Central Nervous System Functions

Central Nervous System Functions

• The CNS consists of the brain and spinal cord; spinal cord nerves are part of the PNS controlled by the brain.
• PNS nerves relay signals between the brain and body, connecting the CNS to organs, limbs, muscles, blood vessels, and glands.
• The CNS has many critical structures and actions that work together to ensure normal body functioning.
• Photoreceptor cells (rods and cones) in the retina detect and convert light into signals sent to the brain, which translates them into what we perceive.
• Problems inside or outside the CNS can affect brain function.
• Drug therapy addresses CNS problems affecting physical function, including Parkinson's, Alzheimer's, epilepsy, and multiple sclerosis.
• Movement is an essential motor function involving the brain, spinal cord, nerves, muscles, and bones.
• A neurotransmitter is a chemical released from a nerve ending, crossing the synaptic cleft and binding to receptors on the next nerve.
• Neurotransmitters can be either excitatory or inhibitory.
• Excitatory neurotransmitters include acetylcholine (ACh), epinephrine, and norepinephrine.
• Inhibitory neurotransmitters include dopamine, some types of serotonin, and gamma-aminobutyric acid (GABA).
• Smooth movement results from excitatory (ACh) and inhibitory (dopamine) neurotransmitter input.
• CNS problems like Parkinson's disease result from an imbalance of excitatory and inhibitory neurotransmitters.
• Epilepsy is caused by brain conditions causing unnecessary neuron excitation.
• Alzheimer's and multiple sclerosis result from degenerative changes in nerves or brain support cells.

Drugs for Parkinson's Disease (PD)

• PD is the second most common neurodegenerative disease after Alzheimer's, caused by a combination of genetic, protective, and environmental factors.
• PD incidence increases with age, but it can occur before age 50, affecting more men than women.
• PD diagnosis takes time due to the absence of a specific test, requiring the ruling out of other neurological diseases, and manifests as movement disorders associated with Lewy bodies in the brain.
• PD is a CNS disorder with insufficient dopamine available to modify excitatory signals to skeletal muscles.
• Dopamine, an inhibitory neurotransmitter, is mainly produced in the substantia nigra in the midbrain, part of the basal ganglia.
• Complications of PD include depression, hallucinations, anxiety, and delusions.
• Hallucinations and delusions result from PD changes or adverse effects of PD drugs.
• PD drugs elevate dopamine to improve motor symptoms, which can also cause hallucinations and delusions.
• PD worsens over time, eventually requiring total care; drug therapy can delay symptom progression and allow patients to remain independent longer.
• Drug therapy includes dopamine, dopamine agonists, COMT inhibitors, and MAO-B inhibitors.
• Anticholinergic drugs were previously a major therapy by balancing decreased dopamine by reducing ACh levels, but they did not address the main problem of lack of dopamine and these are no longer commonly used.

Dopamine Agonists: Action and Uses

• A dopamine agonist mimics natural dopamine, which balances acetylcholine and dopamine levels in the brain.
• The therapeutic effect reduces muscle tremors and rigidity that improves mobility, muscular coordination, and performance.
• Eventually, all patients require levodopa because dopamine becomes deficient.
• Levodopa is synthesized in the brain and converted to dopamine, making it a key drug for managing PD symptoms.
• Wearing off happens when a drug loses effectiveness after levodopa has been used for several years.
• Effectiveness of Levodopa usually peaks about 1 hour after administration, and wears off after 4 to 5 hours.

