Pharmacology and Drug Classifications Review

Anticholinergic Drugs: Mechanism and Systemic Effects

  • Definition and Mechanical Action: Anticholinergic drugs act by occupying receptor sites, which effectively blocks acetylcholine (the primary neurotransmitter for cholinergic systems).

  • Cholinergic Baseline: Normal cholinergic activity is associated with "wet" functions (secretions) and muscle contraction.

  • Cardiovascular System:

    • Large doses of anticholinergics can increase the heart rate.

    • Small doses can paradoxically decrease the heart rate.

  • Gastrointestinal (GI) Tract:

    • Relaxes the smooth muscle tone of the GI tract.

    • Decreases GI motility and peristalsis.

    • Reduces gastric and intestinal secretions.

  • Urinary Tract:

    • Relaxes the bladder detrusor muscle.

    • Increases constriction of the internal sphincter.

    • A primary result of these actions is urinary retention.

  • Ocular Effects:

    • Causes dilated pupils.

    • Paralyzes ciliary muscles, which leads to a decrease in accommodation.

  • Glandular Secretions: Decreases salivation, perspiration, and bronchial secretions.

  • Bronchial Effects: Results in dilated bronchi and decreased bronchial secretions.

  • Central Nervous System (CNS):

    • Tremors and muscle rigidity are decreased.

    • Large doses can result in drowsiness, disorientation, and hallucinations.

  • Therapeutic Uses: Used for treating conditions such as motion sickness (e.g., Scopolamine acting on the CNS).

  • Contraindications: These drugs should not be used in patients with glaucoma, tachycardia, or myasthenia gravis.

  • Side Effects: Side effects include urinary retention, decreased sweat and saliva (dry mouth), dry eyes, and decreased muscle rigidity.

Benzodiazepines and Sedative-Hypnotics

  • Lorazepam:

    • Classified as a benzodiazepine, which functions by "slowing the brain."

    • Used as a seizure anti-anxiety agent and a sedative-hypnotic agent.

    • Side Effects: Tolerance, drowsiness, dizziness, hypotension, blurred vision, and memory impairment.

  • Benzodiazepine Overdose Protocol: The specific antagonist used for benzodiazepine overdose is Flumazenil.

Muscle Relaxants and Neuromuscular Disorders

  • General Action: Muscle relaxants relieve muscular spasm and pain associated with traumatic injury and spasticity from chronic debilitating disorders.

  • Categories of Action:

    • Centrally Acting: Relieves muscle spasms and spasticity while producing a sedative effect. Examples include Cyclobenzaprine (Central Acting), Baclofen, Tizanidine, Carisoprodol, Chlorzoxazone, and Methocarbamol.

    • Direct Acting: Decreases muscle spasm pain, increases range of motion, and suppresses hyperactive reflexes.

  • Specific Drug: Cyclobenzaprine:

    • Use: Relieves muscle spasms.

    • Side Effects: Blurred vision, dry mouth, THR (Tachycardia/Heart Rate increase), urinary retention, drowsiness, dizziness, headache, nervousness, confusion, and GI distress.

  • Nursing Assessment: Always note whether the patient has a history of narrow-angle glaucoma.

  • Nursing Interventions:

    • Monitor serum liver enzyme levels.

    • Observe for CNS side effects.

    • Do not stop the medication abruptly; it must be tapered off over a period of 11 week.

    • Avoid alcohol and other CNS depressants.

    • Usually prescribed for no longer than 33 weeks.

  • Multiple Sclerosis (MS): A neuromuscular autoimmune disorder that attacks the myelin sheath of nerve fibers in the brain and spinal cord, resulting in lesions known as plaques.

Anticonvulsant and Parkinson’s Medications

  • Phenytoin (Dilantin):

    • Action: Used for the treatment and prevention of tonic-clonic seizures and complex partial seizures.

    • Dosing: 20mg do not exceeds 50 mg then in 10 mins may give 5-10mg as a single dose if needed to control seizures

    • Therapeutic Serum Level: Recommended range is 10−20 mcg/mL10-20\,\text{mcg/mL}.

    • Contraindications: Pregnancy (seizures can become more frequent due to increased metabolic rates).

    • Side Effects: Gingival hyperplasia, nystagmus, diplopia, headache, dizziness, slurred speech, drowsiness, confusion, constipation, purple glove syndrome, V-Fib (Ventricular Fibrillation), and depression.

