Table 2.
Prevalence of interactions
| Group (number of veterans dispensed medicine during follow-up) | Interacting drug(s): | Patients dispensed interacting drug pair (%) |
|---|---|---|
| Warfarin (n = 19 049) | NSAIDs | 1373 (7.2%) |
| Anti-platelet medicines | 1124 (5.9%) | |
| Miconazole (or other imidazoles) | 0 | |
| Allopurinol (n = 11 981) | Mercaptopurine | 0 |
| Azathioprine | 3 (0.0%) | |
| Amiloride (n = 360) | Potassium salts | 10 (2.8%) |
| ACE inhibitors | 3 (0.8%) | |
| Tacrolimus | 0 | |
| Amiodarone (n = 4875) | Thioridazine | 0 |
| Quinidine | 0 | |
| Chlorpromazine | 2 (0.0%) | |
| Disopyramide | 0 | |
| Haloperidol | 17 (0.3%) | |
| Phenothiazines | 113 (2.3%) | |
| Sotalol | 11 (0.2%) | |
| Digoxin | 300 (6.2%) | |
| Verapamil (n = 7705) | β-adrenoceptor blockers | 412 (5.3%) |
| Cyclosporin (n = 32) | Orlistat | 0 |
| Statins | 15 (46.9%) | |
| Spironolactone (n = 3308) | Amiloride | 2 (0.1%) |
| Potassium salts | 135 (4.1%) | |
| ACE inhibitors | 61 (1.8%) | |
| Lithium | 4 (0.1%) | |
| Tacrolimus/sirolimus | 0 | |
| Methotrexate (n = 783) | Aspirin | 88 (11.2%) |
| NSAIDs | 188 (24.0%) | |
| Sildenafil, tadalafil, vardenafil (n = 2563) | Nitrates | 22 (0.9%) |
| Atenolol (n = 22 956) | Clonidine | 30 (0.1%) |
| Carbamazepine (n = 1128) | Dextropropoxyphene | 8 (0.7%) |
| Imipramine (n = 1086) | Clonidine | 0 |
| Entacapone | 0 | |
| Moclobemide | 3 (0.3%) | |
| Itraconazole (n = 16) | Pimozide | 0 |
| Simvastatin/atorvastatin | 5 (31.3%) | |
| Tacrolimus/sirolimus | 0 | |
| Quinidine | 0 | |
| Lithium (n = 278) | Haloperidol | 2 (0.7%) |
| ACE inhibitor or AIIRB | 49 (17.6%) | |
| Furosemide | 12 (4.3%) | |
| Hydrochlorothiazide | 0 | |
| Phenothiazines | 9 (3.2%) | |
| Tramadol (n = 6433) | Monoamine oxidase inhibitors | 0 |
| Pravastatin (n = 12 827) | Gemfibrozil | 52 (0.4%) |
| Triptans (n = 175) | Ergot alkaloids | 3 (1.7%) |
| Monoamine oxidase inhibitors | 2 (1.1%) | |
| Methysergide | 5 (2.9%) | |
| SSRIs | 22 (12.6%) | |
| Captopril (n = 22 956) | Potassium salts | 413 (1.8%) |
| Diclofenac (n = 4881) | Heparin | 8 (0.2%) |
| Digoxin (n = 8992) | Quinidine | 14 (0.2%) |
| Fluoxetine (n = 2368) | Moclobemide | 0 |
| Selegiline | 0 |