Unit 4 - Drug List

Pharmacology; Exam 4; Unit 4

Phenytoin (Dilantin, a Hydantoin)

Stabilizes neuronal membranes and prevents hyperexcitability caused by excessive stimulation; limits the spread of seizure activity from an active focus; has cardiac antiarrhythmic effects similar to those of lidocaine.

Indications for Phenytoin

Control of tonic-clonic and psychomotor seizures, prevention of seizures during neurosurgery, control of status epilepticus.

Pharmacokinetics of Phenytoin

Is well absorbed from the gastrointestinal (GI) tract, metabolized in the liver, and excreted in the urine.

Phenytoin Route #1

Route (Oral), Onset (Slow), Peak (2 to 12 hours), Duration (6 to 12 hours)

Phenytoin Route #2

Route (IV [Intravenous]), Onset (1 to 2 hours), Peak (Rapid), Duration (12 to 24 hours)

Contraindications for Phenytoin

Hypersensitivity, congenital anomalies (pregnancy), coma, depression, psychoses.

Cautions for Phenytoin

Impaired renal or liver function; Hepatic impairment.

Adverse Effects of Phenytoin

Ataxia, dysarthria, slurred speech, mental confusion, dizziness, fatigue, tremor, headache, dermatitis, Stevens-Johnson syndrome, nausea, gingival hyperplasia, liver damage, hematopoietic complications, sometimes fatal.

Clinically Important Drug-Drug Interaction for Phenytoin

Limit alcohol and other CNS depressants.

Phenobarbital (Solfoton, Luminal), a Barbiturate/Barbituratelike drug)

Long-term treatment of generalized tonic-clonic and cortical focal seizures, emergency control of certain acute convulsive episodes (status epilepticus, tetanus, eclampsia, meningitis), and anticonvulsant treatment of generalized tonic-clonic seizures and focal seizures (parenteral).

Indications for Phenobarbital

General CNS depressant; inhibits impulse conduction in the ascending RAS; depresses the cerebral cortex; alters cerebellar function; depresses motor output; and can produce excitation, sedation, hypnosis, anesthesia, and deep coma.

Pharmacokinetics of Phenobarbital

Available in oral and parenteral forms, is well absorbed from the GI tract, metabolized in the liver, and excreted in the urine.

Phenobarbital Route #1

Route (Oral), Onset (30 to 60 minutes), Duration (10 to 16 hours)

Phenobarbital Route #2

Route (IM, subcutaneous), Onset (10 to 30 minutes), Duration (4 to 6 hours)

Phenobarbital Route #3

Route (IV), Onset (5 minutes), Duration (4 to 6 hours)

Contraindications for Phenobarbital

Hypersensitivity, congenital anomalies (pregnancy), coma, depression, psychoses.

Cautions for Phenobarbital

Impaired renal or liver function; Hepatic impairment.

Adverse Effects of Phenobarbital

Somnolence, insomnia, vertigo, nightmares, lethargy, nervousness, hallucinations, insomnia, anxiety, dizziness, bradycardia, hypotension, syncope, nausea, vomiting, constipation, diarrhea, hypoventilation, respiratory depression, tissue necrosis at injection site, withdrawal syndrome.

Clinically Important Drug-Drug Interaction for Phenobarbital

Limit CNS depressants; Decreased synthesis of vitamin K and D; Decreases effectiveness of warfarin.

Clonazepam (Klonopin)

Potentiates the effects of GABA, an inhibitory neurotransmitter, thereby stabilizing nerve cell membranes.

Therapeutic Actions of Clonazepam

Decreases excitability and hyperexcitability throughout the CNS by reducing conduction through nerve pathways.

Effects of Clonazepam

Reduces tonic-clonic, muscular, and emotional responses to stimulation.

Clonazepam

Provides muscle relaxation and anxiety relief without significantly affecting cortical (higher brain) functioning.

Indications of Clonazepam

Treatment of seizure disorders (particularly absence seizures, myoclonic seizures, and Lennox-Gastaut syndrome). Management of panic disorders and anxiety disorders (due to its anxiolytic and sedative effects).

Clonazepam Effectiveness

Clonazepam may lose its effectiveness within 3 months, and affected patients may respond to dose adjustment.

Clonazepam Pharmacokinetics - Absorption

Well absorbed from the gastrointestinal (GI) tract.

Clonazepam Pharmacokinetics - Metabolism

Metabolized in the liver.

Clonazepam Pharmacokinetics - Excretion

Excreted in the urine.

Clonazepam Half-life

Has a long half-life of 18 to 50 hours.

Clonazepam Formulation

Available as an orally disintegrating tablet, which is beneficial for patients who have difficulty swallowing pills.

Clonazepam Contraindications

Hypersensitivity, congenital anomalies (pregnancy), coma, depression, psychoses.

