Drugs which bind with the cholinergic receptors and lock the action of the Ach or Ach like drugs.
It is also called Anticholinergics.
Prototype is Atropine, obtained from natural plant source Atropa belladonna.
This drug was originally used by the women to dilate their pupils to look more beautiful.
Types—
Anti-muscarinic drugs—Atropine, Scopolamine (Datura stromontum), Tropicamide.
Anti-nicotinic drugs—skeletal muscle relaxants, ganglion blockers.
Classification of Anti-muscarinics—
1. Natural source—Atropine, Scopolamine
2. Semisynthetic—Homatropine
3. Synthetic—Ipratropium, Benztropine
Pharmacokinetics of anti-muscarinics—
Atropine and other tertiary drugs are widely distributed after absorption. Scopolamine is fully and rapidly distributed to the CNS. Atropine has half life of 2 hours. About 60% of the dose is excreted in the urine unchanged. Most of the rest appears as conjugates metabolites in the urine.
Anti-muscarinic drugs used in Ophthalmology—
Drug
Duration of action
Atropine
7-10 days
Homatropine
1-3 days
Cyclopentolate
2 day
Tropicamide
<1 day
Indication of use in eye conditions—
§ Accurate measurement of the refractive error, specially in onco-operative patients
§ To facilitate ophthalmological examination of the retina
§ To prevent Synechia (adhesion) formation in Uveitis and Iritis
Pharmacological effects of anti-muscarinic drugs—
On CNS—Atropine causes minimum stimulation, scopolamine causes drowsiness and amnesia. In toxic doses both may cause agitation and hallucination.
On respiratory system—Atropine blocks the muscarinic receptors in bronchial smooth muscle and glands thus producing bronchodilatation and ↓ bronchial secretion.
On GIT—these drugs block muscarinic receptors thuds reducing motility, salivary gland secretion and basal gastric HCl secretion.
On GUT—they block the muscarinic receptor of the urinary bladder and ureter and thus relaxing the bladder wall and shows voiding of urine.
On CVS—these drugs block vagal stimulation of heart (atrium) and cause relative tachycardia. Ventricles are less affected. The drugs cause vasodilatation of the blood vessels of the skeletal muscles by blocking muscarinic receptors.
On Eye—they block the muscarinic receptors of the pupillary constrictor muscle causing Mydriasis. Cycloplegia also occurs because of blocking of the muscarinic receptors of the ciliary body. It also prevents drainage of the aqueous humor and there is ↑ pressure so cannot be given in glaucoma.
Anti-muscarinic drugs used in GIT and GUT conditions—
Tertiary amines—Atropine, Scopolamine, Oxybutynine
Quaternary amines—Propantheline, Glycopyrrolate, Methoscopolamine
Uses—
1. To relief bladder spasm after prostate operation
2. To reduce urinary urgency in inflammatory bladder disease
3. To reduce incontinence, specially in elderly people
*** Ipratropium bromide is used in bronchial asthma.
*** Atropine destructs the ciliary process thus clearing of the bronchial secretion is hampered. So there is a chance of respiratory infection.
*** used for experimental purpose where cholinergic drugs are used, like eye disease –glaucoma, muscle disease –muscular weakness (Ach on the N-M junction can’t work)
*** esters can be used in bladder problem, enhancing the action of the smooth muscle of bladder,
*** tertiary alkaloids are lipid soluble, quaternary alkaloids are water soluble drugs.
Atropine—
Atropine is derived from Atropa belladonna.
It was used for cosmetic purpose for dilating the pupil during the period of renaissance.
Properties of Atropine—
o Tertiary amine compound
o Can cross the BBB
o Sufficiently lipid soluble to be absorbed from the gut and conjunctival sac
o It is a competitive antagonist of the muscarinic receptor
Indication of Atropine—
1. Treatment of OPC poisoning
2. Anti-parkinsonism
3. Anti-motion sickness
4. Premedication for anaesthesia
5. As antispasmodic
6. Infantile pyloric stenosis
Adverse effects of Atropine—
1. Dry mouth
2. Blurred vision
3. Hyperthermia
4. Muscle fasciculation
5. Constipation
6. Urinary retention
Contraindication of Atropine—
1. Acute congestive glaucoma
2. Congestive cardiac failure
3. Prostatic enlargement
4. Gastric outlet obstruction
It is also called Anticholinergics.
