Antihistamines: Histamine receptors – H1- Allergic responses. Watery eyes, congestion, etc. from allergies. Anaphylaxis – bronchial larynx constriction. Skin allergic response – reddening, rashes, welts. Edema from injury. H2 – Gastric secretion. Important for ulcer treatment and acid reflux H3 – ? CNS receptors. There are also H1 receptors in the CNS. Antihistamines are also used for motion sickness. In general their antimuscarinic effects are similar to that of scopolamine, although weaker. Antihistamines


Histamine Agonists: Histamine Agonists


Antihistamines – H1 Blockers: Ethylenediamines Antihistamines – H1 Blockers


Antihistamine SAR: Aminoalkylethers Piperazine/N-heterocycle Series Antihistamine SAR


Stereo- and regioisomers: Antihistamines are stereospecific. A number of new, single isomer drugs are being developed. Antihistamines are structurally similar To SSRIs and to antipsychotics. Notice The subtle difference between fluoxetine And several antihistamines. Stereo- and regioisomers


Alkyl Amines: Alkyl Amines Long Duration, less sedation than ethylenediamines, ethanolamines. The “next best thing” until the “2nd generation” were developed.


Rigid Analogs (I): A Cl at the 2-position weakens H1 activity relative to antimuscarinic activity and D2 antagonist activity Rigid Analogs (I)


Rigid Analogs (II): Primethixene Loratadine (Claritin) Desloratadine (Clarinex) Rigid Analogs (II)


Astemizole: Hismanal was FDA approved in 1988 as an antihistamine for allergy and hay fever symptom relief. The FDA first warned consumers and healthcare providers of new safety information regarding Hismanal February 9, 1998 due to the risk of death, cardiovascular adverse events, anaphylaxis, and serious drug interactions. In addition, Hismanal labeling was changed to stress avoiding the use of Hismanal in combination with certain other medications and for liver disorder patients to completely avoid its' use. After a series of labeling changes and warnings Hismanal was recalled on June 21, 1999. Astemizole


Antihistamines “related” to butyrophenones: Terfenadine was discontinued when it became apparent that there was a high frequency of heart arrythmia associated with the drug. Fexofenadine is a metabolite and is the activated form responsible for antihistamine activity. In patients with compromised liver metabolism, or when the presence of other drugs limited the metabolism of terfenadine, persistent levels resulted in the observed arrythmias. Therefore, the fexofenadine replaced terfenadine (1997). Ventricular Arrythmias are not good! Antihistamines “related” to butyrophenones


Butyrophenone-like structures: Butyrophenone-like structures


Allegra Propaganda - www.allegra.com: Allegra Propaganda - www.allegra.com


www.zyrtec.com: If you haven't gotten the relief you want from Claritinｨ (loratadine), Clarinexｨ (desloratadine), or Allegraｨ (fexofenadine HCl), ask your doctor if ZYRTEC is right for you. www.zyrtec.com


Structural Summary: Linking the first generation with Non-sedative Antihistamines. Big Picture - Bottom Line Structural Summary


Anti-emetics: Anti-emetics


Anti-emetic Table: Synthetic Tropane Alkaloids Anti-emetic Table


2005 Nobel Prize: Press Release: The 2005 Nobel Prize in Physiology or Medicine 3 October 2005 The Nobel Assembly at Karolinska Institutet has today decided to award The Nobel Prize in Physiology or Medicine for 2005 jointly to Barry J. Marshall and J. Robin Warren for their discovery of "the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease” 2005 Nobel Prize


Gastric Secretions Cell Biology: Gastric Secretions Cell Biology


H2 Histamine antagonists.: Gastric receptors are pharmacologically distinct. The classic H1 antagonists don’t interact with H2 receptors. Antihistamines are an important treatment for gastric disorders; antacids, ulcer treatment, acid-reflux disease. H2 Histamine antagonists.


H2 Histamine antagonists. - Structures: H2 Histamine antagonists. - Structures