Antithrombotic Therapy for Stroke Patients with Cardiovascular Disease

Prevention of ischemic stroke relies on the use of antithrombotic medications comprising antiplatelet agents and anticoagulation. Stroke risk is particularly high in patients with cardiovascular disease. This review will focus on the role of antithrombotic therapies in the context of different types of cardiovascular disease. We will discuss oral antiplatelet medications and both IV and parental anticoagulants. Different kinds of cardiovascular disease contribute to stroke via distinct pathophysiological mechanisms, and the optimal treatment for each varies accordingly. We will explore the mechanism of stroke and evidence for antithrombotic therapy in the following conditions: atrial fibrillation, prosthetic heart values (mechanical and bioprosthetic), aortic arch atherosclerosis, congestive heart failure (CHF), endocarditis (infective and nonbacterial thrombotic endocarditis), patent foramen ovale (PFO), left ventricular assist devices (LVAD), and extracorporeal membrane oxygenation (ECMO). While robust data exist for antithrombotic use in conditions such as atrial fibrillation, optimal treatment in many situations remains under active investigation.

Relative Bioavailability of Methylphenidate Extended-release Chewable Tablets Chewed Versus Swallowed Whole

PURPOSE

Methylphenidate hydrochloride extended-release chewable tablet (MPH ERCT) is approved for treatment of attention deficit hyperactivity disorder in patients aged 6 years and older. This article evaluates the pharmacokinetic parameters and relative bioavailability of MPH ERCT when chewed versus swallowed whole.

METHODS

In this open-label, single-dose, 3-period, 3-treatment crossover study, 12 healthy adult volunteers were randomly assigned to treatment sequence. In each period, subjects received a single 40-mg dose of the assigned treatment (MPH ERCT chewed, MPH ERCT swallowed whole, or methylphenidate extended-release oral suspension [MEROS]). Blood samples for pharmacokinetic analysis were collected for 24 hours postdose. Key pharmacokinetic parameters included C_max, AUC_0-t, and AUC_0-∞.

FINDINGS

The geometric mean values for AUC_0-t, AUC_0-∞, and C_max were similar for MPH ERCT chewed, MPH ERCT swallowed whole, and MEROS. In all pairwise between-treatment comparisons, the 90% CIs of the geometric mean ratios for AUC_0-t, AUC_0-∞, and C_max were fully contained within the bioequivalence range of 80% to 125%. Early exposure over the first 4 hours after dosing (AUC_0-4) was similar for MPH ERCT chewed versus swallowed whole; AUC_0-4 was approximately 15% lower for MPH ERCT, either chewed or swallowed, compared with MEROS. Each treatment was generally well tolerated.

IMPLICATIONS

There was no difference in overall rate or extent of exposure of methylphenidate when MPH ERCT was chewed versus swallowed whole by healthy volunteers.

Acetylsalicylic acid in critically ill patients: a cross-sectional and a randomized trial

BACKGROUND

Despite decades of clinical use, the pharmacokinetics and the effects of acetylsalicylic acid (ASA) in critically ill patients remain ill-defined. We aimed to investigate the pharmacokinetics and the effects of different ASA formulations during critical illness.

DESIGN

A cross-sectional study and a randomized, parallel-group trial were performed. Critically ill patients under chronic oral ASA treatment (100 mg enteric-coated) were screened for high 'on-treatment' platelet reactivity (HTPR) according to arachidonic acid-induced whole-blood aggregometry. Thirty patients with HTPR were randomized to receive 100 mg ASA intravenously, 100 mg enteric-coated ASA bid (bis in die) or 81 mg chewable ASA (n = 10 per group). Serum thromboxane B2 (TXB2) levels, ASA and salicylic acid levels were quantified.

RESULTS

Of 66 patients, 85% (95% confidence intervals 74-93%) had HTPR. Compared to baseline infusion of 100 mg, ASA significantly reduced platelet aggregation after 24 h to median 80% (Quartiles: 66-84%). Intake of 81 mg chewable ASA significantly reduced platelet aggregation to 75% (54-86%) after four hours, but increased it to 117% after 24 h (81-163%). Treatment with 100 mg enteric-coated ASA bid decreased platelet aggregation after 24 h to median 56% (52-113%). Baseline TXB2 levels were median 0·35 ng/mL (0·07-0·94). Infusion of ASA or intake of 100 mg ASA bid reduced TXB2 levels to 0·07-0·18 ng/mL after 24 h, respectively. Chewable ASA reduced TXB2 levels only transiently. Pharmacokinetic analysis revealed highly variable absorption patterns of oral ASA formulations.

CONCLUSION

There is a very high prevalence of HTPR in critically ill patients on peroral ASA therapy, caused by an incomplete suppression of TXB2 and/or by impaired absorption of ASA.

Transfer of Low Dose Aspirin Into Human Milk

BACKGROUND

Aspirin has antipyretic and anti-inflammatory properties and is frequently used by pregnant and lactating women. However, its transfer in human milk when administered at low dose has not been reported. Research aim: This study aimed to evaluate the transfer of acetylsalicylic acid and its metabolite, salicylic acid, into human milk following the use of low dose aspirin.

