Unit 8: Medications for the CNS

Dopamine Replacement Drugs

(Levodopa + Carbidopa)

Drugs that increase dopamine levels in the brain by converting levodopa into dopamine, helping improve movement symptoms like tremors and rigidity. Carbidopa prevents breakdown before reaching the brain. Side effects include dyskinesias and nausea, and long-term use can cause motor fluctuations

Non-dopamine dopamine receptor agents

Drugs that directly stimulate dopamine receptors in the brain without needing conversion. Used in early or advanced Parkinson’s. Can cause drowsiness, hallucinations, and impulse control issues like gambling or hypersexuality

MAO-B Inhibitors

Drugs that block the enzyme that breaks down dopamine in the brain, allowing more dopamine to stay active. Used for mild symptoms or with levodopa. Can cause insomnia and have interactions with antidepressants that may lead to serotonin syndrome

COMT Inhibitors

Drugs that prolong the effect of levodopa by preventing its breakdown in the body, increasing dopamine availability. Used only with levodopa. Side effects include diarrhea and worsening dyskinesias

Dopamine Modulators

Drugs that increase dopamine release and block its reuptake, helping improve symptoms like tremor and rigidity. Also used for dyskinesias. Can cause confusion, hallucinations, and livedo reticularis (skin mottling)

Anticholinergics

Drugs that reduce acetylcholine activity to restore balance with dopamine, mainly helping tremors. Not commonly used in older adults due to side effects like dry mouth, constipation, urinary retention, and confusion

Dyskinesia

Involuntary, uncontrolled movements often caused by long-term levodopa use

On-Off Phenomenon

Sudden changes between mobility and immobility in patients taking levodopa

Serotonin Syndrome

A potentially life-threatening condition caused by excess serotonin, especially when MAO-B inhibitors are combined with antidepressants

Impulse Control Disorders

Behaviors like gambling, shopping, or hypersexuality linked to dopamine agonists

Livedo Reticularis

A lace-like purplish discoloration of the skin associated with amantadine

Cholinesterase Inhibitors

(Donepezil, Rivastigmine, Galantamine)

Drugs that increase acetylcholine levels in the brain by preventing its breakdown, helping improve memory and cognition in mild to moderate Alzheimer’s. Common side effects include nausea, vomiting, diarrhea, and bradycardia due to increased cholinergic activit

NMDA Receptor Antagonists

(Memantine)

Drugs that regulate glutamate activity in the brain to prevent overstimulation and neuronal damage, used in moderate to severe Alzheimer’s. Helps with cognition and daily function. Side effects include dizziness, confusion, and headache

Acetylcholine

A neurotransmitter important for memory and learning that is decreased in Alzheimer’s disease

Glutamate

A neurotransmitter involved in learning and memory, but excess levels can cause brain cell damage in Alzheimer’s

Bradycardia

Slow heart rate that can occur with cholinesterase inhibitors

Neurodegeneration

Progressive loss of brain cells that leads to memory loss and cognitive decline

Benzothiazoles

(Riluzole)

Drugs that reduce glutamate activity in the brain, helping prevent excitotoxic damage to motor neurons and slowing disease progression. May extend survival. Side effects include liver toxicity and fatigue

Antioxidants

(Edaravone)

Drugs that reduce oxidative stress and free radical damage in neurons, helping slow functional decline in ALS. Side effects include headache, bruising, and gait disturbance

Antisense Oligonucleotides

(e.g. Tofersen)

Drugs that target and reduce production of abnormal proteins caused by genetic mutations (like SOD1), helping protect motor neurons. Used in specific genetic forms of ALS. Side effects may include headache and injection-related reactions

Histone Deacetylase Inhibitors

Drugs that modify gene expression to support neuron survival and reduce neurodegeneration. Still being studied but may help slow disease progression by protecting motor neurons

Glutamate Excitotoxicity

Excess glutamate causing overstimulation and damage to neurons, a key mechanism in ALS progression

Oxidative Stress

Cell damage caused by free radicals, contributing to neuron death in ALS

Motor Neurons

Nerve cells responsible for muscle movement that progressively degenerate in ALS

SOD1 Mutation

A genetic mutation linked to some forms of ALS that leads to toxic protein buildup

Barbiturates

(Phenobarbital)

Drugs that enhance GABA activity in the brain, causing CNS depression and stabilizing neuronal activity to prevent seizures. Used for generalized and focal seizures. Side effects include sedation, respiratory depression, and risk of dependence

GABA

The main inhibitory neurotransmitter in the brain that helps calm neuronal activity and prevent seizures

Sodium Channel Blockers

Mechanism where drugs prevent rapid firing of neurons by stabilizing sodium channels, reducing seizure activity

Teratogenic Effects

Risk of birth defects associated with some antiepileptic drugs, important in pregnancy considerations

First-Line Antiepileptic Drugs

Drugs used as the initial treatment for seizures because they are most effective and safest for a specific seizure type. Usually given alone (monotherapy) to minimize side effects

