Drug presentation 1 agonist/antagonist Barry Barkinsky EMS-I, Paramedic

Receptor sites.. Drugs either stimulate or inhibit the cells normal biochemical actions

Receptor sites Point of attachment for hormones, viruses, chemicals

Agonist / antagonist

Lock and key analogy Agonist works like a lock and key that works

Agonists Bind to the receptor site and initiate the expected response If you put the key in the lock and turn it the lock will open Side effect

Morphine sulfate class: opioid agonist Prototype drug : –Causes analgesia, euphoria, sedation and miosis. – Decreases preload and afterload. –May cause respiratory depression and hypotension.

Morphine…mechanism Opiate agonist Cause the desired effect of pain relief Also opens doors to respiratory depression and hypotension Has successfully opened doors to: –Pain relief / High –Respiratory depression –Hypotension via vasodilation

Morphine sulfate Indications –Moderate to severe pain –Cardiac pain indicative of MI –Acute pulmonary edema Precautions: –Hypersensitivity, undiagnosed head or abdomen injury, bronchial asthma, COPD, severe respiratory depression, pulmonary edema due to chemical agent

Fentanyl (sublimaze) potency many times that of morphine. Schedule II drug Also seen as duragesic or actiq High potential for respiratory depression Anesthetic and analgesic – dose dependant

Fentanyl (sublimaze) synthetic narcotic analgesic Indications: Induce sedation for endotracheal intubation. Contraindications: MAO inhibitors within 14 days, myasthenia gravis. Precautions: Increased intracranial pressure, elderly, debilitated, COPD, respiratory problems, hepatic and renal insufficiency. Dosage/Route: 25 to 100 mcg slowly IV (2 to 3 min). Ped: 2 mcg/kg slow IV/IM.

Stadol

Noncompetitive antagonism The antagonism is insurmountable Example: You can’t effectively push CO off of hemoglobin once its got the site

Competitive antagonism Considered surmountable Enough of an agonist can overcome the antagonism

Competitive Antagonists Bind to the site but do not cause the receptor to initiate the expected response The key fits in the lock but will not turn and cannot open the lock – however the lock is now blocked

Opioid antagonists Reverse some of the effects of opioid drugs Typically desired for respiratory depression effect Shorter half life than most opioid drugs

Reversal Naloxone: opiate antagonist –Binds to opiate receptor – fits in lock but doesn’t turn it – blocks it Doesn’t elicit the desired response: –No pain relief / No high– door blocked –No respiratory depression – door blocked –Can’t bind to the receptor causing vasodilation morphine has bound to – so hypotension is not reversed – door NOT blocked Morphine-----  >>>> Pain relief / High Respiratory depression Hypotension

Naloxone (narcan) Prototype opioid antagonist drug Repeat doses may be needed to combat shorter half life Competitively binds with opioid receptors without causing the effects of opioid binding. Primary binding is at respiratory centers – it will not reverse hypotension

narcan Indication: –Natural of synthetic narcotic overdose –Coma of unknown origin Precaution: shorter half life than most of the drugs it antagonizes Dosage/Route: 0.4 to 2.0 mg IV/IM, 2 to 2.5X ET up to 10 mg, 2 mg MAD