Dopamine Agonists: Side Effects, Adverse Reactions, and Interactions

• Side effects of carbidopa/levodopa and dopamine agonists include postural hypotension, headache, GI disturbances, insomnia, dream abnormalities, decreased impulse control, and confusion.
• Dyskinesia, resulting in involuntary uncoordinated-like dance movements, is a common adverse reaction, especially after more than 3 years on carbidopa/levodopa.
• Pramipexole, ropinirole, rotigotine, and other dopamine agonists can minimize dyskinesia.
• Dopamine agonists can cause delirium, psychosis, and hallucinations with the healthcare provider determining if symptoms relate to disease progression, depression, or the PD drug.
• Carbidopa/levodopa dosages may be decreased when COMT and MAO-B inhibitors are added, precipitating neuroleptic malignant syndrome (agitation, coma, muscle rigidity, tremors, high fever, unstable blood pressure).
• Risperidone combats psychosis associated with PD.
• Ropinirole treats PD symptoms such as stiffness, tremors, muscle spasms, and poor muscle control.
• Using antihypertensive agents with dopamine agonists can cause severe hypotension.
• Older, nonselective MAO inhibitors e.g. phenelzine (Nardil) with dopamine agonists can precipitate a hypertensive crisis.
• Phenytoin (Dilantin) reduces effectiveness of dopamine agonists.
• Multivitamins containing iron also decrease the effects of carbidopa/levodopa.
• Vitamin B6 increases levodopa metabolism without carbidopa.
• Metoclopramide (Reglan) reduces dopamine agonist effectiveness by preventing dopamine from combining with receptors.
• Combining dopamine agonists with sedatives worsens drowsiness and increases confusion, hallucinations, and delusions, especially in individuals already prone to mental illness.

Dopamine Agonists: Nursing Implications and Teaching

• Dopamine agonists cause postural hypotension; blood pressure readings should include orthostatic measurements (supine, sitting, and standing).
• Assess motor skills and functional ability for walking and eating to ensure safety from falls and aspiration.
• Review history for melanoma or closed-angle glaucoma, and these conditions contraindicate agonists.
• Closely monitor blood glucose due to levodopa causing sympathetic effects.
• Observe for hypoglycemia symptoms like headache, anxiety, shakiness, weakness, and irritability.
• Check BUN and creatinine before pramipexole because up to 90% is excreted by the kidneys.
• Monitor liver enzymes before and at intervals during treatment.
• Give dopamine agonists 30 to 60 minutes before meals for better absorption, so that patients have less difficulty chewing and swallowing.
• Extended-release tablets should never be crushed.
• Apply rotigotine transdermal patches at the same time every day and rotate application sites, and do not apply to the same site more than once every 14 days for skin reaction.
• Dopamine agonists should be withdrawn slowly due to long half-life.
• When changing preparations, start the new drug at a small dose, and withdraw the old drug dose gradually, with the dose increasing until the maximum therapeutic effect has been reached
• Dopamine agonists are available in patches, tablets, sustained-release capsules, syrups, and elixirs.
• They are well absorbed from the GI tract.
• Carbidopa/levodopa blood levels peak in 1-6 hours, depending on administration route.
• Plasma levels for Sustained-release capsules peak in 8-12 hours.
• Sustained-release capsules lack dosage regulation flexibility and are not recommended for initial therapy.
• Long-term use can lead to akinesia and dystonia.
• Doses should be reduced to the minimum effective level to reverse these effects, with very slow changes to avoid overmedication.
• Monitor all changes closely for behavior changes, such as worsening depression and psychosis.
• Report abnormal involuntary movements, such as chewing, tongue protrusion, or jerky movements because these can indicate dystonia related to disease progression or drug wearing off.

Patient and Family Teaching for PD

• Clinical improvements are cumulative (get better over time) and may take up to 3 weeks to have full effect; even if no changes appear to have taken effect, continue taking the drug
• If possible, take the drug on in empty stomach 30 to 60 minutes before meals so the drug can be absorbed better
• If nausea become a side effect, take the drug with some type of carbohydrate such as crackers, but avoid foods containing protein because it can counteract the effects of the drug
• Levodopa cannot be taken with vitamin B6 because it can speed up inactivation of the drug. This only applies when Levadopa is taken alone without Carbidopa
• Contact the healthcare provide immediately if there are intermittent winking/muscle twitching, or abdominal pain, incontinence, or anything else abnormal
• Along with the PD medication, use caution with any pain, sleep, muscle relaxing, or bladder control medications
• Move positions from lying down to standing up slowly due to low blood pressure
• Contact the healthcare provider if the patient develops hallucinations or delusions

