9.4 Nervous System Medications

Susanne Erickson; Lisa Sturdy

9.4 Nervous System Medications

The most common medications and medication categories for conditions of the nervous system are discussed below. Some conditions, such as multiple sclerosis, are very complex to treat and involve many medications, and as such, those pathologies and the medications used to treat them are not included below.

Anticonvulsants

Medications used for seizures are called anticonvulsants. Anticonvulsant medications stabilize cell membranes and suppress the abnormal electric impulses in the cerebral cortex. These medications prevent seizures but do not provide a cure. Anticonvulsants are classified as central nervous system depressants. There are many types of medications used to treat seizures, including phenytoin (Dilantin), phenobarbital (Luminal), benzodiazepines, carbamazepine (Tegretol), valproate (valproic acid), and levetiracetam (Keppra).

There are three main pharmacological effects of anticonvulsant medications. First, they increase the threshold of activity in the motor cortex, making it more difficult for nerves to become excited. Second, they limit the spread of a seizure discharge from its origin by suppressing the transmission of impulses from one neuron to the next. Third, they decrease the speed of nerve impulse conduction within a given neuron.

Hydantoin Medications

Phenytoin (Dilantin), which was discovered in 1938, is categorized as a hydantoin medication. It was the first anti-seizure medication and is still being used to control seizures. Phenytoin lessens the incidence of seizures by interfering with sodium channels in the brain, resulting in a reduction of sustained high-frequency neuronal discharges.

Phenytoin has a narrow therapeutic drug level, usually 10–20 mcg/mL, so serum drug monitoring is required. Serum levels of phenytoin sustained above the therapeutic range may produce delirium, psychosis, and encephalopathy, which means it is important, at the first sign of acute toxicity, for serum levels to be immediately checked.

Key Concept

A common suffix for hydantoin medications for epilepsy is -toin.

Examples: ethotoin (Peganone), fosphenytoin (Cerebyx), phenytoin (Dilantin)

Benzodiazepine Medications

Benzodiazepine medications exert an anticonvulsant effect on receptors in the brain stem. These medications can also be administered for other therapeutic reasons and for many other pathologies that have been, or will be covered, in this book. Lorazepam, a benzodiazepine with anti-anxiety, sedative, and anticonvulsant effects, is available for oral, intramuscular, or intravenous routes of administration. Some of the various medication forms that lorazepam is offered in are shown in Figs. 9.10 and 9.11. Benzodiazepines are a controlled Schedule IV substance because they have the potential for abuse and may lead to dependence.

Key Concept

A common suffix for benzodiazepines is -azepam.

Examples: clonazepam (Klonopin), diazepam (Valium), lorazepam (Ativan)

Barbiturate Medications

The therapeutic actions of barbiturate medications include long-acting sedative and anticonvulsant effects. Phenobarbital is an example of a barbiturate primarily used as a sedative and to treat seizure disorders. In high doses, it can be used to induce anesthesia, and overdose can cause death. In the 1960s and 1970s, barbiturates were used to treat anxiety and insomnia but are no longer used for these purposes because of the serious adverse effects of these drugs.

Key Concept

A common suffix for barbiturate medications is -barbital.

Examples: mephobarbital (Mebaral), phenobarbital (Luminal)

Levetiracetam

Levetiracetam is indicated as adjunctive therapy in the treatment of partial onset seizures in patients with epilepsy and is generally well tolerated. The exact mechanism of action is unknown, but this medication may interfere with sodium, calcium, potassium, or GABA transmission. Withdrawal seizures may occur if levetiracetam is stopped abruptly.

Gabapentin

Gabapentin is indicated as an adjunctive treatment for partial seizures, but it is most commonly used to treat neuropathic pain. An example of neuropathic pain is tingling or burning in the lower extremities that often occurs in patients with diabetes. The exact mechanism of action is unknown.

Antiparkinson Medications

Parkinson’s disease is believed to be related to an imbalance of dopamine and acetylcholine and a deficiency of dopamine in certain areas of the brain, so drug therapies are aimed at increasing levels of dopamine and/or antagonizing the effects of acetylcholine. Drug therapy does not cure the disease but is used to slow the progression of symptoms. Common medications used to treat Parkinson’s disease are carbidopa/levodopa, selegiline, and amantadine.

Carbidopa/Levodopa

Carbidopa/levodopa, shown in Fig. 9.12, is the most common drug used to treat Parkinson’s disease and is usually started as soon as the patient becomes functionally impaired. The administration of dopamine is ineffective in the treatment of Parkinson’s disease because it does not cross the blood-brain barrier, but levodopa, the metabolic precursor of dopamine, does cross the blood-brain barrier and presumably is converted to dopamine in the brain. Carbidopa is combined with levodopa to help stop the breakdown of levodopa. Additionally, the incidence of levodopa-induced nausea and vomiting is less when levadopa is combined with carbidopa.

Selegiline

Selegiline is often used in conjunction with carbidopa/levodopa when patients demonstrate a deteriorating response to that treatment; it is helpful for controlling symptom fluctuations. Selegiline inhibits MAO-B, blocking the breakdown of dopamine. There is no evidence from controlled studies that selegiline has any beneficial effect in the absence of concurrent levodopa therapy.

