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===Pathology===
===Pathology===
Following absorption from the gastrointestinal tract caffeine and theobromine are metabolised in the liver <ref name="multiples"> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>. Caffeine has a half life of 4.5 hours in dogs while theobromine has a half life of 17.5 hours <ref name="multiples"> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>. In humans the half life of theobromine ranges from 6 to 10 hours, significantly shorter than that in dogs which may explain the susceptibility of dogs to chocolate poisoning REF
Following absorption from the gastrointestinal tract caffeine and theobromine are metabolised in the liver <ref name="multiples"> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>. Caffeine has a half life of 4.5 hours in dogs while theobromine has a half life of 17.5 hours <ref name="multiples"> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>. In humans the half life of theobromine ranges from 6 to 10 hours, significantly shorter than that in dogs which may explain the susceptibility of dogs to chocolate poisoning REF.
Methylxanthines have the following modes of action.
*'''Antagonism of Adenosine Receptors:'''<ref name="multiples"> '''BSAVA Manual of Canine and Feline Emergency and Critical Care''' Second Edition, 2007</ref> this antagonism results in stimulation of the central nervous system, vasoconstriction and increase in heart rate <ref name="multiples">Tilley Smith'''The 5-Minute Veterinary Consult Canine and Feline''' (Third Edition), ''Lippincott, Williams and Wilkins'' </ref> and also diureses <ref name="multiples"> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>
*'''Antagonism of Adenosine Receptors:'''<ref name="multiples"> '''BSAVA Manual of Canine and Feline Emergency and Critical Care''' Second Edition, 2007</ref> this antagonism results in stimulation of the central nervous system and an increase in heart rate <ref name="multiples">Tilley Smith'''The 5-Minute Veterinary Consult Canine and Feline''' (Third Edition), ''Lippincott, Williams and Wilkins'' </ref> and also diureses <ref name="multiples"> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>
*'''Inhibition of Cyclic Nucleotide Phosphodiesterase:'''<ref name="multiple"> '''BSAVA Manual of Canine and Feline Emergency and Critical Care''' Second Edition,2007</ref> consequently there is an increase in cyclic AMP, which in turn leads to greater catecholamine release and their effects <ref name="multiples">Tilley Smith'''The 5-Minute Veterinary Consult Canine and Feline''' (Third Edition), ''Lippincott, Williams and Wilkins'' </ref>.
*'''Inhibition of Cyclic Nucleotide Phosphodiesterase:'''<ref name="multiple"> '''BSAVA Manual of Canine and Feline Emergency and Critical Care''' Second Edition,2007</ref> consequently there is an increase in cyclic AMP, which in turn leads to greater catecholamine release and their effects <ref name="multiples">Tilley Smith'''The 5-Minute Veterinary Consult Canine and Feline''' (Third Edition), ''Lippincott, Williams and Wilkins'' </ref>.
*'''Modulation of Intracellular Calcium Concentrations:'''Enhanced uptake and decreased sequestration within the cell leads to amplification of intracellular calcium levels in cardiac and skeletal muscle, the net result of which is a positive inotropic effect on these muscles. <ref name=multiples> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>.
*'''Modulation of Intracellular Calcium Concentrations:''' <ref name=multiples> '''http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm''', accessed on 04.10.2010 </ref>.
Ventricular fibrillation, and other cardiac dysrhythmias are most frequently the ultimate cause of death.<ref> Carson TL (2006) Methylxanthines. In: ''Small Animal Toxicology'', ed. ME Peterson, PA Talcott, pp.845-852. Elsevier Saunders, St. Louis in '''BSAVA Manual of Canine and Feline Emergency Care''' Chapter 19, Second Edition,2007 </ref>, <ref> Holmgren P, Norden-Petterson L and Ahlner J (2004)Caffeine fatalaties: four case reports. ''Forensic Science International'' '''139''', 71-73 '''BSAVA Manual of Canine and Feline Emergency Care''' Second Edition,2007 </ref>
Ventricular fibrillation, and other cardiac dysrhythmias are most frequently the ultimate cause of death.<ref> Carson TL (2006) Methylxanthines. In: ''Small Animal Toxicology'', ed. ME Peterson, PA Talcott, pp.845-852. Elsevier Saunders, St. Louis in '''BSAVA Manual of Canine and Feline Emergency Care''' Chapter 19, Second Edition,2007 </ref>, <ref> Holmgren P, Norden-Petterson L and Ahlner J (2004)Caffeine fatalaties: four case reports. ''Forensic Science International'' '''139''', 71-73 '''BSAVA Manual of Canine and Feline Emergency Care''' Second Edition,2007 </ref>