Clonazepam Cautions

Impaired renal or liver function, hepatic impairment.

Clonazepam Adverse Effects

Depression, confusion, drowsiness, lethargy, fatigue, constipation, dry mouth, anorexia, cardiac arrhythmias and changes in blood pressure, urinary retention, loss of libido, physical dependence, and withdrawal syndrome.

Clonazepam Drug-Drug Interaction

Avoid alcohol and CNS depressants.

Gabapentin (Neurontin) Therapeutic Actions

Exact mechanism of action is not understood; may bind to voltage-activated calcium channels; is structurally related to GABA, but does not affect GABA levels.

Gabapentin Indications

Treatment of focal onset seizures with and without secondary generalization, postherpetic neuralgia.

Gabapentin Pharmacokinetics

Is well absorbed from the GI tract and widely distributed in the body.

Gabapentin Contraindications

Hypersensitivity, severe hepatic dysfunction, congenital malformations, ventricular septal defects and oral clefts.

Gabapentin Cautions

Renal or hepatic dysfunction, renal stones.

Gabapentin Adverse Effects

Drowsiness, ataxia, dizziness, edema, fatigue, nystagmus, nausea, vomiting, hypersensitivity and angioedema, drug reaction with eosinophilia and systemic symptoms.

Gabapentin Drug-Drug Interaction

Avoid/limit alcohol and CNS depressants.

Carbidopa-levodopa Therapeutic Actions

Levodopa is a precursor of dopamine, which is deficient in parkinsonism; it crosses the blood-brain barrier, where it is converted to dopamine and acts as a replacement neurotransmitter.

Carbidopa-levodopa Indications

Treatment of parkinsonism and Parkinson's disease.

Carbidopa-levodopa Pharmacokinetics

Given orally and are generally well absorbed from the GI tract and widely distributed in the body. Metabolized in the liver and peripheral cells and excreted in the urine.

Carbidopa-levodopa Contraindications

Hypersensitivity and in angle-closure glaucoma.

Carbidopa-levodopa Cautions

Cardiovascular disease, including myocardial infarction, arrhythmias, and hypertension; bronchial asthma; history of peptic ulcers; urinary tract obstruction; and psychiatric disorders.

Carbidopa-levodopa Adverse Effects

Adventitious movements, ataxia, increased hand tremor, dizziness, numbness, weakness, agitation, anxiety, anorexia, nausea, vomiting, dry mouth, dysphagia, urinary retention, flushing, cardiac irregularities, psychosis.

Carbidopa-levodopa Drug-Drug Interaction

Avoid combining with monoamine oxidase inhibitors (MAOIs). Avoid iron salts or dopamine antagonists.

Diphenhydramine

An anticholinergic drug used for the treatment of parkinsonism and allergy symptoms.

Therapeutic Actions of Diphenhydramine

Treatment of parkinsonism, whether idiopathic, atherosclerotic, or postencephalitic, and for the relief of symptoms of extrapyramidal disorders.

Indications for Diphenhydramine

Adjunctive agent for treatment of Parkinson's disease; treatment of parkinsonism, including drug-induced disease particularly in older adults and in patients at the early stages of disease; also used to treat allergy symptoms and motion sickness.

Pharmacokinetics of Diphenhydramine

Absorbed from the GI tract, reaching peak levels in 1 to 4 hours. They are metabolized in the liver and excreted by cellular pathways.

Contraindications for Diphenhydramine

Hypersensitivity reactions, narrow-angle glaucoma, GI obstruction, genitourinary (GU) obstruction, prostatic hypertrophy, and myasthenia gravis.

Cautions for Diphenhydramine

Tachycardia, other dysrhythmias, and hypertension or hypotension.

Adverse Effects of Diphenhydramine

Slowed GI motility and secretions with dry mouth and constipation, urinary retention, blurred vision, and dilated pupils. Disorientation, confusion, memory loss, agitation, nervousness, delirium, dizziness, light-headedness, weakness, dry mouth, nausea, vomiting, paralytic ileus, and constipation related to decreased GI secretions and motility.

Drug-Drug Interaction with Diphenhydramine

Avoid combining tricyclic antidepressants and the phenothiazines, for there is a risk of paralytic ileus and psychoses.

Baclofen

A muscle relaxant that is a gamma-aminobutyric acid analogue, inhibiting monosynaptic and polysynaptic spinal reflexes.

Therapeutic Actions of Baclofen

Inhibits monosynaptic and polysynaptic spinal reflexes; CNS depressant.

Indications for Baclofen

Alleviation of signs and symptoms of spasticity; may be of use in spinal cord injuries or spinal cord diseases.

