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# Ticagrelor
## Overview
Ticagrelor is a reversible, non-thienopyridine P2Y12 receptor antagonist that inhibits platelet activation and aggregation. Unlike clopidogrel, it does not require metabolic activation.
## Primary Indications
* Acute coronary syndrome (ACS): Unstable angina, non-ST-elevation myocardial infarction (NSTEMI), and ST-elevation myocardial infarction (STEMI).
* History of myocardial infarction (secondary prevention of high-risk patients).
* Coronary artery disease (off-label/specific trial protocols for high-risk CAD).
## Adult Dosing
* **Loading Dose:** 180 mg orally once.
* **Maintenance Dose:** 90 mg orally twice daily. After 12 months in post-MI patients, may decrease to 60 mg twice daily.
* **Maximum Dose:** 90 mg BID (higher doses increase bleeding risk with no efficacy benefit).
## Pediatric Dosing
Safety and efficacy have not been established in pediatric patients under 18 years. Use is generally avoided in pediatrics.
## Dose Adjustments
* **Renal Impairment:** No dose adjustment necessary.
* **Hepatic Impairment:** Avoid in patients with severe hepatic impairment; use with caution in moderate impairment.
* **ASA Limitation:** When used with aspirin, the maintenance dose of aspirin should not exceed 100 mg daily. Higher aspirin doses reduce the efficacy of ticagrelor.
## Contraindications
* Active pathological bleeding (e.g., peptic ulcer, intracranial hemorrhage).
* History of intracranial hemorrhage.
* Severe hepatic impairment.
* Known hypersensitivity to ticagrelor.
## Adverse Effects
* **Bleeding:** Major and minor bleeding (epistaxis, GI bleed, bruising).
* **Dyspnea:** Very common (approx. 14%); usually mild-to-moderate and often transient.
* **Bradyarrhythmia:** Risk of ventricular pauses (mostly in the first week of treatment).
* **Hyperuricemia:** Potential for increased serum uric acid levels.
## Key Drug Interactions
* **CYP3A4 Inhibitors:** (e.g., ketoconazole, clarithromycin, ritonavir) May increase ticagrelor levels; avoid concurrent use.
* **CYP3A4 Inducers:** (e.g., rifampin, phenytoin, carbamazepine) May decrease ticagrelor efficacy; avoid concurrent use.
* **Anticoagulants/NSAIDs:** Significantly increase the risk of major bleeding.
* **Statins:** May increase simvastatin or lovastatin levels; limit simvastatin dose to 40 mg daily.
## Monitoring
* Baseline and periodic hemoglobin/hematocrit.
* Signs and symptoms of bleeding (e.g., melena, hematuria, easy bruising).
* Presence of dyspnea.
* Adherence (twice-daily dosing is prone to non-adherence compared to once-daily antiplatelets).
## Clinical Pearls
* **Reversibility:** Unlike clopidogrel and prasugrel, ticagrelor's effect is reversible; platelet function typically recovers within 3–5 days after discontinuation.
* **Surgery:** Discontinue at least 5 days before elective surgery to minimize bleeding risk.
* **Dyspnea Management:** Counsel patients that dyspnea is a known side effect and rarely necessitates drug discontinuation unless it becomes severe or persistent.
* **Aspirin Interaction:** The "Aspirin effect" is a paradoxical finding; maintenance doses of aspirin >100 mg reduce the antiplatelet efficacy of ticagrelor.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice protocols vary by institution. Always verify current prescribing information, package inserts, and local clinical guidelines before administering medication.
