degrades cyclic AMP. It is now thought that xanthines such as caffeine act as agonists at adenosine-receptors within the plasma membrane of virtually every cell. As adenosine acts as an autocoid, inhibiting the release of neurotransmitters from presynaptic sites but augmenting the actions of norepinephrine or angiotensin, antagonism of adenosine receptors promotes neurotransmitter release. This explains the stimulatory effects of caffeine. Blockade of the adenosine A1 receptor in the heart leads to the accelerated, pronounced "pounding" of the heart upon caffeine intake. Meclizine¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Along with its actions as an antagonist at H1-receptors, meclizine also possesses anticholinergic, central nervous system depressant, and local anesthetic effects. Meclizine depresses labyrinth excitability and vestibular stimulation and may affect the medullary chemoreceptor trigger zone. Scopolamine¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Scopolamine acts by interfering with the transmission of nerve impulses by acetylcholine in the parasympathetic nervous system (specifically the vomiting center).
Pharmacology
Caffeine¿¡ ´ëÇÑ Pharmacology Á¤º¸ Caffeine, a naturally occurring xanthine derivative like theobromine and the bronchodilator theophylline, is used as a CNS stimulant, mild diuretic, and respiratory stimulant (in neonates with apnea of prematurity). Often combined with analgesics or with ergot alkaloids, caffeine is used to treat migraine and other headache types. Over the counter, caffeine is available to treat drowsiness or mild water-weight gain. Meclizine¿¡ ´ëÇÑ Pharmacology Á¤º¸ Meclizine, a piperazine-derivative H1-receptor antagonist similar to buclizine, cyclizine, and hydroxyzine, is used as an antivertigo/antiemetic agent. Meclizine is used in the management of nausea, vomiting, and dizziness associated with motion sickness and vertigo in diseases affecting the vestibular apparatus. Scopolamine¿¡ ´ëÇÑ Pharmacology Á¤º¸ Scopolamine is a muscarinic antagonist structurally similar to the neurotransmitter acetylcholine and acts by blocking the muscarinic acetylcholine receptors and is thus classified as an anticholinergic. Scopolamine has many uses including the prevention of motion sickness. It is not clear how Scopolamine prevents nausea and vomiting due to motion sickness. The vestibular part of the ear is very important for balance. When a person becomes disoriented due to motion, the vestibule sends a signal through nerves to the vomiting center in the brain, and vomiting occurs. Acetylcholine is a chemical that nerves use to transmit messages to each other. It is believe that Scopolamine prevents communication between the nerves of the vestibule and the vomiting center in the brain by blocking the action of acetylcholine. Scopolamine also may work directly on the vomiting center. Scopolamine must be taken before the onset of motion sickness to be effective.
Metabolism
Caffeine¿¡ ´ëÇÑ Metabolism Á¤º¸ # Phase_1_Metabolizing_Enzyme:Cytochrome P450 1A2 (CYP1A2) Meclizine¿¡ ´ëÇÑ Metabolism Á¤º¸ # Phase_1_Metabolizing_Enzyme:Monoamine oxidase type B (MAO-B) Scopolamine¿¡ ´ëÇÑ Metabolism Á¤º¸ # Phase_1_Metabolizing_Enzyme:Not Available
Protein Binding
Caffeine¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ Low (25 to 36%). Meclizine¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ Not Available Scopolamine¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ Not Available
Half-life
Caffeine¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ 3 to 7 hours in adults, 65 to 130 hours in neonates Meclizine¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ 6 hours Scopolamine¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ Not Available
Absorption
Caffeine¿¡ ´ëÇÑ Absorption Á¤º¸ Readily absorbed after oral or parenteral administration. The peak plasma level for caffeine range from 6-10mg/L and the mean time to reach peak concentration ranged from 30 minutes to 2 hours. Meclizine¿¡ ´ëÇÑ Absorption Á¤º¸ Well absorbed Scopolamine¿¡ ´ëÇÑ Absorption Á¤º¸ Not Available
Caffeine¿¡ ´ëÇÑ Biotransformation Á¤º¸ Hepatic cytochrome P450 1A2 (CYP 1A2) is involved in caffeine biotransformation. About 80% of a dose of caffeine is metabolized to paraxanthine (1,7-dimethylxanthine), 10% to theobromine (3,7-dimethylxanthine), and 4% to theophylline (1,3-dimethylxanthine). Scopolamine¿¡ ´ëÇÑ Biotransformation Á¤º¸ Not Available
Toxicity
Caffeine¿¡ ´ëÇÑ Toxicity Á¤º¸ LD50=127 mg/kg (orally in mice) Meclizine¿¡ ´ëÇÑ Toxicity Á¤º¸ Symptoms of overdose include drowsiness and anticholinergic effects. LD50=mg/kg (orally in rat). Scopolamine¿¡ ´ëÇÑ Toxicity Á¤º¸ Not Available
Drug Interactions
Caffeine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available Meclizine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Donepezil Possible antagonism of actionGalantamine Possible antagonism of actionRivastigmine Possible antagonism of action Scopolamine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available
Caffeine¿¡ ´ëÇÑ Description Á¤º¸ A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine& Meclizine¿¡ ´ëÇÑ Description Á¤º¸ A histamine H1 antagonist used in the treatment of motion sickness, vertigo, and nausea during pregnancy and radiation sickness. [PubChem] Scopolamine¿¡ ´ëÇÑ Description Á¤º¸ An alkaloid from Solanaceae, especially Datura metel L. and Scopola carniolica. Scopolamine and its quaternary derivatives act as antimuscarinics like atropine, but may have more central nervous system effects. Among the many uses are as an anesthetic premedication, in urinary incontinence, in motion sickness, as an antispasmodic, and as a mydriatic and cycloplegic. [PubChem]