Lack of Bioequivalence Among Low-dose, Enteric-coated Aspirin Preparations

Personalized Dual Antiplatelet Therapy in Acute Coronary Syndromes: Striking a Balance Between Bleeding and Thrombosis

PURPOSE OF REVIEW

Dual antiplatelet therapy (DAPT)-aspirin in conjunction with a P2Y12 inhibitor-is the cornerstone of managing patients with acute coronary syndromes post-revascularization, but the clinical response is highly variable, with potentially devastating consequences. Herein, we review the mechanisms underpinning said variability and explore emerging approaches to normalizing therapeutic benefit.

RECENT FINDINGS

The potent P2Y12 inhibitors, prasugrel and ticagrelor, exhibit minimal inter-individual variability, replacing clopidogrel in DAPT and achieving greater rates of therapeutic response. However, these benefits decline in later phases when bleeding risk begins to supersede that of ischemia. Guided de-escalation of P2Y12 inhibition as well as shortening DAPT duration have emerged as strategies that retain antithrombotic efficacy while reducing bleeding risk. Aspirin is the other component of DAPT but is also used in isolation for secondary prevention of thrombotic disease. In contrast to the P2Y12 inhibitors, genetic influences on aspirin non-response appear to be outweighed by a triad of clinical factors: non-adherence, enteric aspirin use, and inappropriate dosing according to bodyweight and BMI. Multiple de-escalation strategies for DAPT have been shown to mitigate bleeding risk, but it remains unclear which approach is ideal, necessitating head-to-head investigations to determine which exhibits the most favorable cost-to-benefit ratio. However, there is likely a role for more than one approach in clinical practice, depending on patient risk profile. Our approach to aspirin use is also in need of reassessment: strategies to improve adherence, avoidance of enteric aspirin in cardiac patients, and dose adjustment according to bodyweight and/or BMI are all likely to improve rates of therapeutic response. Moreover, platelet function testing may have a role in identifying patients expected to benefit from primary prophylactic aspirin.

Pharmacological Efficacy and Gastrointestinal Safety of Different Aspirin Formulations for Cardiovascular Prevention: A Narrative Review

Aspirin inhibits platelet function by irreversibly inhibiting the synthesis of thromboxane A2 (TxA2). Aspirin, at low doses, is widely used for cardiovascular prevention. Gastrointestinal discomfort, mucosal erosions/ulcerations and bleeding are frequent complications of chronic treatment. To reduce these adverse effects, different formulations of aspirin have been developed, including enteric-coated (EC) aspirin, the most widely used aspirin formulation. However, EC aspirin is less effective than plain aspirin in inhibiting TxA2 production, especially in subjects with high body weight. The inadequate pharmacological efficacy of EC aspirin is mirrored by lower protection from cardiovascular events in subjects weighing >70 kg. Endoscopic studies showed that EC aspirin causes fewer erosions of the gastric mucosa compared to plain aspirin (which is absorbed in the stomach) but causes mucosal erosions in the small intestine, where it is absorbed. Several studies demonstrated that EC aspirin does not reduce the incidence of clinically relevant gastrointestinal ulceration and bleeding. Similar results were found for buffered aspirin. Although interesting, the results of experiments on the phospholipid-aspirin complex PL2200 are still preliminary. Considering its favorable pharmacological profile, plain aspirin should be the preferred formulation to be used for cardiovascular prevention.

Pharmacokinetic and pharmacodynamic profiles of a novel phospholipid-aspirin complex liquid formulation and low dose enteric-coated aspirin: results from a prospective, randomized, crossover study

Low dose enteric-coated aspirin (EC-ASA) is routinely used for secondary cardiovascular event prevention. However, absorption of EC tablets is poor, which can result in subtherapeutic antiplatelet effects. Phospholipid-aspirin liquid filled capsules (PL-ASA) are a novel FDA-approved immediate-release formulation designed to reduce gastrointestinal (GI) injury by limiting direct contact with the stomach lining. We compared the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of PL-ASA versus EC-ASA at a low dose. This randomized, open-label, crossover study assessed PK and PD following a single 81-mg dose of PL-ASA versus EC-ASA under fasting conditions in 36 volunteers without cardiovascular disease between 18 and 75 years of age. Volunteers were randomly assigned 1:1 to either PL-ASA then EC-ASA or vice versa with a minimum 14-day washout. Assessments included PK parameters for acetylsalicylic acid and salicylic acid, platelet aggregation in response to arachidonic acid (AA), and serum thromboxane B2 (TxB₂) assessments over 24 h. PL-ASA was rapidly absorbed. PL-ASA reached T_max 3 h earlier (1.01 vs. 4.00 h, p < 0.0001), with almost double the C_max (720 vs. 368 ng/mL, p < 0.0001) and overall 44% higher exposure of acetylsalicylic acid (AUC_0-t: 601 vs. 416 h*ng/mL, p = 0.0013) compared with EC-ASA. Within 1 h of dosing, PL-ASA achieved significantly lower residual platelet aggregation, which persisted for the full 24 h (median AA-LTA was 47% with PL-ASA vs. 80.5% with EC-ASA; p = 0.0022 at hour-24). Treatment with PL-ASA also resulted in significantly lower serum TxB₂ concentrations at each time point compared with EC-ASA (all p-values < 0.05). PL-ASA resulted in faster and more complete aspirin absorption paralleled by more prompt and potent platelet inhibition compared with EC-ASA after a single 81 mg dose. PL-ASA represents an attractive novel aspirin formulation for the secondary prevention of cardiovascular events.

