Lecture 4: Anticholinergic drugs Lecturer Cristina GHICIUC, MD, PhD 1 Lecture 4: CHOLINERGIC SYSTEM (Parasympathetic Nervous System) AND DRUGS ANTICHOLINERGIC DRUGS (PARASYMPATHOLYTICS = Cholinolytics = Cholinoceptor-blocking drugs = Cholinoceptor antagonists) are divided on the basis of their specific receptor affinities into: muscarinic antagonists (Muscarinic Receptor Antagonist = Atropinic Drugs = mucarinic receptor-blocking drugs = ANTIMUSCARINICS); nicotinic antagonists (antagonists of nicotinic receptors or nicotinic receptor-blocking drugs), which are divided into: antagonists of Nn receptors (ganglionic blockers = GANGLIOPLEGICS);antagonists of Nm receptors (NEUROMUSCULAR BLOCKING DRUGS = skeletal muscle relaxants = curare like substances).Anticholinergic drugs are called parasympatholytic or cholinolytics because they block the effects of parasympathetic autonomic system.Lecture 4: Anticholinergic drugs Lecturer Cristina GHICIUC, MD, PhD 2 I. (muscarinic antagonists) have some effects that are not predictable from block of the parasympathetic nervous system.
Atropine (Hyoscyamine) is found in the plant Atropa belladonna (deadly nightshade) and in Datura stramonium (known as jimsonweed or Jamestown weed or sacred Datura, or thorn apple), Scopolamine (Hyoscine) is found in the plant Hyoscyamus niger, or henbane.Classification 1.Natural antimuscarinic drugs:
- Atropine (Hyoscyamine),
- Scopolamine (Hyoscine).2.Semisynthetic and synthetic derivatives:
Antimuscarinic drugs used in gastrointestinal and genitourinary disorders- antispasmodics (reduce tone and motility of gastrointestinal and genitourinary smooth muscle):
Centrally acting skeletal muscle relaxants (used to treat acute local skeletal muscle spasm): Chlorzoxazone, Orphenadrine, Cyclobenzaprine, Carisoprodol, Chlorphenesin, Metaxolone, Methocarbamol 2.7.Drugs used to treat acute local skeletal muscle spasm and generalized spastic disorders: botulinum toxin type A and B.
Atropine causes reversible blockade of cholinomimetic actions at muscarinic receptors.Atropine has high affinity for muscarinic receptors and it is not selective on muscarinic receptors (does not distinguish between subgroups of muscarinic receptors).
This mechanism explains the use as antidote in organophosphate intoxication or muscarine intoxication.
This mechanism explains the use in small doses as adjuncts to treatment of myasthenia gravis.Pharmacodynamic effects
- Heart: tachycardia by blocking vagal effects on M receptors on the SA nodal pacemaker (there is an initial bradycardia before the effects of peripheral vagal block become manifest).
This effect is useful in the treatment of bradicardia, asystolia.This effect explains tachycardia as adverse effects and the contraindication in coronary atherosclerosis and in tachycardia (hyperthyroidism, cardiac insufficiency).
- Blood vessels: at toxic doses, and in some individuals at normal doses, antimuscarinic agents cause cutaneous vasodilation, especially in the upper portion of the body.The mechanism is unknown.
There is little effect on blood pressure.2.Smooth muscle (gastro-intestinal, genito-urinary, bronchial): - antispasmodic agents (decrease the normal tone and amplitude of contractions) - this effect usually is not sufficient to overcome or prevent the marked spasm.Intestinal "paralysis" induced by antimuscarinic drugs is temporary; local mechanisms within the enteric nervous system will usually reestablish at least some peristalsis after 13 days of antimuscarinic drug therapy.
This action is useful in the treatment of intestinal hypertonicity and hypermotility, of the spasm of biliary and uretered colic.
Alternative drugs from synthetic compounds are , Dicyclomine,Mebeverine.This effect explains constipation as adverse effects (this effect is temporary
maximum 3 days).- increase the normal tone of sphincters This effect is useful in the treatment of urinary incontinence, but for this indication are prefered synthetic derivatives such as Trospium, Emepronium, Oxybutynin, Tolterodine, Propiverine, Darifenacin, Solifenacin.This effect explains acute urinary retention as adverse effects and the contraindication in prostatic hyperplasia.- bronchodilation in persons with asthma.This effect is useful as adjuncts to treatment of recent bronchial asthma and for chronic obstructive pulmonary disease.
For this indication are prefered synthetic derivatives such as Ipratropium, Oxitropium, Tiotropium.3
- cycloplegia (or paralyze the ciliary muscle):results in loss of the ability to accommodate, so eye cannot focus for near vision.
- mydriasis (pupillary
Binocular Vision Disorders for the Primary Care OD: How to Do it Fast and Get it Right firstname.lastname@example.org
2 2 indirect: flippers, MEM retinoscopy, NRA/PRAvergence facility: 12BO/3BIConvergence amplitudenear point of convergence (NPC)different targets, penlight and red lens most sensitive testSensory staWorth 4stereopsis2.Evaluation of accommodative statusaccommodative amplitude: push up vs.pull awayaccommodative facility: binocular and monocular +2.00/2.00 flippersaccommodative response: MEM retinoscopy, fused xcylinderC.Minimum DataBase for Children and Symptomatic Adults4 TestsCover test/phoriaNPCVergences+2.00/2.00 flippers, monocular vs.