  • Valproic Acid:

    • Use: Prescribed for tonic-clonic, absence, and partial seizures.

    • Therapeutic Levels: Recommended range is 60−100 mcg/mL60-100\,\text{mcg/mL}.

    • Metabolism: Metabolized through the liver; caution is required in patients with liver disorders to avoid toxicity.

    • Side Effects: Dizziness, drowsiness, weakness, diplopia, insomnia, and anorexia.

  • Neostigmine:

    • Timing: Must be administered within 30 min30\,\text{min} to prevent a relapse of symptoms.

    • Administration: Give 30 min30\,\text{min} before eating to "open the throat" to prevent dysphagia and aspiration.

    • Stomach Environment: The stomach is at its most acidic right before eating or when emptying.

  • Carbidopa & Levodopa:

    • Carbidopa: Functions to keep dopamine from breaking down before reaching the brain.

    • Levodopa: Functions to produce dopamine.

    • Goal: To allow more dopamine to successfully cross the blood-brain barrier (BBB).

  • Benztropine Side Effects: As an anticholinergic, effects include THR, psychosis, heat stroke, constipation, urinary retention, drowsiness, dizziness, sedation, and decreased stomach peristalsis.

Pharmacokinetics and Drug Administration

  • Bioavailability: The percentage of an administered drug that is available for activity.

    • Example: Intravenous (IV) administration provides 100%100\% bioavailability.

  • Protein Binding: Drugs that are more than 90%90\% bound to protein are considered inactive.

    • Toxicity Risk: If two highly protein-bound drugs (e.g., Warfarin and Furosemide) are administered, they can compete for sites and lead to drug toxicity.

  • Half-Life: Represents the time it takes for the concentration of the drug to reduce by half.

    • Numerical Example: 50→25→12.5→76.7550 \rightarrow 25 \rightarrow 12.5 \rightarrow 76.75

  • Enteric Coated Tablets:

    • Must be swallowed whole to maintain therapeutic levels and ensure the drug is released gradually.

    • If crushed, the initial excessive drug release causes a risk of toxicity and can lead to potential fatal overdosing.

    • Crushing also increases the rate of absorption and causes oropharyngeal irritation.

  • Pediatric Medications:

    • Weight loss medication is typically indicated for age 1212 and older.

    • Pediatric oral doses are given through a syringe into the buccal (cheek) area.

    • For injections in infants/children, use the vastus lateralis as it is the most muscular ("meatiest") part.

  • Rights of Medication Administration:

    1. Right Patient

    2. Right Dose

    3. Right Drug

    4. Right Route

    5. Right Time

    6. Right Documentation

    • If any of these criteria are missing from an order, the pharmacist or doctor must be called.

  • NPO (Nothing by Mouth): If a patient is NPO, oral medication can be held and given via IV if needed.

  • Geriatric Considerations:

    • Older people taking multiple medications are at higher risk for liver and kidney toxicity.

    • Polypharmacy: Defined as taking more than 66 medications at one time.

Drug Development and Clinical Phases

  • Generic Name: The official nonproprietary name for a drug; not owned by any company, written in lowercase letters, and generally less expensive.

  • Phase I: Drug or treatment is given in a large group of people for the first time.

  • Phase II: Drug or treatment is given to a larger group to determine effectiveness.

  • Phase III: Drug or treatment is given to large groups of people to confirm effectiveness and monitor side effects.

  • Phase IV: Studies conducted after the drug or treatment has been marketed to gather information on the drug's effect in various populations and assess side effects with long-term use.

  • Controlled Substances: Must be locked away at all times, and a second nurse must witness and sign off on their use.

Respiratory and Serum Values

  • Spacer Inhaler: Easier for children to use to ensure they receive the full dose of medication.

    • Nursing Education: Ensure the patient rinses their mouth after use.

  • Sodium (Na⁺): Normal serum range is 135−145 mEq/dL135-145 \text{ mEq/dL}.

  • Hyponatremia: Low sodium side effects may include:

    • Headache

    • Confusion

    • Muscle weakness

    • Seizures

    • Coma

  • Hypernatremia: High sodium side effects may include:

    • Thirst

    • Dry mouth

    • Fatigue

    • Restlessness

    • Muscle twitching

    • Confusion or irritability

    • Seizures