Aspirin for myocardial infarction. Clinical pharmacokinetic considerations

Morphine Interaction with Aspirin: a Double-Blind, Crossover Trial in Healthy Volunteers

Aspirin is a cornerstone in the antiplatelet therapy for acute coronary syndromes. Coadministration of morphine may potentially influence the intestinal absorption, pharmacokinetics, and pharmacodynamics, as seen with P2Y₁₂ inhibitors. In this trial, healthy volunteers were randomized to receive morphine (5 mg, i.v. bolus injection) at one of seven different time points before, after, or with aspirin (162 mg, p.o.) in a double-blind, placebo-controlled fashion. After a 14-day washout, subjects received placebo instead of morphine. Pharmacokinetics were determined by liquid chromatography, and aspirin's effects were measured by platelet function tests (whole-blood platelet aggregation: multiplate, platelet plug formation: PFA-100). Morphine increased the total acetylsalicylic acid exposure by 20% compared with placebo when given simultaneously with aspirin, whereas C_max and t_max were not altered. Morphine had no significant effect on aspirin-induced platelet inhibition. In contrast to coadministration with P2Y₁₂ inhibitors, morphine appears to have negligible interaction with aspirin.

Morphine decreases ticagrelor concentrations but not its antiplatelet effects: a randomized trial in healthy volunteers

BACKGROUND

Our recent drug interaction trial with clopidogrel shows that morphine decreases the concentrations and pharmacodynamic effects of clopidogrel, which could lead to treatment failure in susceptible individuals. We hypothesized that the pharmacodynamic consequences of drug-drug interactions would be less between morphine and ticagrelor.

MATERIALS AND METHODS

Twenty-four healthy subjects received a loading dose of 180 mg ticagrelor together with placebo or 5 mg morphine intravenously in a randomized, double-blind, placebo-controlled, crossover trial. Pharmacokinetics were determined by liquid chromatography tandem mass spectrometry, and ticagrelor pharmacodynamic effects were measured by platelet function tests (whole blood platelet aggregation: multiplate, platelet plug formation: PFA-100, vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay).

RESULTS

Concomitant i.v. injection of morphine slows drug resorption of ticagrelor and its active metabolite (P < 0·05) by 1 h and decreases plasma levels of ticagrelor and its active metabolite by 25-31% (P ≤ 0·03) and the drug exposure (area under the curve) by 22-23% (P ≤ 0·01). Importantly, however, the pharmacodynamic effects of ticagrelor on platelet aggregation in whole blood, platelet plug formation and VASP phosphorylation are not affected by morphine.

CONCLUSIONS

Morphine co-administration moderately decreases ticagrelor plasma concentrations but does not inhibit its pharmacodynamic effects in healthy volunteers within 6 h after drug administration. Limitations of our trial include the investigation in healthy volunteers under standardized conditions, which does not necessarily reflect a realistic emergency scenario.

Morphine interaction with prasugrel: a double-blind, cross-over trial in healthy volunteers

Background

Morphine decreases the concentrations and effects of clopidogrel, which could lead to treatment failure in myocardial infarction.

Objectives

To clarify whether more potent P2Y₁₂-inhibitors may provide an effective alternative, we examined drug–drug interactions between morphine and prasugrel.

Methods

Twelve healthy volunteers received 60 mg prasugrel with placebo or 5 mg morphine intravenously in a randomized, double-blind, placebo-controlled, cross-over trial. Pharmacokinetics were determined by liquid chromatography tandem mass spectrometry, and prasugrel effects were measured by platelet function tests.

Results

Morphine neither diminished total drug exposure (AUC), which was the primary endpoint, nor significantly delayed drug absorption of prasugrel. However, morphine reduced maximal plasma concentrations (C_max) of prasugrel active metabolite by 31 % (p = 0.019). Morphine slightly, but not significantly, delayed the onset of maximal inhibition of platelet plug formation under high shear rates (30 vs. 20 min). Whole blood aggregation was not influenced.

Conclusions

Although morphine significantly decreases the maximal plasma concentrations of prasugrel active metabolite, it does not diminish its effects on platelets to a clinically relevant degree in healthy volunteers. However, it should be considered that the observed decrease in C_max of prasugrel active metabolite caused by morphine co-administration may gain relevance in STEMI patients.

Clinical Trial Registration: NCT01369186, EUDRA-CT#: 2010-023761-22.

Absorption kinetics of low-dose chewable aspirin--implications for acute coronary syndromes

BACKGROUND

This study describes the implications of the pharmacokinetics of low-dose chewable aspirin for acute coronary syndromes. Current guidelines recommend the administration of 162-325 mg aspirin chewing tablets for the treatment of acute myocardial infarction. Although aspirin is widely used and a cornerstone in myocardial infarction, there is no information available on the pharmacokinetics of low doses of chewable aspirin.

