| Atropine Pharmacology |
| Atropine |
| About Atropine |
| Anti-cholinergic,Belladona alkaloid, Antidote ,Antispasmodic Agent,antiarrythmic,vagolytic , Mydriatic. |
| Mechanism of Action of Atropine |
| Atropine is an anticholinergic drug. It selectively inhibits the muscarinic receptors and antagonizes the muscarine like actions of Acetyl choline Atropine inhibits the muscarinic actions of acetylcholine on structures innervated by postganglionic cholinergic nerves, and on smooth muscles, which respond to endogenous acetylcholine. Atropine reduces secretions in the mouth and respiratory passages, relieves the constriction and spasm of the respiratory passages, and reduces the paralysis of respiration. Atropine-induced parasympathetic inhibition may be preceded by a transient phase of stimulation, especially on the heart where small doses first slow the rate before characteristic tachycardia develops due to paralysis of vagal control. Although mild vagal excitation occurs, the increased respiratory rate and occasionally increased depth of respiration produced by atropine are more probably the result of bronchiolar dilatation. Accordingly, atropine is an unreliable respiratory stimulant and large or repeated doses may depress respiration. Adequate doses of atropine abolish various types of reflex vagal cardiac slowing or asystole. The drug also prevents or abolishes Bradycardia or asystole produced by injection of choline esters, anticholinesterase agents or other parasympathomimetic drugs, and cardiac arrest produced by stimulation of the vagus. Atropine may also lessen the degree of partial heart block when vagal activity is an etiologic factor. In some individuals with complete heart block, the idioventricular rate may be accelerated by atropine; in others, the rate is stabilized. Occasionally, a large dose may cause atrio ventricular (A-V) block and nodal rhythm. Atropine in clinical doses counteracts the peripheral dilatation and abrupt decrease in blood pressure produced by choline esters. However, when given by itself, atropine does not exert a striking or uniform effect on blood vessels or blood pressure. Systemic doses slightly raise systolic and lower diastolic pressures and can produce significant postural hypotension. Such doses also slightly increase cardiac output and decrease central venous pressure. Occasionally, therapeutic doses dilate cutaneous blood vessels, particularly in the “blush” area (atropine flush), and may case atropine “fever” due to suppression of sweat gland activity especially in infants and small General anaesthesia: Once muscle paralysis is no longer desired, acetyl cholinesterase inhibitors are combined with a muscarinic receptor antagonist such as Glycopyrrolate or Hyoscine or Atropine to offset the muscarinic activation resulting from esterase inhibition |
| Pharmacokinets of Atropine |
| Absorption: Atropine is well absorbed after parenteral administration. Distribution: It is widely distributed in the body and it crosses the blood brain barrier Metabolism: Atropine undergoes metabolism in the liver. Excretion: It is excreted mainly in the urine and small amount may be excreted in faeces and in expired air. |
| Onset of Action for Atropine |
| IM: 5 – 40 minutes |
| Duration of Action for Atropine |
| IM: 4 hours |
| Half Life of Atropine |
| 12 hours |
| Side Effects of Atropine |
| 1. Dry mouth 2.Constipation 3.Difficulty in swallowing 4.Tachycardia 5.Headache 6.Restlessness 7.Insomnia 8.Dizziness 9.Nausea 10.Vomiting 11.Decreased secretions 12.Irritation at the site of injection site 13.Fever 14.Retention of urine |
| Contra-indications of Atropine |
| 1.Hypersensitivity to Atropine and other belladonna alkaloids 2.Tachycardia 3.Obstructive disease of gastrointestinal tract 4.Obstructive uropathy 5.Unstable cardiovascular status in acute haemorrhage 7.Paralytic ileus 8.Toxic megacolon 9.Intestinal atony 10.Asthma 11.Myasthenia gravis 12.Thyrotoxicosis |
| Special Precautions while taking Atropine |
| 1.Any work that require mental alertness like drivingoperating machineAlcoholics |
| Pregnancy Related Information |
| Contraindicated |
| Old Age Related Information |
| Use with caution |
| Breast Feeding Related Information |
| Use with caution |
| Children Related Information |
| Use with caution |
| Indications for Atropine |
| 1. Pre anaesthetic medication 2. Symptomatic Bradycardia 3.To block the adverse muscarinic effect of anticholinesterase agents 4.Antidote for anticholinesterase insecticide poisoning 5.Bronchospasm 6.Cycloplegic refractions 7.Acute iritis 8.Lessen the degree of AV block |
| Interactions for Atropine |
| N/A |
| Typical Dosage for Atropine |
| Parenteral Adult: Pre anaesthetic medication: (IM) or (SC) 300-600mcg is given 30-60 minutes before surgery. Bradycardia (IV ): 0.3 – 1 mg dose can be repeated every 3 – 5 minutes 0.03 mg / kg in patient with mild Bradycardia and 0.4 mg / kg with severe Bradycardia, To block the adverse muscarinic effect of anticholinesterase agents: 0.6 – 1.2 mg for each 0.5 – 2.5 mg of Neostigmine administered intravenously a few minutes before anticholinesterase agents. Antidote for anticholinesterase insecticidal poisoning: (IM or IV): Initial dose: 1 – 2mg is given and dose can be increased up to 6 mg in severe cases and repeat the dose every 5 – 60 minutes until muscarinic symptoms disappears. Prevention of Bronchospasm: 0.025 mg / kg is administered with the help of a nebulisers 3 – 4 times daily up to 2.5 mg Children Premedication: (IM) or (SC): 20mcg/kg. Bradycardia (IV): 10 – 20 mcg/kg doses can be repeated up to 1 mg Antidote for anticholinesterase insecticidal poisoning: (IM or IV): Initial dose: 0.05 mg / kg is given and repeat the dose every 10 -30 minutes until muscarinic symptoms disappears |
| Schedule of Atropine |
| H |
| Storage Requirements for Atropine |
| Store at 15 – 30 degree C. Protect from light. Keep out of the reach of children |
| Effects of Missed Dosage of Atropine |
| N/A |
| Effects of Overdose of Atropine |
| Give supportive measures and symptomatic treatment. Physostigmine can be given to reverse the excessive anticholinergic activity produced by Atropine. |