Pharmacological Effects Of The Cholinergic Blockers

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The cholinergic blockers produce specific effects on certain organs in the body. These effects are:

a. Stomach/Intestines. The effect of the cholinergic blockers on the stomach and intestines is decreased activity.

b. Salivary Glands. The cholinergic blockers produce a drying effect.

c. Eye (Pupil). The cholinergic blockers produce dilation of the pupil (mydriasis).

d. Urinary Bladder. The cholinergic blockers produce urinary retention.

e. Heart. Increased heart rate is the effect produced on the heart by the cholinergic blockers.

f. Bronchi. The cholinergic blockers dilate the bronchi. 10-3. CLINICAL USES OF THE CHOLINERGIC BLOCKERS

The clinical uses of these drugs are based upon their normal pharmacological actions. Their most common clinical uses are listed below:

a. Antispasmodics. Antispasmodics are used to slow the motility of the gastrointestinal (GI) tract and reduce gastric secretions. Antispasmodics are commonly prescribed with other types of medications for patients who have ulcers or other GI disorders.

b. Mydriatics/Cycloplegics. These agents are used to produce pupil dilation (mydriasis) and to paralyze the muscles of accommodation (cycloplegia). In other words, these drugs prevent the eye from focusing. Medications used for these purposes are commonly used following ocular surgery and for certain types of eye examinations.

c. Antiparkinsonism Agents. These drugs are used to treat Parkinsonism, a condition characterized by excessive cholinergic activity in the brain. This condition results in an inability to perform fine motor movements.

d. Cold Preparations. Many over-the-counter and legend cold preparations contain cholinergic blocking agents. These cholinergic blockers help to dry secretions (that is, help to "dry" a runny nose).

e. Antidote for Nerve Gas Poisoning. Some cholinergic blocking drugs are used as antidotes for persons who have been poisoned by nerve gases (irreversible cholinesterase inhibitors). Certain cholinergic blocking agents are also used as antidotes for certain insecticides (irreversible cholinesterase inhibitors).

f. Treatment of Bradycardia (Slow Heart Rate). Atropine sulfate, a cholinergic blocker, is sometimes administered to a patient following cardiac arrest to increase the heart rate. By blocking cholinergic innervation to the heart, sympathetic nerves are allowed to override and increase the rate of the heart.

g. Preoperative Medication. Certain cholinergic blockers are administered to patients immediately before their undergoing a surgical procedure. In this case, the cholinergic blockers help to dry secretions in the mucous membranes.

a. Atropine. Atropine is a classic example of the cholinergic blockers. It is found alone and in combination with a wide-variety of other drugs. As an ophthalmic preparation (Isopto-Atropine®), it is used as a cycloplegic and as a mydriatic. Side effects associated with the use of atropine are unsteadiness, hallucinations, unusual dryness of mouth, and increased sensitivity of eyes to light. Patients who have glaucoma should use caution when using this preparation.

b. Scopolamine. Scopolamine is another classic example of the cholinergic blockers. Like atropine, scopolamine is found in a variety of medications. It is found in some over-the-counter cold medications. It is present in these products because of the drying effect it produces. In its ophthalmic form it is used as a mydriatic and as a cycloplegic. Side effects that can be caused by this drug include unsteadiness, fever, flushing, or redness of the face, hallucinations, and increased sensitivity of the eyes to light. Patients who have glaucoma should use this preparation with caution.

c. Homatropine Hydrobomide (Isopto-Homatropine®). This ophthalmic preparation is used as a mydriatic and as a cycloplegic. The side effects associated with this drug are the same as those associated with atropine and scopolamine (above). Patients who have glaucoma should use this preparation with caution.

d. Cyclopentolate (Cyclogyl®). This cholinergic blocker is used as a mydriatic and as a cycloplegic. Cyclopentolate can produce side effects such as unsteadiness, fever, redness of the face, hallucinations, or increased thirst. Patients who have glaucoma should use Cyclopentolate with caution.