METHODS

In this study, milk samples were collected at 0, 1, 2, 4, 8, 12, and 24 hours from seven breastfeeding women after a steady-state daily dose of 81 mg of aspirin. Milk levels of acetylsalicylic acid and salicylic acid were determined by liquid chromatography-tandem mass spectrometry.

RESULTS

Acetylsalicylic acid levels were below the limit of quantification (0.61 ng/ml) in all the milk samples, whereas salicylic acid was detected at very low concentrations. The average concentration of salicylic acid observed was 24 ng/ml and the estimated relative infant dose was 0.4%.

CONCLUSION

Acetylsalicylic acid transfer into milk is so low that it is undetectable even by highly sophisticated methodology. Salicylic acid does appear in the human milk in comparatively low amounts, which are probably subclinical in infants. Thus, the daily use of an 81-mg dose of aspirin should be considered safe during lactation.

Prospective, randomised trial of the time dependent antiplatelet effects of 500 mg and 250 mg acetylsalicylic acid i. v. and 300 mg p. o. in ACS (ACUTE)

Little is known about the onset of action after intravenous or oral administration of acetylsalicylic acid (ASA) in patients with acute coronary syndromes (ACS). The aim of the study was to compare intravenous 250 or 500 mg acetylsalicylic acid (ASA) with oral 300 mg in ASA naïve patients with ACS concerning the onset of antiplatelet effects measured by time dependent thromboxane inhibition. A total of 270 patients with ACS < 24 hours were randomised into one of three treatment arms comprising administration of a single dose of ASA as soon as possible after admission. The primary endpoint was platelet inhibition assessed by measurement of arachidonic acid (AA)-induced platelet thromboxane release (TXB₂) 5 minutes (min) after study drug administration. Both 250 mg and 500 mg ASA i. v. inhibited TXB₂ formation nearly completely (geometric means: from 581.7 and 573.9 ng/ml at baseline to 3.9 and 3.1 ng/ml at 5 min, respectively) compared to 300 mg oral ASA (geometric means: from 652.0 to 223.7 ng/ml) (p-value, ANCOVA: < 0.0001). Similar results were obtained for inhibition of AA-induced platelet aggregation (Multiplate ASPItest; from means 86.41 and 85.72 U to 23.04 and 20.57 U at 5 min, respectively) compared to 300 mg oral ASA from mean 87.18 to 75.56 U (p-value, ANCOVA: <0.0001). The rate of bleedings was low and comparable between the groups. In summary, the administration of a single dose of 250 or 500 mg ASA IV compared to 300 mg orally is associated with a faster and more complete inhibition of thromboxane generation and platelet aggregation. Bleeding complications were comparable between the groups.

Towards evidence-based emergency medicine: best BETs from the Manchester Royal Infirmary. BET 1: Which form of aspirin is the fastest to inhibit platelet aggregation in emergency department patients with non-ST segment elevation myocardial infarction?

A short cut review was carried out to establish whether, in patients with suspected acute coronary syndromes presenting to the emergency department, what form of aspirin has the most rapid onset of action. Papers comparing the speed of onset of chewable aspirin, or soluble aspirin or solid aspirin were included. This summarises all three parts of a combined best evidence topic report (BET). The clinical bottom line is that chewable aspirin may be faster than soluble aspirin at decreasing the amount of time to achieve platelet inhibition in a patient. Soluble aspirin is faster than whole solid aspirin, which is faster than enteric-coated aspirin.

Therapeutic concerns when oral medications are administered nasogastrically

WHAT IS KNOWN AND OBJECTIVE

Administering oral medications to patients with nasogastric tube (NGT) is a challenging patient-care issue. Inappropriate prescribing behaviour and incorrect procedure for extemporaneous preparation of oral suspensions given via NGT may result in significant harm to patients. There are many drugs which have not been tested regarding oral absorption profile and bioavailability derived from NGT dosing. Although several studies and case-reports have been reported, there is no up-to-date review of drug administration via NGT. The aim of this review is to increase awareness of rational drug administration via NGT and to encourage relevant research in this area.

METHODS

Full prescribing information from each currently available oral medication was reviewed for any data indicating that the medication could not be crushed or opened. Literature was identified by searching PubMed (1988 to Aug 2012).

RESULTS AND DISCUSSION

There is evidence to show that NGT dosing of some medications may bring both benefits (e.g. cost saving) and disadvantages (e.g. decrease in efficacy and/or safety). For medications with package inserts that warn that they should not be crushed or opened, alternatives are usually recommended. However, in some cases, there is evidence to support NGT dosing. Sometimes special procedures are required to avoid problems such as instability, interaction with enteral nutrition, adsorption, tube obstruction and low recovery when preparing extemporaneous oral suspensions.

WHAT IS NEW AND CONCLUSION

Physicians, pharmacists and nurses should know the procedures for drug administration by NGT, as well as the latest evidence on such administrations. There may not be bioequivalence between oral and nasogastric administrations. Care must be taken to avoid compromising the physicochemical, biopharmaceutical and pharmacological properties of drugs given by NGT to ensure their safety and efficacy.