MATERIALS AND METHODS

This prospective trial assessed the pharmacokinetics of acetylsalicylic acid and its metabolite salicylic acid after intake of 162 mg chewable low-dose aspirin in 35 healthy volunteers. Plasma drug and metabolite levels were analysed using high-performance liquid chromatography, and corresponding pharmacodynamics were determined by impedance aggregometry.

RESULTS

Acetylsalicylic acid was rapidly absorbed with a mean Tmax of 27 ± 8 min. Tmax of salicylic acid was 69 ± 21 min. Mean Cmax was 1·8 ± 0·6 mg/L and 7·6 ± 1·4 for acetylsalicylic acid and salicylic acid, respectively. Arachidonic acid-induced aggregation showed maximum platelet inhibition 30 min after drug ingestion.

CONCLUSIONS

The characterization of the plasma-time profile fills the gap between the lack of data on pharmacokinetics and the pharmacodynamics and the recommendation for using low-dose chewable aspirin for acute coronary syndromes. We describe for the first time that a 162-mg dose of chewable aspirin is rapidly absorbed and achieves plasma concentrations of the active metabolite salicylic acid required to maximally inhibit platelet aggregation. However, a 162-mg dose is truly a minimum, and doubling this dose might be better for patients with myocardial infarction.

Excretion and ecotoxicity of pharmaceutical and personal care products in the environment

The presence and fate of pharmaceutical and personal care products (PPCPs) in the environment is undergoing increasing scrutiny. The existing clinical pharmacokinetics and pharmacodynamics data for 81 common compounds were examined for cues of ecotoxicity. Of these the proportions excreted were available for 60 compounds (i.e., 74%). The compounds had a low (< or =0.5%), a moderately low (6-39%), a relatively high (40-69%), or a high (> or =70%) proportion of the parent compound excreted. More than half of the compounds evaluated have low or moderately low proportions of the parent compound excreted. However, the proportions excreted were negatively but moderately correlated (r = -0.50; n = 13; P = 0.08) with the concentrations of the compounds in the aquatic environment, suggesting that the compounds that have low proportions excreted may also have inherently low degradability in the environment. Solubility, logK(ow), and pKa work well in predicting the behavior of PPCPs under clinical conditions and have been used in the environmental assessment of PPCPs prior to approval. However, these parameters did not correlate with the proportion of PPCPs excreted in the environment or their concentration in the environment, underscoring the need for research into the behavior of PPCPs in the environment. PPCPs occur in low concentrations in the environment and are unlikely to elicit acute toxicity. An ecotoxicity potential that is based on chronic toxicity, bioavailability, and duration of exposure to nontarget organisms is described as a guide in assessing the potency of these compounds in the environment.

[Pharmacology of aspirin]

Aspirin (acetylsalicylic acid) is the best-known salicylate and belongs to the non steroid anti-inflammatory drug class. Despite wide use being made since more than 100 years, knowledge about mechanism of action and therapeutic issues continually evolves. The main mechanism of action is prostaglandin synthesis inhibition. This is achieved through inhibition of prostaglandin endoperoxide synthase (PGHS) or cyclooxygenase (COX) synthesis. Most of the therapeutic uses of aspirin are explained by this mechanism. Nevertheless aspirin uses change as time goes by: if the main one during the first fifty years was an analgesic, anti-pyretic and anti-inflammatory one, the last fifty years saw aspirin being used mainly as an anti-thrombotic agent, in primary and secondary thrombo-embolic prevention. Better knowledge of mechanism of action points today at, on one hand, more selective and therefore better tolerated molecules, and, on the other hand, at new therapeutic applications, such as anti-cancer and neurodegenerative diseases prevention.

Open questions on bioequivalence: some problems and some solutions

This paper focuses on some specific situations where bioequivalence requires careful attention and tailored protocols in order to overcome intrinsic difficulties either marginally covered or fully neglected by operating guidelines. Some problems congregate with serious difficulties, namely high variability, very poorly absorbed drugs and endogenous substances with their own baseline. With endogenous substances, the dilemma faced is whether to subtract baseline from post-dose values in assessing bioequivalence. Either approach has intrinsic problems and is somewhat puzzling. In an attempt to resolve other existing problems, the most appropriate approach should be selected on a case-by-case basis, ensuring that the adopted procedure does not conflict with operating guidelines and scientific literature on the matter. Problematic cases include the management of trials with a predominant active metabolite, the absence of a reliable analytical bioassay, the availability of various strengths of the same drug on the market, a wide acceptability titre range, the management of studies on topical drugs that are devoid of systemic activity, the management of drugs that cannot be given for ethical reasons to healthy subjects or that may cause adverse events, especially when a steady state design is required. The parallel group study design appears to be more appropriate than the cross-over or the individual bioequivalence design in assessing drugs with a long half-life. Some pharmacokinetic and statistical analysis-related issues are also discussed such as the sequence/period interaction sometimes encountered in these trials, which, in the absence of the carry-over effect, does not bias the bioequivalence results and the need to process data with non-compartmental pharmacokinetic analysis.