. Author manuscript; available in PMC: 2021 Nov 1.

Published in final edited form as: Clin Pharmacol Ther. 2020 May 31;108(5):1010–1017. doi: 10.1002/cpt.1885

Table 2.

Prespecified time-varying covariates included in conditional Poisson regression models

Category	Subcategory	Component	Identification method
Drugs that can increase the risk of bleeding	Antiplatelet agents^a	abciximab, aspirin, cangrelor, cilostazol, clopidogrel, dipyridamole, eptifibatide, prasugrel, ticagrelor, ticlopidine, tirofiban, vorapaxar	NDC, dispensing date, days supplied
	NSAIDs^a	celecoxib, diclofenac, diflunisal, etodolac, fenoprofen, flurbiprofen, ibuprofen, indomethacin, ketoprofen, ketorolac, meclofenamate, meloxicam, nabumetone, naproxen, oxaprozin, piroxicam, salsalate, sulindac, tolmetin	NDC, dispensing date, days supplied
	SNRIs^a	desvenlafaxine, duloxetine, levomilnacipran, milnacipran, venlafaxine	NDC, dispensing date, days supplied
	SSRIs^a	citalopram, escitalopram, fluoxetine, fluvoxamine, milnacipran, paroxetine, sertraline	NDC, dispensing date, days supplied
Drugs that can increase INR	CYP1A2 inhibitors	enoxacin^b, gatifloxacin^b, propranolol^a	NDC, dispensing date, days supplied
	CYP2C9 inhibitors	amiodarone^a, amoxicillin^b, co-trimoxazole^b, etravirine^a, fluconazole^b, fluvoxamine^a, metronidazole^b, miconazole^b, oxandrolone^a, voriconazole^b	NDC, dispensing date, days supplied
	CYP3A4 inhibitors	atorvastatin^a, azithromycin^b, erythromycin^b, gemfibrozil^a, prednisone^a, propafenone^a, rosuvastatin^a, simvastatin^a	NDC, dispensing date, days supplied
	Drugs increasing vitamin K catabolism^a	thyroid hormones (levothyroxine, liothyronine, liotrix)	NDC, dispensing date, days supplied
	Drugs that can cause protein displacement^a	phenytoin, sulfinpyrazone	NDC, dispensing date, days supplied
	Drugs with unknown mechanism	acetaminophen^a, cefamandole^b, cefazolin^b, quinidine^a	NDC, dispensing date, days supplied
Drugs that can reduce INR	Inducers of drug metabolism	amobarbital^a, carbamazepine^a, cholestyramine^a, griseofulvin^b, phenobarbital^a, propylthiouracil^a, rifampin^b, secobarbital^a	NDC, dispensing date, days supplied
Major non-chronic condition that may affect bleeding risk	Acute infection^b	Acute infection identified at any position of discharge diagnosis on inpatient or outpatient claims	ICD-9-CM diagnosis codes, admission or service date
Warfarin monitoring^*	Therapeutic drug monitoring for warfarin^c	INR testing/monitoring, prothrombin time testing/monitoring, identified at any-position of any claim-type procedure codes	CPT, HCPCS^d
Average daily dose of object drug^*	Average daily dose of warfarin^e	Defined by [(quantity × strength) / (days supplied)]	NDC, dispensing date, days supplied, quantity, strength

NDC: National Drug Code. NSAID: nonsteroidal anti-inflammatory drug. SNRI: serotonin and norepinephrine reuptake inhibitor. SSRI: selective serotonin reuptake inhibitor. INR: international normalized ratio. CYP: cytochrome P450 enzyme. ICD-9-CM: International Classification of Diseases 9th Revision Clinical Modification. CPT: Current Procedural Terminology. HCPCS: Healthcare Common Procedure Coding System.

Measured as a day-level binary variable indicating being dispensed on the current day (refers to each day during the observation time as current) or any time during the 31 days prior to the current day.

Measured as a day-level binary variable indicating being diagnosed on the current day or any time during the 15 days prior to the current day.

Measured as a day-level binary variable indicating warfarin monitoring conducted on the current day or any time during the 7 days prior to the current day.

CPT codes 99363, 99364, 3555F, 85610, 85611 and HCPCS codes G0249, G0250.

Measured as a day-level continuous variable on the current day, based on the prescription active on the current day. In the analysis controlling for warfarin average daily dose, while Medicare claims from Ohio were included, Medicaid claims from Ohio were excluded due to lack of information on days supplied.

Covariates additionally adjusted in the sensitivity analyses.