Catechol-O-Methyltransferase Inhibitors: Action and Uses

• Catechol-O-methyltransferase (COMT) breaks down catecholamine-based neurotransmitters, including dopamine, and dopamine agonist drugs.
• The most common expected effects are GI upset and discoloration of the urine (brownish-orange color).
• Tolcapone is metabolized by the liver and leads to a higher risk of severe liver failure and is NOT to be used unless other measures have failed
• Monitoring the liver function for any signs of hepatic disease is required, it must be closely monitored every 6 months if tolcapone is used
• Neither entacapone, or tolcapone, should be taken with the MAO inhibitors because they can reduce catecholamine metabolism and cause severe cardiovascular problems
• Taking certain catecholamine drugs with entacapone-tolcapone can increase the heart rate, and lead to increased blood pressure
• The MAO-B inhibitors are considered to be safer with combo drugs due to being selective with blocking the breakdown of dopamine

COMT inhibitors: Nursing Implications and Teaching

• The patient can develop orthostatic hypertension, they should be reminded to stand up slowly to avoid imbalance
• Dyskinesia, and hyperkinesia should be monitored
• Entacapone is to be given with every single dose of carbidopa/levodopa, however tolcapone is with the first dose, and doses given 6 to 12 hours later
• Tolcapone requires monitoring for the patient to ensure there is no liver failure
• The patients should be evaluated for Dystonia, akinesia, and tardive dyskinesia due to these drugs being administered with levodopa
• Changes in behavior should be closely monitored due to an increased response to dopamine agonists

Catechol-O-Methyltransferase Inhibitors: Family Teaching

• Entacapone has to be administered each time levodopa/carbidopa is taken
• The first dose of tolcapone is to be administered with levodopa/carbidopa
• Any abdominal pain, swelling, and jaundice should be reported immediately due to the signs pointing to liver failure
• Any mental, delirium, or hallucination changes should be reported as well
• If the patient has these symptoms, do not stop the drugs abruptly, but start a tapering routine
• The urine turning a brownish orange color is normal and is not dangerous
• To prevent imbalance and dizziness, moving from a sitting position should be done slowly

MOA-B Inhibitors: Action and Uses

• MOA is formulated to be in the mitochondrial membranes
• The breakdown/metabolism of multiple substances is done by the enzymes
• MOA-B inhibitors can treat depression, but the breakdown of substances is reduced
• Has fewer side effects

MOA-B Inhibitors: Combinations, Results, and Side Effects

• Safinamide, selegiline, and rasagiline, (three MOA-B inhibitor drugs) are used in combination with carbidopa and levodopa
• Constipation, nausea, drowsiness, and dry mouth are effects that can occur, especially for older individuals
• Severe hypertension is an adverse effect that can occur with higher doses, but does not typically have the same lower doses
• Foods rich in tyramine should be avoided at all costs
• Photosensitivity also can increase, increasing the risk of sunburns, making the patient drowsy

MOA-B Inhibitors: Implications, Teaching, and Drug Interactions

• Opiate medicines such as tramadol, methadone, and meperidine should not be taken due to the risk of hypertensive crisis
• Tricyclic and MAO inhibitors can cause hyperthermia
• Ginseng and St. John's wort should be avoided

MOA-B Inhibitors: Nursing Implications and Teachings

• An assessment of the patient's vitals should be taken upon every dose increase, looking for any changes in behavior or pulse
• The patient should be educated that these drugs do take several weeks to begin working
• The prescribed dose is not to be exceeded, due to high blood pressure levels
• Any irregular heartbeats, nausea, heart pulse, or vomiting is to be reported to the healthcare provider
• Drowsiness is a common side effect
• The patients are also at higher risk for sunburn so caution must be taken

