A piroxicam-warfarin interaction is presented with a discussion of the possible mechanism of action. A 60-year-old white male on warfarin therapy for recurrent pulmonary embolism and deep venous thrombophlebitis showed a decrease in his previously therapeutic and stable prothrombin time when piroxicam was discontinued from his drug regimen. On two rechallenges over a ten-month period, his prothrombin times showed consistent and clinically significant fluctuations as piroxicam was added and deleted from his drug regimen.
WisemanEHHobbsDC. Review of pharmacokinetic studies with piroxicam. Am J Med1982; 73 (Feb 16):9–17.
2.
HarveySC. Hypnotics and sedatives. In: GilmanAGGoodmanLSGilmanA., eds. The pharmacological basis of therapeutics. New York: Macmillan, 1980: 339–75.
3.
CohenMR. Focus on the newest nonsteroidal antiinflammatory agents. Hasp Pharm1982; 17: 628–30.
4.
HobbsDCTwomeyTM. Piroxicam pharmacokinetics in man; aspirin and antacid interaction studies. J Clin Pharmacol1979; 19: 270–81.
5.
DahlSLWardJR. Pharmacology, clinical efficacy, and adverse effects of piroxicam, a new nonsteroidal antiinflammatory agent. Pharmacotherapy1982; 2: 80–9.
6.
JacototB. Piroxicam a new non-steroidal anti-inflammatory agent. In: Proceedings of the 19th European Congress of Rheumatology. Wiesbaden, Germany, September 4, 1979: 46–7.
7.
NikiG. Non-steroidal analgesic and anti-inflammatory agents. Br Med J1983; 287: 39–43.
8.
BrogdenRNHeelRCSpeightTMAveryGS. Piroxicam: A review of its pharmacological properties and therapeutic efficacy. Drugs1981; 22: 165–87.
WagnerJG. Pharmacokinetic data: Pharmacokinetic parameters estimated from intravenous data by uniform methods and some of their uses. J Pharmacokinet Biopharm1977; 5: 161–82.
15.
O'reillyRALevyG. Pharmacokinetic analysis of potentiating effect of phenylbutazone on anticoagulant action of warfarin in man. J Pharm Sci1970; 59: 1258–61.
LevyGYacobiA. Effect of plasma protein binding on elimination of warfarin (letter). J Pharm Sci1974; 63: 805.
18.
GibaldiMMcNamaraPJ. Apparent volumes of distribution and drug binding to plasma proteins and tissues. Eur J Clin Pharmacol1978; 13: 373.
19.
GreenblattDJ. Reduced serum albumin concentrations in the elderly: A report from the Boston Collaborative Drug Surveillance Program. J Am Geriatr Soc1979; 27: 20.
20.
BresslerR. Understanding adverse drugs reactions in the elderly. Drug Therapy1981; 11 (2):71–80.
21.
WoolfADRogersHJBradbrookIDCorlesD. Does age alter piroxicam plasma concentrations?In-house report, Pfizer, Inc., New York, NY, January 11, 1983.
22.
WoolfADRogersHJBradbrookIDCorlesD. Pharmacokinetic observations on piroxicam in young adults, middle-aged and elderly patients. Br J Clin Pharmacol1983; 16: 433–7.
23.
RickeyDTBenderAD. Pharmacokinetic consequences of aging. Annu Rev Pharmacol Toxicol1977; 17: 49–65.
24.
RoweJWAndrewRTobinJDNorrisAHShockNW. The effect of age on creatinine clearance in man; a cross sectional and longitudinal study. J Gerontol1976; 31: 155–63.
25.
LewisRJTragerWFChanKK. Warfarin; stereochemical aspects of its metabolism and the interaction with phenylbutazone. J Clin Invest1974; 53: 1607–17.
26.
CrookJO'malleyKStevensonIH. Pharmacokinetics in the elderly. Clin Pharmacokinet1976; 1: 280–96.
27.
O'reillyRA. Anticoagulant, antithrombotic, and thrombolytic drugs. In: GilmanAGGoodmanLSGilmanA., eds. The pharmacological basis of therapeutics. New York: Macmillan, 1980: 1347–69.
28.
GodbillonJRichardJGerardinAMeinertzTKasperWJahnchenE. Pharmacokinetics of the enantiomers of acenocoumarol in man. Br J Clin Pharmacol1981; 12: 621–9.
