Pharmacological therapy - Neurological system Flashcards
Adrenergics
- drugs in this class include naturally occuring substances such as norepinephrine, epinephrine, and dopamine
- norepinephrine (NE) is the major neurotransmitter
- Dopamine is a key neurotransmitter in the CNS
Predominant Adrenergic Agonist Responses
- vasoconstriction
- CNS and ANS stimulation
- think fight or flight response: increase in BP, increase in responsivity of CNS
Receptors in the Sympathetic System
- adrenergic receptors with two subtypes Beta and Alpha
- Alpha 1 and Alpha 2
- Beta 1 and Beta 2
Beta-Adrenergic Receptors
- all are located on post-synaptic effector cells
- beta1-adrenergic receptors - located primarily in the heart
- beta2- adrenergic receptors - located in smooth muscle of the bronchioles, arterioles, and visceral organs
Treatment with receptor agonists:
alpha 1 - nasal congestion, hypotension, and mydriasis
alpha 2 - hypertension
beta 1 - cardiac arrest, heart failure, and shock. sometimes called cardiotonic or inotropic because they increase the force of contraction of the heart
- beta2 - asthma - relaxation of bronchial smooth muscle and premature labour contractions
Phenylephrine
- affects the alpha 1 receptors
- used during hypotension or for nasal congestion
- has few cardiac side effects
Adrenergic Antagonists ( Blockers)
- medications in this calls have great therapeutic application and are the most widely prescribed autonomic drugs. Mainly used for hypertension
- Bind to adrenergic receptors, but inhibit or block stimulation of the sympathetic nervous system
- alpha blockers and beta-blockers
- have the opposite effect o adrenergic agents
- also known as
Adrenergic antagonists
sympatholytics
sympatholytics inhibit - or lyse - sympathetic neurotransmitters, such as norepinephrine and epinephrine
Alpha-blockers
- cause both arterial and venous dilation, reducing peripheral vascular resistance and BP
- used to treat hypertension
- effect on receptors on prostate gland and bladder decreases resistance to urinary outflow, thus reducing urinary obstruction and relieving effects of BPH
- used to control and prevent hypertension in patient with phenochromacytoma
Alpha blockers: side effects
palpitations, orthostatic hypotension, tachycardia, edema, dysrhythmias, chest pain. Dizziness, headache, drowsiness. anxiety, depression, vertigo, weakness, numbness, fatigue, nausea, vomiting, diarrhea. constipation, abdominal pain, incontinence, nosebleed, tinnitus, dry mouth, pharyngitis, rhinitis
Beta-Blockers
- block stimulation of beta-receptors in the SNS
- compete with norepinephrine and epinephrine
- most common blood pressure medications
Beta 1 and 2 receptors
- located primarily on the heart
- beta-blockers selective for these receptors are called cardioselective beta-blockers
- beta 2 receptors located primarily on smooth muscles of bronchiles and blood vessels
- nonspecific beta-blockers block both beta1 and beta2 receptors
Beta-blocker examples
Acebutolol Carvedilol Labetalol Metoprolol Notice the OLOL!
Beta-Blockers may cause
- diarrhea
- stomach cramps
- nausea
- vomiting
Beta-Blocking Agents: Patient Teaching
- rebound hypertension or chest pain may occur if this medication is discontinued abruptly - dont do it
- patients should notify their physician if they become ill and unable to take medication
- ## Inform patients that they may notice a decrease in their tolerance for exercise, dizziness and fainting may occur with increased activity
Beta-Blocking Agents - Nursing Implications
patients should report the following to their physician
- weight gain of more than 2 pounds within a week
- edema of the feet or ankles
- shortness of breath
- excessive fatigue or weakness
- syncope or dizziness
Cholinergic Agonists and Antagonists
- drugs that stimulate the parasympathetic nervous system (PSNS) are cholinergic agonists
- the PSNS is the opposing system to the SNS
- Also known as parasympathomimetics
- mimic the effects of the PSNS neurotransmitter: acetylcholine (Ach)
- think rest and digest
Acetylcholine main neurotransmitter of the PSNS
- its all in the name
- Acetylcholine (neurotransmitter)
- stimulates or activates the next nerve cell as impulses move along a nerve from neuron to neuron or at the neural muscular junction simulating muscle stimulation
Cholinergics- Indications and Uses
- Direct-acting agents
reduce intraocular pressure
useful for glaucoma and intraocular surgery (acetylcholine, carbachol, pilocarpine)
topical application due to poor absorption
Cholinergics- Indications and Uses
- Direct-acting agents
reduce intraocular pressure
useful for glaucoma and intraocular surgery (acetylcholine, carbachol, pilocarpine)
topical application due to poor absorption
example of direct-acting cholinergic: Bethanechol
- increases tone and motility of bladder and GI trace
- relaxes sphincters in bladder and GI tract, allowing them to empty or drain. Remember cholinergic effect.
- helpful for post-surgical atony of the bladder and GI tract.
- oral dose or SC injection
Indirect Acting Agents - cholinergics
nonselective and allow the neurotransmitter to remain on cholinergic receptors for a long period of time
toxic side effects typical cholinergic poising presentation (SLUDGE)
Salivation Lacrimation Urinary incontinence Diarrhea GI cramps Emesis (too much of a good thing)
Cholinergic Blocking Agents: Anticholinergics
drugs that inhibit or block the actions of acetylcholine in the parasympathetic nervous system
- decreased parasympathetic = increased sympathetic
Mechanism of Action Anticholinergic
- competitive agonist
- compete with acetylcholine
- block ACh at the muscarinic receptors in the PSNS
- as a result, ACh is unable to bind to the receptor sites and cause a cholinergic effects
- Once these drugs bind to receptors, they inhibit nerve transmission at these receptors