Amantadine

Amantadine is used in the early stages of Parkinson’s disease, but it can be effective in moderate or advanced stages in reducing tremors and muscle rigidity. The exact mechanism of action is unknown, but it is an antiviral drug that acts on dopamine receptors.

None of these medications can cure Parkinson’s, and over time, it is not uncommon for tolerance to these medications to increase, so the dose often needs to be increased to maintain the same therapeutic effect. Eventually, the side effects also become worse, so at a certain point, the physician may place the patient on a “drug holiday.” This means the patient stops taking medications for a few days, then restarts at a lower dose.

Alzheimer’s Medications

The most common medication given for Alzheimer’s disease is donepezil (Aricept) (WebMD, 2022). Although this medication, and all others, will not prevent the progression of this disease, they will often slow the development and enable patients to have better standard of living. Other common medications are galantamine (Razadyne) and tacrine (Cognex) (WebMD, 2022). Rivastigmine (Exelon) is another option and can be given via a transdermal patch that only needs to be changed once a day (WebMD, 2022). This is ideal when Alzheimer’s, or other types of dementia, become advanced, and patients are uncooperative when taking oral medications.

Insomnia Medications

Many patients with neurological disorders also have insomnia. Although anyone can experience insomnia, those with any of the nervous system pathologies discussed in this chapter are more susceptible (Betts et al., 2013). Insomnia is generally characterized by difficulty falling asleep, difficulty staying asleep, or difficulty getting back to sleep. There are many factors that can make insomnia worse, including stress, anxiety, and pain (Betts et al., 2013). Typically, medications used to treat insomnia are classified as hypnotics or sedatives.

Nonbarbiturate Hypnotic or Sedative Medications

Nonbarbiturate hypnotic or sedative medications work by depressing the central nervous system in order to produce sedation and sleep. They are regulated because they have the potential for addiction. Some examples of these types of medications include the following:

Chloral hydrate (Somnote)
Zopiclone (Imovane)
Zolpidem (Ambien, Intermezzo, Zopimist)

Anti-Anxiety (Benzodiazepines) and Antidepressant Medications

Certain medications, which can also be prescribed for anxiety or depression, may also be given for insomnia. Some of them are listed below:

Anti-anxiety medications:
- Flurazepam (Dalmane)
- Temazepam (Restoril)
- Triazolam (Halcion)

Antidepressant drugs for insomnia:
- Doxepin (Silenor)
- Trazodone (Oleptra)

Melatonin

The hormone melatonin is secreted by the pineal gland and regulates the 24-hour wake-sleep cycle (Betts et al., 2013). Melatonin, shown in Fig. 9.13, can be purchased over the counter (OTC) and used to stimulate the melatonin receptors, resulting in an increased desire to sleep. It is one of the few non-prescription sleep aids available (Betts et al., 2013).

Table 9.1. Common Nervous System Medications

Generic	Trade	Reason For Administering
carbamazepine	Tegretol	seizure disorders
valproate	Valproic acid	seizure disorders
ethotoin	Peganone	seizure disorders
fosphenytoin	Cerebyx	seizure disorders
gabapentin	Neurontin	seizure disorders
levetiracetam	Keppra	seizure disorders
mephobarbital	Mebaral	seizure disorders
phenobarbital	Luminal	seizure disorders
phenytoin	Dilantin	seizure disorders
amantadine	Gocovri	Parkinson’s disease
carbidopa/levodopa	Sinemet	Parkinson’s disease
selegiline	Eldepryl, Emsam	Parkinson’s disease
donepezil	Aricept	Alzheimer’s disease/dementia
razadyne	Galantamine	Alzheimer’s disease/dementia
rivastigmine	Exelon	Alzheimer’s disease/dementia
tacrine	Cognex	Alzheimer’s disease/dementia
chloral hydrate	Somnote	Insomnia
zopiclone	Imovane	Insomnia
zolpidem	Ambien, Intermezzo, Zopimist	Insomnia
flurazepam	Dalmane	Insomnia/anxiety
temazepam	Restoril	Insomnia/anxiety
triazolam	Halcion	Insomnia/anxiety
doxepin	Silenor	Insomnia/depression
trazodone	Oleptra	Insomnia/depression

(WebMD, 2022)

Attribution

Unless otherwise indicated, material on this page has been adapted from the following resource:

Ernstmeyer, K., & Christman, E. (Eds.). (2020). Nursing pharmacology. Chippewa Valley Technical College. https://wtcs.pressbooks.pub/pharmacology/ licensed under CC BY 4.0

References

Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., Kruse, D. H., Korol, O., Johnson, J. E., Womble, M., & DeSaix, P. (2013). Anatomy and physiology. OpenStax. https://openstax.org/details/books/anatomy-and-physiology licensed under CC BY 4.0

WebMD. (2022). Drugs & medications A–Z. https://www.webmd.com/drugs/2/index

Image Credits (images are listed in order of appearance)

Loratsepaamiin_perustuvia_lääkkeitä by Melissan, Public domain

Lorazepam2mgmLvial by Stickpen, Public domain

Medicationlevodopa by Revion101, CC BY-SA 4.0

Melatonin_prescription by Murrur, CC BY-SA 3.0