Drugs for Alzheimer's Disease

• AD is a common type of dementia, which causes impaired brain loss
• The symptoms of early AD include memory issues, the symptoms grow and increasingly worsen
• Drug therapy does not have a cure
• Drugs, for AD, only improve symptoms

Cholinesterase Inhibitors: Action and Uses

• Cholinesterase attempts to increase ACh levels
• Acetylcholinesterase, an enzyme, is known for specifically breaking down ACh
• Examples of Cholinesterase Inhibitors are Razadyne, Exelon, and Aricept

Cholinesterase Inhibitors: Actions and Side effects

• Treatment is to be done in AD, by using three AChE inhibitor drugs
• Common side effects that include Gl discomfort, headaches, loss of joint pain, appetite, and muscle cramping can occur
• Some adverse effects that include infection, bleeding, incontinence, and dysrythmias can occur
• Adverse cholinergic effects on the patients are known to happen to body systems, as they all undergo parasympathetic overstimulation

Implications and family/patient eduation of Cholinesterase Inhibitors:

• The cholinesterase inhibitor drugs should not be taken when the medication can cause a cardiac disorder, known as torsade de pointes
• A baseline should be assessed for every patient
• The patient needs to have weekly weight assessments
• If any Gl Bleeds occur, report the blood test levels
• The Alzheimer's Disease assessment scale should be used before starting therapy
• Asthma patients should be evaluated for any signs of worsening
• To lessen Gl upset, have a meal after taking, or snack after taking it
• Donepezil has to be taken at bedtime
• Galantamine/Rivastigmine is to be taken twice a day, with food
• Risk for falls increase due to possible weakness/dizziness symptoms
• Every checkup is crucial

N-Methyl-D-Aspartate Blockers: Action and Uses

• There are types of NMDA receptors in the brain; an activation of the brain creates more calcium, creating enhanced memory
• With too much overstimulation, neurons may be damaged
• N-methyl-D-aspartate is a calcium influx preventer
• Mematine (Namenda) is used with galantine to increase its effectiveness

N-Methyl-D-Aspartate Blockers: Adverse Reactions

• Memantine carries numerous expected side effects
• Hypertension in some individuals may be shown
• A large number of drug iterations, such as quinidine are expected

###N-Methyl-D-Aspartate Blockers: Nursing Implications and Patient Teaching

• Renal and Kidney disease should be approached with caution
• Levels of creatine should be obtained
• If there are any UTI symptoms found, report them and get a urinalysis
• Every dose should be given/taken at the same time
• If swallowing is a problem, sprinkle capsules onto the applesauce
• The patient should be advised on to never give these drugs with different mixes, due to the potential side effects and confusion can be shown
• If having, the extended release capsule may be sprinkled onto applesauce or another edible
• Confusion, dizzy spells, loss of breath, or rash should be reported immediately
• The patient is also expected to avoid hazardous activities

Drugs for Epilepsy and ALS

• Epilepsy is a disorder of the brain
• Convulsion = an uncontrolled response
• Seizures go to every part of the brain
• Every seizure side effect includes nausea, incontinence, drooling
• Seizures are classified as generalized and partial
• Head Trauma or other symptoms can cause seizures
• An AED is a drug used and it reduces seizures
• Newer and traditional categories are what AED drugs are divided into

Traditional AEDs

• This group involves many well-known and prescribed medications
• Most of the family/patient teaching is the same

Anti-Epilepsy drugs: Considerations

• Every drug that a patient is on must be known
• Levels of awareness, vitals, and gait are all important
• For the risk of defects, always find out if your patients are with child
• Always record the aura and sensation of each patient
• The call light is important

###Planning of Anti-Epilepsy Drugs

• The bed has to be always lowered for precautions
• Oxygen and equipment should be available in case something bad happens
• Monitor for the seizure
• Mental health must continuously be taken into account
• AEDs should never be mixed with depressants or alcohol
• To avoid further things happening, a AED drug should not be ceased suddenly