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. Chlorpheniramine¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Chlorpheniramine binds to the histamine H1 receptor. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine. 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. Pyridoxine¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Vitamin B6 is the collective term for a group of three related compounds, pyridoxine (PN), pyridoxal (PL) and pyridoxamine (PM), and their phosphorylated derivatives, pyridoxine 5'-phosphate (PNP), pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP). Although all six of these compounds should technically be referred to as vitamin B6, the term vitamin B6 is commonly used interchangeably with just one of them, pyridoxine. Vitamin B6, principally in the form of the coenzyme pyridoxal 5'-phosphate, is involved in a wide range of biochemical reactions, including the metabolism of amino acids and glycogen, the synthesis of nucleic acids, hemogloblin, sphingomyelin and other sphingolipids, and the synthesis of the neurotransmitters serotonin, dopamine, norepinephrine and gamma-aminobutyric acid (GABA).
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. Chlorpheniramine¿¡ ´ëÇÑ Pharmacology Á¤º¸ In allergic reactions an allergen interacts with and cross-links surface IgE antibodies on mast cells and basophils. Once the mast cell-antibody-antigen complex is formed, a complex series of events occurs that eventually leads to cell-degranulation and the release of histamine (and other chemical mediators) from the mast cell or basophil. Once released, histamine can react with local or widespread tissues through histamine receptors. Histamine, acting on H1-receptors, produces pruritis, vasodilatation, hypotension, flushing, headache, tachycardia, and bronchoconstriction. Histamine also increases vascular permeability and potentiates pain. Chlorpheniramine, is a histamine H1 antagonist (or more correctly, an inverse histamine agonist) of the alkylamine class. It competes with histamine for the normal H1-receptor sites on effector cells of the gastrointestinal tract, blood vessels and respiratory tract. It provides effective, temporary relief of sneezing, watery and itchy eyes, and runny nose due to hay fever and other upper respiratory allergies. 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. Pyridoxine¿¡ ´ëÇÑ Pharmacology Á¤º¸ Vitamin B6 (pyridoxine) is a water-soluble vitamin used in the prophylaxis and treatment of vitamin B6 deficiency and peripheral neuropathy in those receiving isoniazid (isonicotinic acid hydrazide, INH). Vitamin B6 has been found to lower systolic and diastolic blood pressure in a small group of subjects with essential hypertension. Hypertension is another risk factor for atherosclerosis and coronary heart disease. Another study showed pyridoxine hydrochloride to inhibit ADP- or epinephrine-induced platelet aggregation and to lower total cholesterol levels and increase HDL-cholesterol levels, again in a small group of subjects. Vitamin B6, in the form of pyridoxal 5'-phosphate, was found to protect vascular endothelial cells in culture from injury by activated platelets. Endothelial injury and dysfunction are critical initiating events in the pathogenesis of atherosclerosis. Human studies have demonstrated that vitamin B6 deficiency affects cellular and humoral responses of the immune system. Vitamin B6 deficiency results in altered lymphocyte differentiation and maturation, reduced delayed-type hypersensitivity (DTH) responses, impaired antibody production, decreased lymphocyte proliferation and decreased interleukin (IL)-2 production, among other immunologic activities.
Caffeine¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ Low (25 to 36%). Chlorpheniramine¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ 72% Meclizine¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ Not Available Pyridoxine¿¡ ´ëÇÑ ´Ü¹é°áÇÕ Á¤º¸ 22%
Half-life
Caffeine¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ 3 to 7 hours in adults, 65 to 130 hours in neonates Chlorpheniramine¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ 21-27 hours Meclizine¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ 6 hours Pyridoxine¿¡ ´ëÇÑ ¹Ý°¨±â Á¤º¸ 15-20 days
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. Chlorpheniramine¿¡ ´ëÇÑ Absorption Á¤º¸ Well absorbed in the gastrointestinal tract. Meclizine¿¡ ´ëÇÑ Absorption Á¤º¸ Well absorbed Pyridoxine¿¡ ´ëÇÑ Absorption Á¤º¸ The B vitamins are readily absorbed from the gastrointestinal tract, except in malabsorption syndromes. Pyridoxine is absorbed mainly in the jejunum.
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). Chlorpheniramine¿¡ ´ëÇÑ Biotransformation Á¤º¸ Primarily hepatic via Cytochrome P450 (CYP450) enzymes.
Toxicity
Caffeine¿¡ ´ëÇÑ Toxicity Á¤º¸ LD50=127 mg/kg (orally in mice) Chlorpheniramine¿¡ ´ëÇÑ Toxicity Á¤º¸ LD50 = 306 mg/kg in humans, mild reproductive toxin to women of childbearing age. Meclizine¿¡ ´ëÇÑ Toxicity Á¤º¸ Symptoms of overdose include drowsiness and anticholinergic effects. LD50=mg/kg (orally in rat). Pyridoxine¿¡ ´ëÇÑ Toxicity Á¤º¸ Oral Rat LD50 = 4 gm/kg. Toxic effects include convulsions, dyspnea, hypermotility, diarrhea, ataxia and muscle weakness.
Drug Interactions
Caffeine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available Chlorpheniramine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Donepezil Possible antagonism of actionGalantamine Possible antagonism of actionRivastigmine Possible antagonism of actionEthotoin The antihistamine increases the effect of hydantoinFosphenytoin The antihistamine increases the effect of hydantoinMephenytoin The antihistamine increases the effect of hydantoinPhenytoin The antihistamine increases the effect of hydantoin Meclizine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Donepezil Possible antagonism of actionGalantamine Possible antagonism of actionRivastigmine Possible antagonism of action Pyridoxine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available
Chlorpheniramine¿¡ ´ëÇÑ Food Interaction Á¤º¸ Take with food.Avoid alcohol. Meclizine¿¡ ´ëÇÑ Food Interaction Á¤º¸ Take with food to reduce irritation. Avoid alcohol.
Caffeine¿¡ ´ëÇÑ Description Á¤º¸ A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine& Chlorpheniramine¿¡ ´ëÇÑ Description Á¤º¸ A histamine H1 antagonist used in allergic reactions, hay fever, rhinitis, urticaria, and asthma. It has also been used in veterinary applications. One of the most widely used of the classical antihistaminics, it generally causes less drowsiness and sedation than promethazine. [PubChem] 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] Pyridoxine¿¡ ´ëÇÑ Description Á¤º¸ The 4-methanol form of vitamin B 6 which is converted to pyridoxal phosphate which is a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, aminolevulinic acid. Although pyridoxine and Vitamin B 6 are still frequently used as synonyms, especially by medical researchers, this practice is erroneous and sometimes misleading (EE Snell; Ann NY Acad Sci, vol 585 pg 1, 1990). [PubChem]