e. Belladonna Alkaloids with Phenobarbital (Donnatal®). This preparation is used as an antispasmodic. Side effects associated with this agent are eye pain (from increased intraocular pressure), constipation, drowsiness, and dryness of the mouth. Patients taking this preparation should be informed of several things. Do not drink alcohol while taking Donnatal® (because of central nervous system depression). Never take this preparation within one hour of taking antacid (the effectiveness of the Donnatal® will be reduced). This drug may cause drowsiness in some patients; therefore, know how the drug will affect him before he drives or performs any job that requires alertness. Belladonna alkaloids sometimes make patients perspire less (this results in increased body temperature); therefore, do not become overheated because of excessive exercise or hot weather.

f. Propantheline Bromide (Pro-Banthine®). This agent is used in the treatment of peptic ulcers. Side effects associated with this drug include constipation, difficult urination (because of decreased muscle tone of the urinary bladder), eye pain (from increased intraocular pressure), and dizziness. Patients taking this medication should be informed of several things. Propantheline can produce drowsiness in some patients; therefore, they should ensure they know how the medicine will affect them before they drive or perform activities that require mental alertness. Sometimes patients taking this medication perspire less; therefore, they should ensure they do not become overheated because of excessive exercise or hot weather. Patients that have glaucoma or severe heart disease should use this drug with caution.

g. Belladonna Tincture. This preparation is used for its antispasmodic effect on the gastrointestinal tract (effect produced chiefly by its atropine content). Side effects associated with this agent include dryness of the mouth, dizziness, and constipation.

h. Dicyclomine (Bentyl®). This preparation is used to relieve smooth muscle spasm of the gastrointestinal tract. Side effects that can be caused by this drug include constipation (caused by decreased peristalsis), difficult urination, and dizziness. Persons taking this drug should be cautioned against taking alcohol or other central nervous system (CNS) depressants.

i. Trihexyphenidyl (Artane®). This drug is used in the treatment of parkinsonism. Side effects that can be caused by trihexyphenidyl include constipation, difficult urination, dizziness, dry mouth, and reduced perspiration. Patients taking this preparation should be told several things. Do not take with alcohol or other central nervous system depressants. Some patients perspire less; therefore do not become overheated because of exercise or hot weather.

j. Benztropine (Cogentin®). Benztropine is used in the treatment of parkinsonism. The side effects and patient instructions for trihexyphenidyl (Artane®), above, also apply to benztropine.

IMPORTANT NOTE: Sometimes trihexyphenidyl (Artane®) and benztropine

(Cogentin®) will be prescribed with certain phenothiazine tranquilizers to help reduce some of the centrally induced side effects produced by the tranquilizers.

NOTE: Drugs listed in k and l below are both antiparkinsonism drugs; however, they are NOT cholinergic blockers.

k. Levodopa (Larodopa®). This drug is used in the treatment of parkinsonism. Side effects associated with this agent include depression, difficult urination, unusual and uncontrolled movements of the body (that is, face, tongue, and arms), and mood changes. Patients taking this drug should be informed of several things. Take this medication with solid food to decrease the possibility of stomach upset. This drug may cause drowsiness in some patients; therefore, know how the drug will affect him before he drives or performs any job that requires alertness). This drug may cause dizziness or fainting in some patients; therefore, persons taking the drug should get up slowly from a lying or sitting position.

l. Carbidopa and Levodopa (Sinemet®). This preparation is used in the treatment of parkinsonism. Side effects that can be caused by this medication include mental depression) mood changes, unusual and uncontrolled movements of the body (that is, face, tongue, arms), and difficult urination. Patients taking this product should be informed of several things. Patients need to take this medication with solid food to decrease the possibility of stomach upset. This drug may cause drowsiness in some patients; therefore, know how the drug will affect him before he drives or performs any job that requires alertness. This drug may cause dizziness or fainting, persons taking the drug should get up slowly from a lying or sitting position.

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  • ruari burns
    What effect is produced with cholinergic blockers?
    6 months ago

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