Usage
- Aspirin + Dipyridamole is prescribed to reduce the risk of stroke in patients who have experienced a transient ischemic attack (TIA or “mini-stroke”) or ischemic stroke due to thrombosis (blood clot).
- Pharmacological Classification: Antiplatelet agent.
- Mechanism of Action: This combination medication works by inhibiting platelet aggregation, thus reducing the formation of blood clots. Aspirin inhibits cyclooxygenase, an enzyme involved in thromboxane A2 synthesis (a potent platelet aggregator and vasoconstrictor). Dipyridamole inhibits phosphodiesterase, increasing cyclic AMP levels and further reducing platelet aggregation, also having vasodilatory properties.
Alternate Names
- Aspirin and Extended-Release Dipyridamole
- Brand Names: Aggrenox
How It Works
- Pharmacodynamics: Aspirin irreversibly inhibits cyclooxygenase-1 (COX-1) in platelets, reducing thromboxane A2 production and inhibiting platelet aggregation. Dipyridamole inhibits phosphodiesterase and adenosine uptake, increasing cyclic AMP levels and adenosine concentrations, which reduces platelet adhesion and promotes vasodilation. The combination provides a synergistic antiplatelet effect.
- Pharmacokinetics: Aspirin is readily absorbed from the gastrointestinal tract, rapidly hydrolyzed to salicylic acid in the liver, and then metabolized to various conjugates. Dipyridamole is absorbed from the gastrointestinal tract. The extended-release formulation provides a sustained plasma concentration over time. Dipyridamole is extensively metabolized in the liver, primarily via glucuronidation. Both drugs are primarily excreted in the urine as metabolites. The elimination pathways for both drugs are primarily renal.
- Mode of Action: Aspirin’s action on COX-1 in platelets and Dipyridamole’s effect on phosphodiesterase and adenosine uptake are the primary mechanisms contributing to the synergistic inhibition of platelet aggregation.
Dosage
Standard Dosage
Adults:
- One capsule (containing 25 mg aspirin and 200 mg extended-release dipyridamole) twice daily, one in the morning and one in the evening. Swallow capsules whole.
Children:
- Use is not recommended in children and adolescents due to the risk of Reye’s syndrome associated with aspirin use in viral infections.
Special Cases:
- Elderly Patients: No specific dose adjustments are required based solely on age. Monitor for bleeding.
- Patients with Renal Impairment: Use with caution. Not recommended with GFR < 10ml/min.
- Patients with Hepatic Dysfunction: Use with caution. Dosage modifications may be necessary depending on the severity.
- Patients with Comorbid Conditions: Exercise caution in patients with a history of bleeding disorders, peptic ulcers, asthma, or those consuming three or more alcoholic drinks daily.
Clinical Use Cases
The primary use of aspirin + dipyridamole is for secondary stroke prevention after TIA or ischemic stroke. It is not typically indicated for use during procedures like intubation, surgical procedures, or in the ICU or emergency settings as a primary intervention, although patients may continue taking it during these periods.
Dosage Adjustments
Dose adjustments should be considered in patients with renal or hepatic dysfunction, as discussed above. If severe headaches occur initially, consider switching to one capsule at bedtime and low-dose aspirin in the morning; then revert to the standard regimen as soon as possible.
Side Effects
Common Side Effects
- Headache
- Dizziness
- Gastrointestinal upset (nausea, vomiting, diarrhea, dyspepsia)
Rare but Serious Side Effects
- Bleeding (gastrointestinal, intracranial)
- Allergic reactions
Long-Term Effects
Chronic use of aspirin + dipyridamole may increase the risk of gastrointestinal bleeding.
Adverse Drug Reactions (ADR)
- Severe bleeding (hematemesis, melena, hematuria)
- Anaphylaxis
Contraindications
- Hypersensitivity to aspirin, dipyridamole, or any other NSAIDs.
- Active bleeding or significant risk of bleeding (e.g., recent surgery, peptic ulcer disease).
- Late pregnancy (after 20 weeks).
- Asthma with nasal polyps.
- Severe renal impairment (GFR <10 ml/min).
Drug Interactions
- Anticoagulants (warfarin, heparin)
- NSAIDs (ibuprofen, naproxen): Increased risk of bleeding.
- Antiplatelet agents (clopidogrel): Increased risk of bleeding.
- ACE inhibitors, ARBs: Increased risk of renal impairment.
- Methotrexate: Increased methotrexate toxicity.
- Alcohol: Increased risk of gastrointestinal bleeding.
Pregnancy and Breastfeeding
- Pregnancy: Avoid use after 20 weeks of gestation due to the risk of premature closure of the ductus arteriosus and other fetal complications.
- Breastfeeding: Aspirin and dipyridamole are excreted in breast milk. Use cautiously. Consider the risk to the infant of exposure versus the benefit to the mother.
Drug Profile Summary
- Mechanism of Action: Inhibits platelet aggregation.
- Side Effects: Headache, dizziness, GI upset, bleeding.
- Contraindications: Hypersensitivity, active bleeding, late pregnancy, asthma with nasal polyps.
- Drug Interactions: Anticoagulants, NSAIDs, antiplatelet agents.
- Pregnancy & Breastfeeding: Avoid in late pregnancy. Use cautiously during breastfeeding.
- Dosage: One capsule twice daily.
- Monitoring Parameters: Signs of bleeding.
Popular Combinations
While aspirin is often used in low doses with this combination, avoid additional aspirin or NSAIDS unless directed by a physician.
Precautions
- Assess for bleeding risk before initiating therapy.
- Monitor for signs and symptoms of bleeding.
- Patients should inform their healthcare providers about all medications, supplements, and herbal products they are taking.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Aspirin + Dipyridamole?
A: One capsule (25 mg aspirin/200 mg extended-release dipyridamole) twice daily.
Q2: Can Aspirin + Dipyridamole be used in children?
A: No, it’s not recommended due to the risk of Reye’s syndrome.
Q3: What are the common side effects?
A: Headache, dizziness, and gastrointestinal upset are common.
Q4: What are the serious side effects?
A: Bleeding and allergic reactions are potentially serious side effects.
Q5: What are the contraindications for this medication?
A: Hypersensitivity, active bleeding, late pregnancy, and asthma with nasal polyps.
Q6: Can this medication be taken with other blood thinners?
A: Caution should be used when combining with other anticoagulants or antiplatelet agents. Consult a physician before combining such medications.
Q7: What should I do if I miss a dose?
A: Skip the missed dose and continue with your regular schedule. Do not double the dose.
Q8: Can this medicine be crushed or chewed?
A: No, the capsules should be swallowed whole.
Q9: Are there any dietary restrictions while taking this medication?
A: While no specific dietary restrictions are required, limit alcohol intake.
Q10: How should this medication be stored?
A: Store at room temperature in a closed container, away from moisture and heat.
