Key Medications: Uses, Mechanisms, and Side Effects
Phenytoin
Definition
Phenytoin is an anticonvulsant used to control seizures in epilepsy.
Mechanism of Action (MOA)
Phenytoin works by stabilizing neuronal membranes and reducing the spread of seizure activity through the brain by inhibiting voltage-gated sodium channels.
Uses
- Generalized tonic-clonic seizures
- Partial seizures
- Status epilepticus
Adverse Drug Reactions (ADR)
Common side effects include gingival hyperplasia, ataxia, dizziness, and rash. Severe reactions may include blood dyscrasias, hepatotoxicity, and teratogenicity (fetal harm in pregnancy).
Pilocarpine
Definition
Pilocarpine is a muscarinic agonist used primarily for its parasympathomimetic effects.
MOA
Pilocarpine stimulates muscarinic receptors, increasing acetylcholine activity in the parasympathetic nervous system, leading to pupil constriction (miosis) and increased aqueous humor outflow in the eye.
Uses
- Glaucoma treatment
- Sialogogue in xerostomia (dry mouth)
ADR
Side effects include blurred vision, excessive salivation, sweating, and bradycardia. It can also cause eye irritation and headaches.
Etoricoxib
Definition
Etoricoxib is a selective COX-2 inhibitor, a type of nonsteroidal anti-inflammatory drug (NSAID).
MOA
It selectively inhibits COX-2, an enzyme involved in the production of prostaglandins, reducing inflammation, pain, and fever, while sparing COX-1 and thus minimizing gastrointestinal side effects.
Uses
- Osteoarthritis
- Rheumatoid arthritis
- Acute gout
- Ankylosing spondylitis
ADR
Common side effects include hypertension, peripheral edema, gastrointestinal issues, and increased risk of cardiovascular events such as myocardial infarction and stroke.
Morphine
Definition
Morphine is a potent opioid analgesic used to manage moderate to severe pain.
MOA
Morphine acts primarily on opioid receptors (mu-receptors) in the brain and spinal cord, inhibiting pain transmission and perception by altering the pain response pathway.
Uses
- Acute pain management
- Chronic pain management
- Palliative care for end-stage cancer or severe heart failure
ADR
Common adverse effects include respiratory depression, constipation, nausea, vomiting, sedation, and risk of dependence and addiction.
Dopamine
Definition
Dopamine is a catecholamine neurotransmitter and vasopressor used to treat shock and low blood pressure.
MOA
At low doses, dopamine stimulates D1 receptors, causing vasodilation and increased renal blood flow. At moderate doses, it stimulates beta-1 adrenergic receptors, increasing heart rate and contractility.