Binocular and Accommodative Disorders1.Case history: 4 basic questionsDo your eyes bother you during reading? (blur, double, fatigue, eyestrain or loss of place?) Do you get a lot of headaches?Do you like to read?Any learning or reading problems in school?2.Signs and symptoms of binocular and accommodative problemseyestrain or fatigue during reading or deskworkheadaches associated with near worknear blur or blur when changing fixationintermittent diplopia, words moving or running togetherblinking, tearing, redness, squinting, rubbingpoor attention and concentration with reading and homeworklearning problemsclose working distanceclosing or covering one eyeloss of place, slow reading speed, uses finger to readpoor reading comprehension, avoids readinghead tilt or face turn3..
Questions to rule out nonfunctional problemsonset ofsymptoms?recent illness or trauma? medication?change in appetite or sleep?dizziness? balance problems? fainting spells?headaches? location, frequency, onset, duration, severity, time of day
3 3 associated with visual tasksmuscle weakness? numbness or tingling sensations?.
Minimum data base to rule out nonfunctional problemsexternal evaluationpupil evaluation including swinging flashlight testcolor visionophthalmoscopyversions/ comitancycover test at distance and near, nine positions of gazeconfrontation visual fields or neurological screening field.
Whats the Problem?a.
Compare results to expected findingsb.Group the findings that differ from expectedpositive fusional vergence (PFV) group: BO and +2.00 lenses binocnegative fusional vergence (NFV) group: BI and 2.00 lenses binocaccommodative (ACC) group: +2.00/2.00 monoc, acc ampsc.
Identify type of disorder based on near phoria or cover test.Classification of binocular disordersa.EXO at near:
receded near point of convergence, low BO,
fails + facilityconvergence insufficien Key test: NPC with penlight and red lensb.
ESO at near:
reduced BI at near, fails BI facilityconvergence excess fails 2.00 on binocular accom facilityKey Test: 2.00 flippers binoc.Classification of accommodative disordersaccommodative insufficiency low accommodative amplitude, can decrease with repeated testingNOT ENOUGHfails 2.00 monocular and binocularKey Test: +2.00/2.00 flippersaccommodative excess (spasm) variable visual acuity findings and refractionTOO MUCHfails +2.00 monocular and binocularKey Test: +2.00/2.00 flippersFourmost common diagnoses1.convergence insufficiency EXO2.convergence excess 3.accommodative insufficiency4.
4 4 .
Sequential Treatment Approach1.Optical correction of refractive errora.uncorrected refractive errors can:result in over or under accommodationresult in a high phoriaanisometropia can disrupt fusionreduce fusional ability due to retinal image blurcorrect significant refractive errors and retest accommodation and binocularity in 46 weeksmaximum plus for eso deviationsminimum plus for exo deviations2.
most effective for eso conditionsb.added plus lenses work well for:convergence excessaccommodative insufficiency3.
Prisma.helpful when vision therapy is not practical or effectiveb.most effective for divergence insufficiency and vertical deviationsc.
prescribe using fixation disparity(associated phoria)4.Vision therapy (orthoptics)a.has been shown to:increase accommodative amplitudes and facility, decrease latency of accommodative response, eliminate accommodative spasmincrease fusional vergence amplitudes and facilityeliminate suppression, improve stereopsisb.VT works very well with
convergence insufficiency and accommodative excess, where plus lenses dont work welldivergence is trainable convergence excess studyvery good prognosis for all accommodative and nonstrabismic horizontal deviations except divergence insufficiency e.
age, intelligence, and motivationlength oftherapy 24 monthsare important considerations.
VT TreatmentOptions1.Office based VT vs.home based VTHTS (Home Therapy Systems)Advantages: inexpensive, Windows/Mac compatible, easy to use, automatic and manual modes, internetmonitoring of compliance, excellent results with motivated patients, good tech supportvergence, vergence facility, accommodative facility, pursuits and saccadesDisadvantages: pursuits and saccades not very engaging, accommodativetherapy is biocularcan add binocular flippers, brock string, or pencil pushups if needed3.
over $30,000/yr (gross) .Case StudiesREFERENCES1.Scheiman and Wick, Clinical Management of Accommodative, Nonstrabismic Binocular Vision and Eye Movement Disorders.
(3rded)Lippincott Publishers, Philadelphia, PA, USA, 20082.Griffin and Grisham, Binocular Anomalies: Diagnosis and Vision Therapy Ed), ButterworthHeinemann Publishers, Boston, MA, USA, 2002.3.Richman and Cron, Bernell Guide to Vision Therapy, South Bend, IN, USA, 14.
Home Therapy System (HTS) , homevisiontherapy.comCITT Study Group, Randomized clinical trial of treatments for sy
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