Drug Guide
Aspirin, Methocarbamol
Classification
Therapeutic: Analgesic, Anti-inflammatory, Skeletal Muscle Relaxant
Pharmacological: Non-steroidal Anti-inflammatory Drug (NSAID), Muscle Relaxant
FDA Approved Indications
- Pain relief (mild to moderate pain)
- Inflammation reduction
- Muscle spasms associated with musculoskeletal conditions
Mechanism of Action
Aspirin inhibits cyclooxygenase enzymes (COX-1 and COX-2), reducing prostaglandin synthesis, leading to analgesic, anti-inflammatory, and antipyretic effects. Methocarbamol depresses neuronal activity in the brain and spinal cord, producing skeletal muscle relaxation.
Dosage and Administration
Adult: Aspirin: 325-650 mg every 4-6 hours as needed. Methocarbamol: 1500 mg four times daily for muscle spasms.
Pediatric: Use is limited; consult specific guidelines and physician.
Geriatric: Dose adjustment may be necessary due to increased sensitivity and comorbidities.
Renal Impairment: Adjust dose appropriately; monitor renal function.
Hepatic Impairment: Use with caution; no specific adjustment specified.
Pharmacokinetics
Absorption: Well absorbed from the gastrointestinal tract.
Distribution: Widely distributed; crosses the placental barrier, and enters breast milk.
Metabolism: Aspirin is hydrolyzed to salicylic acid; Methocarbamol is metabolized in the liver.
Excretion: Primarily via renal excretion of metabolites.
Half Life: Aspirin: approximately 15-20 minutes (acetylsalicylic acid); Salicylic acid: 2-3 hours; Methocarbamol: approximately 1-2 hours.
Contraindications
- Hypersensitivity to aspirin or methocarbamol
- History of salicylate sensitivity or bleeding disorders.
- Children and teenagers with viral infections (risk of Reye's syndrome).
Precautions
- Use with caution in peptic ulcer, bleeding disorders, asthma, renal or hepatic impairment.
Adverse Reactions - Common
- Gastrointestinal upset (Common)
- Drowsiness, dizziness (Common)
Adverse Reactions - Serious
- Gastrointestinal bleeding (Less common)
- Allergic reactions including rash, bronchospasm (Rare)
- Reye's syndrome in children (Serious, contraindicated in children with viral infections.)
Drug-Drug Interactions
- Anticoagulants (increased bleeding risk)
- Other NSAIDs (potentiation of effects)
- Corticosteroids
Drug-Food Interactions
- Alcohol (increased gastrointestinal bleeding risk)
Drug-Herb Interactions
- Ginger, Ginkgo (may increase bleeding risk)
Nursing Implications
Assessment: Monitor for signs of bleeding, gastrointestinal discomfort, allergic reactions, and CNS effects.
Diagnoses:
- Risk for bleeding
- Impaired comfort related to pain or adverse effects
Implementation: Administer with food or milk to minimize gastrointestinal irritation. Monitor renal function and complete blood count as needed.
Evaluation: Assess pain relief, inflammation reduction, and monitor for adverse effects.
Patient/Family Teaching
- Do not take aspirin with other NSAIDs or blood thinners without consulting a healthcare provider.
- Report any unusual bleeding, rash, or allergic symptoms.
- Avoid alcohol during therapy.
- Take methocarbamol exactly as prescribed for muscle spasms.
Special Considerations
Black Box Warnings:
- Reyes' syndrome risk in children and teenagers with viral infections.
- Gastrointestinal bleeding risk.
Genetic Factors: Variability in aspirin metabolism may affect efficacy and safety.
Lab Test Interference: Aspirin may affect bleeding time and platelet function tests.
Overdose Management
Signs/Symptoms: Tinnitus, high fever, dehydration, metabolic acidosis, coma.
Treatment: Supportive care, activated charcoal, alkalization of urine, alkalization therapy, hemodialysis in severe cases.
Storage and Handling
Storage: Store at room temperature away from moisture and light.
Stability: Stable under recommended storage conditions.