Pharm chapter 20 exam 3 cholinergic drugs

What are cholinergic drugs?

 Drugs that stimulate the parasympathetic nervous system (PSNS)

What is the parasympathetic nervous system (PSNS)?

The opposing system to the sympathetic nervous system

Cholinergic drugs are also known as:

cholinergic agonist or parasympathomimetics

Cholinergic drugs mimic effects of the PSNS neurotransmitter:

acetylcholine (ACh)

Where are nicotinic receptors?

in ganglia of both PNS and SNS 

Where are muscarinic receptors?

in postsynaptic effector organs: smooth muscle, cardiac muscle and glands

Why are nicotinic receptors named nicotinic?

 because they can be stimulated by the alkaloid nicotine

Nicotinic receptors create what response?

Undesirable excitable response

Why are muscarinic receptors called muscarinic?

because they can be stimulated by the alkaloid muscarine as substance isolated from mushrooms

Muscarinic receptors create what response?

Desirable response

Direct acting cholinergic agonists mechanism of action

Bind to cholinergic receptors, activating them

Indirect acting cholinergic agonists mechanism of action

◦Also known as cholinesterase inhibitors

◦Inhibit the enzyme acetylcholinesterase, which breaks down ACh

◦Results in more ACh available at the receptors

Reversible indirect acting cholinesterase inhibitors:

Bind to cholinesterase for a short period of time

Irreversible indirect acting cholinesterase inhibitors

•Bind to cholinesterase for a long period of time

•Bind to cholinesterase and form a permanent covalent bond

•The body must make new cholinesterase to break these bonds.

The PNS is the

“rest and digest” system

The sympathetic nervous system is the

“fight or flight” system

Cholinergic drugs effects are seen when

PSNS is stimulated

Mechanism of action and effect of cholinergic drugs

 After binding, permeability of the cell changes allowing flow of calcium and sodium into the cells.

 Results in depolarization of cell membrane and stimulation of the effector organ

Mechanism of action of cholinergic drugs on GI system

◦Increased gastric secretions

◦Increased gastrointestinal motility

◦Increased urinary frequency

Mechanism of action of cholinergic drugs on eyes

 Stimulate pupils

◦Constriction (miosis)

◦Reduced intraocular pressure

Mechanism of action of cholinergic drugs SLUDGE

◦Salivation/sweating

◦Lacrimation (includes pupil constriction, reducing ocular pressure)

◦Urinary frequency

◦Diarrhea

◦Gastric motility- GI cramps, passage of gas

◦Emesis

Cholinergic drugs have some but very little effects of

 Cardiovascular effects

◦Decreased heart rate

◦Vasodilation

 Respiratory effects

◦Bronchial constriction, narrowed airways

Desirable and undesirable effects of cholinergics

 Desired effects are from muscarinic receptor stimulation.

Many undesirable effects are caused by stimulation of nicotinic receptors.

At recommended doses, cholinergics

primarily affect muscarinic receptors

At high doses, cholinergics

stimulate nicotinic receptors

Indirect acting cholinergic cause increase in…

◦ACh concentrations at the receptor sites, which leads to stimulation of the effector cells

◦ Cause skeletal muscle contractions

Contraindications for cholinergic drugs

Known drug allergy

GI or genitourinary (GU) tract obstruction

Adverse effects of cholinergics

GI effects, abdominal cramps, passage of gas/flatus increased secretions, nausea, vomiting, other such as lacrimation, sweating, salivation, miosis

Signs of cholinergic OD

 Circulatory collapse, hypotension, bloody diarrhea, shock, and cardiac arrest, early signs being SLUDGE, Abdominal cramps, salivation, flushing of the skin, nausea, and vomiting. Transient syncope, transient complete heart block, dyspnea, and orthostatic hypotension may also occur 

Treatment of a cholinergic OD

•Treatment in early phase: atropine, a cholinergic antagonist

•Treatment of severe cardiovascular reactions or bronchoconstriction: epinephrine, an adrenergic agonist

Interactions for anticholinergics, antihistamines, and sympathomimetics

Antagonize cholinergic drugs, resulting in decreased responses

Before giving cholinergic drugs the nurse should asses for

allergies, presence of GI or GU obstructions, asthma, peptic ulcer disease,
and coronary artery disease

Patients with myasthenia gravis should take cholenergics meds….

30 minutes before eating to help improve chewing and swallowing

When cholinergic drugs are prescribed for Alzheimer’s disease, be honest with caregivers and patients that the drugs are for

management of symptoms, not a cure

What is the antidote for cholinergics

Atropine

Atropine should be available where?

In the patients room for immediate use if needed

What is myasthenia gravis?

a chronic autoimmune neuromuscular disease characterized by fluctuating muscle weakness