Pharmacokinetics of Baclofen (Oral)

Route: Oral, Onset: 1 hour, Peak: 2 hours, Duration: 4 to 8 hours.

Pharmacokinetics of Baclofen (Intrathecal)

Route: Intrathecal, Onset: 30 to 60 minutes, Peak: 4 hours, Duration: 4 to 8 hours.

Contraindications for Baclofen

Hypersensitivity reactions, and with skeletal muscle spasms resulting from rheumatic disorders.

Cautions for Baclofen

For those with a history of epilepsy, because the CNS depression and imbalance caused by these drugs may exacerbate the seizure disorder; with cardiac dysfunction, because muscle function may be depressed; with any condition marked by muscle weakness; and with hepatic or renal dysfunction.

Adverse Effects of Baclofen

Drowsiness, fatigue, weakness, confusion, headache, and insomnia. Gastrointestinal disturbances, including nausea, dry mouth, anorexia, and constipation.

Drug-Drug Interaction with Baclofen

If any of the centrally acting skeletal muscle relaxants are taken with other CNS depressants or alcohol, CNS depression may increase.

Cyclobenzaprine

A muscle relaxant that acts centrally within the CNS and interferes with reflexes that cause muscle spasm.

Spasmolytic

A substance that lyses or relieves skeletal muscle spasms.

GABA

Gamma-aminobutyric acid, possibly increased by cyclobenzaprine, enhancing inhibitory effects in the CNS.

Indications for Cyclobenzaprine

Relief of discomfort associated with acute, painful musculoskeletal conditions in adults; short term use (2-3 weeks).

Pharmacokinetics of Cyclobenzaprine

Available in a controlled release oral form for continual control of discomfort without repeated dosings.

Contraindications for Cyclobenzaprine

Hypersensitivity reactions and skeletal muscle spasms resulting from rheumatic disorders.

Cautions for Cyclobenzaprine

History of epilepsy, cardiac dysfunction, muscle weakness, hepatic or renal dysfunction.

Adverse Effects of Cyclobenzaprine

Drowsiness, fatigue, weakness, confusion, headache, insomnia, GI disturbances, hypotension, arrhythmias, urinary frequency, enuresis, and urinary urgency.

Clinically Important Drug-Drug Interaction

CNS depression may increase if taken with other CNS depressants or alcohol; patients should avoid alcohol.

Dantrolene

A skeletal muscle relaxant that interferes with the release of calcium from the sarcoplasmic reticulum within skeletal muscles.

Indications for Dantrolene

Control of clinical spasticity from upper motor neuron disorders; preoperatively to prevent malignant hyperthermia; IV for management of fulminant malignant hyperthermia.

Pharmacokinetics of Dantrolene

Available in oral or parenteral forms; slowly absorbed from the GI tract; half-life of 4 to 8 hours; excretion through urine.

Dantrolene Oral Route

1 Route (Oral), Onset (Slow), Peak (4 to 6 hours), Duration (8 to 10 hours).

Dantrolene IV Route

2 Route (IV), Onset (Rapid), Peak (5 hours), Duration (6 to 8 hours).

Contraindications for Dantrolene

Contraindicated in the presence of any known allergy to the drug to prevent hypersensitivity reactions.

Contraindications

Conditions where a drug should not be used due to potential harm.

Active hepatic disease

A condition that may interfere with the metabolism of the drug and is associated with known liver toxicity.

Lactation

The period of breastfeeding during which the drug may cross into human milk and cause adverse effects in the infant.

Cautions

Conditions that require careful consideration before using a drug due to potential risks.

History of liver disease

A past medical condition that may increase the risk of drug toxicity.

Adverse Effects

Unwanted side effects that may occur with drug use.

Drowsiness

A state of feeling sleepy or lethargic, which can be a side effect of the drug.

Hepatitis

Inflammation of the liver that can occur as an adverse effect.

Hepatocellular toxicity

Liver cell damage that can increase when combined with estrogens.

Botulinum toxins

A type of drug that can interact with neuromuscular junction blockers and other drugs, leading to additive effects.

Codeine

An opioid agonist used for pain relief and cough suppression.

Analgesia

Pain relief achieved by acting on opioid receptors in the CNS.

Sedation

A calming effect or drowsiness produced by the drug.

Antitussive Effect

The ability of the drug to suppress coughing.

Pharmacokinetics

The study of how a drug is absorbed, distributed, metabolized, and excreted.

IV administration

The fastest route to achieve therapeutic levels of a drug.

IM and subcutaneous administration

Routes of drug administration that result in slower absorption.

Gender differences in absorption

Absorption is generally slower in females due to higher fat content in muscles and tissue.

Distribution

The process by which a drug spreads throughout the body, including crossing the placenta.

Metabolism

The process by which the body breaks down a drug, primarily occurring in the liver.