ABSTRACT
BACKGROUND: The fixed-dose combination of aspirin (acetylsalicylic acid) 25 mg plus extended-release dipyridamole 200 mg (ASA+ER-DP) is used for long-term secondary stroke prevention in patients who have experienced non-cardioembolic stroke or transient ischemic attack. Although the theoretical risk is low that the antiplatelet activity of ASA+ER-DP will be affected by concomitant use of a proton pump inhibitor (PPI), no formal drug-drug interaction studies have been conducted. OBJECTIVE: This study aimed to determine whether the PPI omeprazole influences the pharmacokinetic (PK) and pharmacodynamic (PD) behavior of ASA+ER-DP. STUDY DESIGN AND SETTING: This was a randomized, open-label, multiple-dose, crossover, drug-drug interaction study carried out in a clinical trial unit. PARTICIPANTS: Sixty healthy male and female volunteers aged 18-50 years were included in the study. INTERVENTION: Participants were randomized to one of two treatment sequences (ABCD or CDAB), each comprising four 7-day treatments with a washout of ≥14 days between the second and third treatments. Treatment A=ASA+ER-DP 25 mg/200 mg (Aggrenox®) twice daily (BID) alone; B=ASA+ER-DP 25 mg/200 mg BID+omeprazole (Prilosec®) 80 mg once daily (QD) following ASA+ER-DP alone for 7 days; C=omeprazole 80 mg QD alone; D=omeprazole 80 mg QD+ASA+ER-DP 25 mg/200 mg BID following omeprazole alone for 7 days. MAIN OUTCOME MEASURES: The main outcome measures were systemic PK exposure to ER-DP and ASA inhibition of arachidonic acid-induced platelet aggregation. RESULTS: Systemic exposure to ER-DP was similar with and without omeprazole, based on steady-state area under the concentration-time curve (AUC) from 0 to 12 h (AUC0-12,ss, ng·h/mL) and maximum plasma concentration (Cmax,ss, ng/mL). For the treatment comparison D versus A, the percent mean ratios were 96.38 (90% confidence interval [CI] 90.96-102.13) for AUC0-12,ss and 92.03 (86.95-97.40) for Cmax,ss. The ER-DP concentration versus time profiles were nearly superimposable. There was no effect on the PDs of the ASA component: the extent of ASA inhibition of arachidonic acid-induced platelet aggregation was almost identical with and without omeprazole, with a percent mean ratio for treatment D versus A = 99.02 (90 % CI 98.32-99.72) at 4 h after last dose. All treatments were well tolerated. CONCLUSION: The PK and PD behavior of ASA + ER-DP was not altered by concurrent administration of omeprazole.
Subject(s)
Aspirin/pharmacokinetics , Dipyridamole/pharmacokinetics , Omeprazole/pharmacokinetics , Platelet Aggregation Inhibitors/pharmacokinetics , Platelet Aggregation/drug effects , Proton Pump Inhibitors/pharmacokinetics , Adolescent , Adult , Aspirin/administration & dosage , Aspirin/adverse effects , Aspirin, Dipyridamole Drug Combination , Cross-Over Studies , Dipyridamole/administration & dosage , Dipyridamole/adverse effects , Drug Combinations , Drug Interactions , Drug Therapy, Combination , Female , Humans , Male , Middle Aged , Omeprazole/administration & dosage , Omeprazole/adverse effects , Platelet Aggregation Inhibitors/administration & dosage , Platelet Aggregation Inhibitors/adverse effects , Proton Pump Inhibitors/administration & dosage , Proton Pump Inhibitors/adverse effects , Young AdultABSTRACT
Dipyridamole (DP) is an antiplatelet agent that shows decreased oral bioavailability with increased gastric pH that occurs with commonly prescribed antacids. An extended-release (ER) formulation of DP that employs tartaric acid to improve bioavailability of DP in the presence of elevated gastric pH was developed as a combination antiplatelet product with immediate-release aspirin. This crossover-designed study examined the relative bioavailability of DP from the composite product compared to conventional DP tablets during reduced gastric acidity. Gastric pH was increased (pH > 4.0) in 20 healthy subjects with lansoprazole (30 mg/d for 5 days). Dipyridamole systemic exposure over 12 hours was compared after oral administration of a single composite ER capsule (200 mg DP + 25 mg aspirin) versus two 100-mg conventional DP tablets given 6 hours apart combined with 81 mg aspirin. DP relative bioavailability was reduced 53% with conventional tablets compared to the composite buffered ER capsule in reduced gastric acid conditions. Peak DP plasma concentrations were 57% lower with immediate-release tablets compared to the composite formulation with high stomach pH. Substituting generic DP plus low-dose aspirin may be less effective than the buffered DP composite product in patients with concomitant antacid therapies.
Subject(s)
Achlorhydria/metabolism , Dipyridamole/pharmacokinetics , Platelet Aggregation Inhibitors/pharmacokinetics , Adult , Aspirin/administration & dosage , Biological Availability , Cross-Over Studies , Dipyridamole/administration & dosage , Dipyridamole/blood , Drug Combinations , Female , Humans , Male , Middle Aged , Platelet Aggregation Inhibitors/administration & dosage , Platelet Aggregation Inhibitors/blood , Tablets, Enteric-CoatedABSTRACT
A new 5-HT(1A) silent antagonist 14 (5-HT(1A) IC(50)=2.2 nM) antagonizes the effects of agonists on reciprocal forepaw treading behavior, on neuronal firing in the rat dorsal raphé, and on 5-HT(1A) release in the raphé and hippocampus. While 14 alone was inactive in the social interaction paradigm, it completely reversed the social interaction activity of the serotonergic compounds (buspirone, 1, and 2).