Adjunct (Add-On) Antiepileptic Drugs

Drugs added to first-line therapy when seizures are not well controlled. Used in combination therapy to improve seizure control but increase risk of side effects and interactions

Interferon Betas

Drugs that modulate the immune system by reducing inflammation and slowing damage to myelin, helping decrease relapse frequency in MS. Side effects include flu-like symptoms, injection site reactions, and possible liver dysfunction

Monoclonal Antibodies

(e.g. Natalizumab, Ocrelizumab)

Drugs that target specific immune cells and prevent them from attacking the nervous system, significantly reducing relapses and disease progression. Side effects include infusion reactions and increased risk of serious infections

S1PR ModulatorsS1PR Modulators

Drugs that trap lymphocytes in lymph nodes, preventing them from reaching the brain and spinal cord, thereby reducing immune attacks. Used to decrease relapse rates. Side effects include bradycardia (especially first dose), infection risk, and liver issues

SSRI

Drugs that increase serotonin levels by blocking its reuptake in the brain, making more serotonin available. First-line treatment for depression due to better safety profile. Side effects include nausea, insomnia, and sexual dysfunction. Can cause serotonin syndrome if combined with other serotonergic drugs

SNRI

Drugs that increase both serotonin and norepinephrine levels, helping improve mood and energy. Used when SSRIs are not effective. Side effects include increased blood pressure, insomnia, and similar effects to SSRIs

Tricyclic Antidepressants

Older drugs that increase serotonin and norepinephrine but also affect other receptors, leading to more side effects. Used when other treatments fail. Side effects include sedation, weight gain, anticholinergic effects (dry mouth, constipation), and risk of cardiac toxicity in overdose

MAOI

Drugs that block the enzyme that breaks down serotonin, norepinephrine, and dopamine, increasing their levels. Used for treatment-resistant depression. Require strict dietary restrictions to avoid hypertensive crisis. Side effects include dizziness and dangerous increases in blood pressure

Tyramine

A substance found in aged cheeses, cured meats, and fermented foods that can trigger hypertensive crisis with MAOIs

Benzodiazepines

(e.g. Lorazepam, Diazepam)

Drugs that enhance GABA activity in the brain, producing a rapid calming effect. Used for acute anxiety, panic attacks, and short-term management. Side effects include sedation, dizziness, respiratory depression, and high risk of dependence and withdrawal

Buspirone

A drug that affects serotonin receptors to reduce anxiety without causing sedation or dependence. Used for chronic anxiety, not effective for immediate relief. Side effects include dizziness, headache, and nausea

Mood Stabilizers

(e.g. Lithium)

Drugs used to control mania and stabilize mood in bipolar disorder by affecting neurotransmitter activity. Effective for preventing manic episodes. Side effects include tremor, weight gain, and toxicity risk. Requires regular blood monitoring due to narrow therapeutic range

1st Generation (Conventional) Antipsychotics

Drugs that strongly block dopamine receptors, reducing symptoms of psychosis such as hallucinations and delusions. Effective but associated with high risk of extrapyramidal side effects (EPS) like tremors, rigidity, and tardive dyskinesia

2nd Generation (Atypical) Antipsychotics

Drugs that block both dopamine and serotonin receptors, treating psychosis with lower risk of EPS compared to first-generation drugs. Also used for mood stabilization. Side effects include weight gain, diabetes risk, and metabolic syndrome

Extrapyramidal Symptoms

Movement disorders such as tremors, rigidity, and restlessness caused by dopamine blockade, common with first-generation antipsychotics

Tardive Dyskinesia

Late-onset, irreversible involuntary movements (like lip smacking) associated with long-term antipsychotic use

Neuroleptic Malignant Syndrome

A rare but life-threatening reaction to antipsychotics causing high fever, muscle rigidity, and altered mental status

Lithium Toxicity

A dangerous condition caused by high lithium levels, leading to confusion, tremors, and possible seizures

Metabolic Syndrome

A group of conditions including weight gain, high blood sugar, and increased cardiovascular risk, often seen with atypical antipsychotics

Amphetamines

(e.g. Adderall, Methylphenidate)

Stimulant drugs that increase dopamine and norepinephrine levels in the brain, improving attention and reducing hyperactivity. First-line treatment for ADHD. Side effects include insomnia, decreased appetite, weight loss, and increased heart rate and blood pressure. Risk of misuse and dependence

Non-Amphetamines

(e.g. Atomoxetine)

Non-stimulant drugs that increase norepinephrine levels to improve focus and attention. Used when stimulants are not tolerated or contraindicated. Side effects include fatigue, decreased appetite, and possible liver issues, but lower risk of misuse compared to stimulants

Miscellaneous Sedative-Hypnotics

(e.g. Z-drugs like Zolpidem)

Drugs that act on GABA receptors to promote sleep with less risk of dependence compared to benzodiazepines. Used for insomnia. Side effects include dizziness, drowsiness, and unusual behaviors like sleepwalking