Clinical Trial Registration ClinicalTrials.gov identifier: NCT04811625.

Pharmacokinetic and Pharmacodynamic Profile of a Novel Phospholipid Aspirin Formulation

Aspirin is one of the most widely used medicines. Although aspirin is commonly utilized for the treatment of several medical conditions, its broadest uptake is for the prevention of recurrent ischemic events in patients with atherosclerotic disease. Its mechanism of action of inhibiting platelet activation via blockade of thromboxane A2 production is unique and is not covered by any other antiplatelet agents. While plain, uncoated, immediate-release aspirin is used in acute settings to help assure rapid absorption, enteric-coated aspirin formulations dominate current chronic use, particularly in North America, including for secondary prevention of cardiovascular events. The unmet needs with current aspirin formulations include a high risk of gastrointestinal (GI) adverse events with plain aspirin, which enteric-coated formulations are not able to overcome, and subject to erratic absorption leading to reduced drug bioavailability. These observations underscore the need for aspirin formulations with a more favorable safety and efficacy profile. Phospholipid-aspirin complex (PL-ASA) is a novel formulation designed to address these needs. It is associated with reduced local acute GI injury compared with plain aspirin, and predictable absorption resulting in more reliable platelet inhibition compared with enteric-coated tablets. This review explores the rationale and pharmacologic profile of PL-ASA intended to address the unmet needs for aspirin therapy.

No Difference Between Low- and Regular-dose Aspirin for Venous Thromboembolism Prophylaxis After THA

BACKGROUND

Aspirin is established as an effective prophylaxis for venous thromboembolism (VTE) after THA; however, there is no consensus as to whether low- or regular-dose aspirin is more effective at preventing VTE.

QUESTIONS/PURPOSES

(1) Is there a difference in the incidence of symptomatic VTE within 90 days of elective THA using low-dose aspirin compared with regular-dose aspirin? (2) Is there a difference in the risk of significant bleeding (gastrointestinal and wound bleeding) and mortality between low- and standard-dose aspirin within 90 days after surgery?

METHODS

We retrospectively evaluated 7488 patients in our database who underwent THA between September 2012 and December 2016. A total of 3936 (53%) patients received aspirin alone for VTE prophylaxis after THA. During the study period, aspirin was prescribed as a monotherapy for VTE prophylaxis after surgery in low-risk patients (no history of VTE, recent orthopaedic surgery, hypercoagulable state, history of cardiac arrhythmia requiring anticoagulation, or receiving anticoagulation for any other medical conditions before surgery). Patients were excluded if aspirin use was contraindicated because of peptic ulcer disease, intolerance, or other reasons. Patients received aspirin twice daily (BID) for 4 to 6 weeks after surgery and were grouped into two cohorts: a low-dose (81 mg BID) aspirin group (n = 1033) and a standard-dose (325 mg BID) aspirin group (n = 2903). The primary endpoint was symptomatic VTE (deep vein thrombosis [DVT] and pulmonary embolism [PE]). Secondary endpoints included significant bleeding (gastrointestinal [GI] and wound) and mortality. Exploratory univariate analyses were used to compare confounders between the study groups. Multivariate regression was used to control for confounding variables (including age, sex, body mass index, comorbidities, and surgeon) as we compared the study groups with respect to the proportion of patients who developed symptomatic VTE, bleeding (GI or wound), and mortality within 90 days of surgery.

RESULTS

The 90-day incidence of symptomatic VTE was 1.0% in the 325-mg group and 0.6% in the 81-mg group (p = 0.35). Symptomatic DVT incidence was 0.8% in the 325-mg group and 0.5% in the 81-mg group (p = 0.49), and the incidence of symptomatic PE was 0.3% in the 325-mg group and 0.2% in the 81-mg group (p = 0.45). Furthermore, bleeding was observed in 0.8% of the 325-mg group and 0.5% of the 81-mg group (p = 0.75), and 90-day mortality was not different (0.1%) between the groups (p = 0.75). After accounting for confounders, regression analyses showed no difference between aspirin doses and the 90-day incidence of symptomatic VTE (odds ratio [OR], 0.90; 95% confidence interval [CI], 0.29-2.85; p = 0.85) or symptomatic DVT (OR, 0.96; 95% CI, 0.26-3.59; p = 0.95).

CONCLUSIONS

We found no difference in the incidence of symptomatic VTE after THA with low-dose compared with standard-dose aspirin. In the absence of compelling evidence to the contrary, low-dose aspirin appears to be a reasonable option for VTE prophylaxis in otherwise healthy patients undergoing elective THA.

LEVEL OF EVIDENCE

Level III, therapeutic study.