Prototype is Atropine, obtained from natural plant source Atropa belladonna.
This drug was originally used by the women to dilate their pupils to look more beautiful.
Types—
Anti-muscarinic drugs—Atropine, Scopolamine (Datura stromontum), Tropicamide.
Anti-nicotinic drugs—skeletal muscle relaxants, ganglion blockers.
Classification of Anti-muscarinics—
1. Natural source—Atropine, Scopolamine
2. Semisynthetic—Homatropine
3. Synthetic—Ipratropium, Benztropine
Pharmacokinetics of anti-muscarinics—
Atropine and other tertiary drugs are widely distributed after absorption. Scopolamine is fully and rapidly distributed to the CNS. Atropine has half life of 2 hours. About 60% of the dose is excreted in the urine unchanged. Most of the rest appears as conjugates metabolites in the urine.
Anti-muscarinic drugs used in Ophthalmology—
Drug
Duration of action
Atropine
7-10 days
Homatropine
1-3 days
Cyclopentolate
2 day
Tropicamide
<1 day
Indication of use in eye conditions—
§ Accurate measurement of the refractive error, specially in onco-operative patients
§ To facilitate ophthalmological examination of the retina
§ To prevent Synechia (adhesion) formation in Uveitis and Iritis
Pharmacological effects of anti-muscarinic drugs—
On CNS—Atropine causes minimum stimulation, scopolamine causes drowsiness and amnesia. In toxic doses both may cause agitation and hallucination.
On respiratory system—Atropine blocks the muscarinic receptors in bronchial smooth muscle and glands thus producing bronchodilatation and ↓ bronchial secretion.
On GIT—these drugs block muscarinic receptors thuds reducing motility, salivary gland secretion and basal gastric HCl secretion.
On GUT—they block the muscarinic receptor of the urinary bladder and ureter and thus relaxing the bladder wall and shows voiding of urine.
On CVS—these drugs block vagal stimulation of heart (atrium) and cause relative tachycardia. Ventricles are less affected. The drugs cause vasodilatation of the blood vessels of the skeletal muscles by blocking muscarinic receptors.
On Eye—they block the muscarinic receptors of the pupillary constrictor muscle causing Mydriasis. Cycloplegia also occurs because of blocking of the muscarinic receptors of the ciliary body. It also prevents drainage of the aqueous humor and there is ↑ pressure so cannot be given in glaucoma.
Anti-muscarinic drugs used in GIT and GUT conditions—
Tertiary amines—Atropine, Scopolamine, Oxybutynine
Quaternary amines—Propantheline, Glycopyrrolate, Methoscopolamine
Uses—
1. To relief bladder spasm after prostate operation
2. To reduce urinary urgency in inflammatory bladder disease
3. To reduce incontinence, specially in elderly people
*** Ipratropium bromide is used in bronchial asthma.
*** Atropine destructs the ciliary process thus clearing of the bronchial secretion is hampered. So there is a chance of respiratory infection.
*** used for experimental purpose where cholinergic drugs are used, like eye disease –glaucoma, muscle disease –muscular weakness (Ach on the N-M junction can’t work)
*** esters can be used in bladder problem, enhancing the action of the smooth muscle of bladder,
*** tertiary alkaloids are lipid soluble, quaternary alkaloids are water soluble drugs.
Atropine—
Atropine is derived from Atropa belladonna.
It was used for cosmetic purpose for dilating the pupil during the period of renaissance.
Properties of Atropine—
o Tertiary amine compound
o Can cross the BBB
o Sufficiently lipid soluble to be absorbed from the gut and conjunctival sac
o It is a competitive antagonist of the muscarinic receptor
Indication of Atropine—
1. Treatment of OPC poisoning
2. Anti-parkinsonism
3. Anti-motion sickness
4. Premedication for anaesthesia
5. As antispasmodic
6. Infantile pyloric stenosis
Adverse effects of Atropine—
1. Dry mouth
2. Blurred vision
3. Hyperthermia
4. Muscle fasciculation
5. Constipation
6. Urinary retention
Contraindication of Atropine—
1. Acute congestive glaucoma
2. Congestive cardiac failure
3. Prostatic enlargement
4. Gastric outlet obstruction
1 comment:
fabulous job , helped me a lot.
Post a Comment