Table 2 Drug-Drug Interactions: This table is not completely inclusive, but rather meant to highlight drug-drug interactions between antimalarial drugs, travelers’ diarrhea antibiotics, altitude illness prevention medications and other common drugs prescribed in the elderly
From: Guidelines for the prevention of travel-associated illness in older adults
DRUG | DRUGS INTERACTING | RECOMMENDATION | ADVERSE EFFECTS |
|---|---|---|---|
ANTIMALARIALS | |||
 Mefloquine | Carbamazepine, Phenytoin, Phenobarbitol, Valproic acid | Consider therapy modification | Diminished effect of antiepileptic. Mefloquine contraindicated for malaria prophylaxis in patients with history of seizure disorder. |
Citalopram, Fluoxetine | Consider therapy modification | QTc prolongation | |
Azithromycin | Monitor therapy | QTc prolongation | |
Diltiazem, Verapamil, Carvedilol | Monitor therapy | Increased serum concentrations of mefloquine | |
Compazine | Monitor therapy | Increased serum concentrations of Compazine | |
Warfarin | Monitor therapy | May increase anticoagulant effect | |
 Chloroquine | Amiodarone, Fluoxetine, Sotalol | Avoid combination | High risk QTc prolongation |
Cyclosporine | Consider therapy modification | May increase serum concentrations of cyclosporine | |
Paroxetine, Ritonavir, Lopinavir, Ketaconazole, Fluconazole | Consider therapy modification | May increase serum concentration of chloroquine | |
Ciprofloxacin, Levofloxacin, Azithromycin | Consider therapy modification | QTc prolongation | |
Carvedilol, Propranolol, Metoprolol | Monitor therapy | May increase serum concentrations of beta-blocker | |
Digoxin | Monitor therapy | May increase serum concentrations of digoxin | |
Tacrolimus | Monitor therapy | QTc prolongation | |
 Atovaquone-Proguanil | Ritonavir, Rifampin, Riabutin, Rifapentine | Avoid combination | May decrease the serum concentration of Atovaquone |
Efavirenz, Metoclopramide | Consider therapy modification | May decrease the serum concentration of Atovaquone | |
Compazine | Monitor therapy | May increase serum concentration of Compazine | |
Warfarin | Monitor therapy | May increase anticoagulant effect | |
 Doxycycline | Calcium salts, Carbamazepine, Phenytoin | Consider therapy Modification | May decrease serum concentrations of doxycycline |
Methotrexate | Monitor therapy | May increase serum concentrations of methotrexate | |
Warfarin | Monitor therapy | May increase anticoagulation effect | |
TRAVELERS’ DIARRHEA ANTIBIOTICS | |||
 Azithromycin Fluoro-quinolones | Citalopram, Fluoxetine, Escitalopram, Amiodarone, Dronedarone | Avoid combination | High risk QTc prolongation |
Atorvastatin, simvastatin | Monitor therapy | May enhance myopathic (rhabdomyolysis) effect | |
Warfarin | Monitor therapy | May increase anticoagulant effect | |
Multivitamins/Minerals (ADEK, folate, iron), Calcium salts | Consider therapy modificationa | May decrease serum concentrations of quinolone | |
ALTITUDE SICKNESS PREVENTION | |||
 Acetazolamide | Brinzolamide, dorzolamide | Avoid combination | Increased risk for metabolic acidosis and nephrolithiasis |
Topirimate, zonisamide | Avoid combination | Increased risk for metabolic acidosis and nephrolithiasis | |
Aspirin (>81Â mg/day), bismuth subsalicylate | Consider therapy Modification | Metabolic acidosis | |
Tramadol, oxycodone, hydromorphone, codeine | Monitor therapy | Risk of orthostatic hypotension | |
Dextroamphetamine/amphetamine | Monitor therapy | Decreased excretion of amphetamines | |
Lithium | Monitor therapy | Increased lithium excretion | |
Metformin | Monitor therapy | Increased risk of lactic acidosis | |
Quinidine | Monitor therapy | Decreased excretion of quinidine | |