Lecture 34/35 Flashcards
Antimuscarinic
Chol. Acute Symptoms
-Cholinergic direct and indirect agonist: DUMBELS & 3 Bs
Anticholinergic Symptoms
Opposite of DUMBELS
DUMBELS + 3 Bs
D - Diarrhea ==> Constipation (Dicyclomine, bowel syndromes)
U - Urinary Frequency ==> Urinary retention (Oxybutynin, Tolterodine)
M - Miosis ==> Mydriasis (Tropicamide, dilate pupil)
B - Bradycardia ==> Tachycardia (Atropine, AtroPEN)
Bronochorrhea ==> Decreased lung secretions (COPD, Asthma)
Bronchoconstriction ==> Bronchodilation (Ipratropium, Tiotropium)
E - Emesis ==> Less GI effects (help in treatment of bowel syndromes)
L - Lacrimation ==> Dry eyes (side effect)
S - Salivation ==> Dry mouth (side effect)
Anticholinergic CNS Uses
- Parkinson’s and Antipsychotic drugs (Benztropine)
- Motion sickness (Scopolamine)
- Deter drug abuse (Atropine)
Cholinergic Antagonists
- AKA Anticholinergics
- Bind to ACh-esterase, does NOT trigger receptor effect
- Prevents cholinergic drug binding
- Muscarinic antagonists, ganglionic blockers, and neuromuscular blockers are all examples
Muscarinic Antagonists
- Wise therapeutic use
- Selectively blocks muscarinic synapses of parasympathetic NS and CNS
- Tissues innervated by both sym. and parasym. will show increased sym. NS activity
Ganglionic Blockers
- Antagonizes nicotinic receptors on symp. and parasymp. ganglion
- Few clinical uses
Neuromuscular Blockers
- Block ACh effects on skeletal muscles
- Muscle relaxants, intubation agents, and surgery uses
Atropine Origin
- Prototype muscarinic antagonist
- Tertiary amine from Atropa belladonna
- Increase pupil size and rosy cheeks
- All parts of the plant are poisonous
- Anticholinergic compounds in Belladonna: Atropine (d, l-hyoscamine) and Scopolamine (hyoscine)
Antimuscarinic Agents
- Atropine
- Scopolamine
- Ipratropium
- Cyclopentolate
- Tropicamide
Long-Acting
- Tiotropium
- Aclindium
Jimson Weed
- Potentially abused by teens and adolescents
- Active ingredients: Atropine and Scopolamine
- Benefits: treats cough, asthma, intestinal cramps, diarrhea, bedwetting
- Side effects: Mydriasis, hallucinogen, delirium, anticholinergic crisis, death
Types of Muscarinic Receptor Antagonist
- Naturally occurring alkaloids; Atropine and Scopolamine
- Semisynthetic - derivatives of alkaloids, differ from parent by body disposition or duration of action. Examples: Homatropine and Tropicamide (Mydriacyl) - shorter duration; Ipratropium, Tiotropium, Aclindinium - Quaternary amines and don’t cross BBB
- Synthetic compounds, some selectivity for subtypes of muscarinic receptors. Examples: Pirenzepine - treat GI ulcers in some countries; Tolterodine, Oxybutynin, and other - urinary incontinence
Selectivity of Muscarinic Receptor Antagonist
- Little or no blockage at nicotinic receptor sites
- Parasympathetic muscarinic receptors in different organs vary in their sensitivity to muscarinic receptor antagonist
Atropine + Doses
- Low doses - depresses salivation/bronchial secretions and sweating
- Moderate doses - pupil dilates, heart rate increases, accommodation for vision (far vision)
- Large doses - Antagonize bladder, GI control, inhibits peeing an decreases motility/tone of gut (constipation)
- Highest dose - greater inhibition of gastric motility/secretion
Atropine Doses + Effects
- Doses of Atropine and most related muscarinic receptor antagonists that decrease gastric motility and secretion ALSO affect:
1. Salivary secretion (Dry mouth)
2. Ocular accommodation (blurred vision)
3. Micturition (difference in urination)
4. GI tone (constipation)
5. Heart rate (especially unopposed sympathetic)
Differences in sensitivities NOT due to differing affinities of muscarinic receptors since Atropine is NOT selective to muscarinic subtypes. More likely due to degree that various organ are regulated by parasympathetic tone.
Muscarinic Antagonists affect following tissues:
- CNS
- Eye
- CV System
- Circulatory
- Respiratory Tract
- GI Tract
- Urinary Tract
CNS Antimuscarinics
- Atropine: clinical doses have little effects, high doses cause CNS excitation (hallucinations, delirium) and eventual depression which can result in cardiac and respiratory failure
- Scopolamine: clinical doses - CNS depression with drowsiness, amnesia, fatigue
CNS Therapeutic Uses
- Benztropine (Cogentin, Trihexyphenidyl (Artane)
- Help correct imbalance of too little dopamine and excess ACh (Parkinsons, after antipsychotic treatment)
- Side effects: Antichol. in PNS, confusion, memory problems
Scopolamine Therapeutic Uses
- 1 mg patch/3 days
- Prevents N/V from:
1. Motion sickness - apply to hairless area behind ear 4 hours before needed effect
2. Recovering from anesthesia and surgery - apply patch evening before surgery
Scopolamine Side Effects/Warning
-Dry mouth (66%)
-Drowsiness (16%)
WARNING: Chronic open-angle glaucoma patients should be monitored since mydriatic effect could increase IOP
Eye Antimuscarinics
- Tropicamide (Mydriacyl)
- Blocks cholinergic effect on papillary sphincter muscles of iris which:
1. Dilates pupil producing mydriasis
2. Paralyzes ciliary muscles - near objects are blurred (cycloplegia)
3. Abolishes normal papillary reflex constriction to light
Tropicamide Therapeutic Uses
- Examination of retina and optic disc
2. Decrease in painful ciliary muscle spasm
Tropicamide Side Effects
- Photophobia - intolerance of bright light
- Transient stinging and slight increase in IOP
- Rare: causes an attack of acute angle-closure glaucoma
Accomodation
Process by which eye changes focus to see objects at various distances
-Antimus. limits focusing to distant objects