Anticoagulation: a 5 mg loading dose was more successful than 10 mg

Clinical bottom line (level 1b)

Patients starting anticoagulation who received a loading dose of 5 mg compared with 10 mg were more likely to have their INR 2.0-3.0 for 2 consecutive days and never above 3.0 (NNT = 2 at 5 days) .
There was no clear effect on the number of patients who have a supratherapeutic INR.

Crowther et al: Archives of Internal Medicine 1999; 159: 46-48

Expires October 2003

The study

Unblinded ?concealed randomised trial without intention-to-treat
Setting: thromboembolism unit, university hospital, Canada

53 patients (aged mean 66, 53% female) starting anticoagulation with warfarin

Excluded if

contraindication to warfarin

geographically inaccessible

Control Group: (n = 21, 21 analysed): loading dose of 10 mg warfarin
Experimental Group: (n = 32, 31 analysed): loading dose of 5 mg warfarin

98% followed for 5 days Warfarin was subsequently given using a dosing protocol based on daily INR measurements.

The evidence

Outcome	Time to outcome	CER	EER	RRR (95% CI)	ARR (95% CI)	NNT (95% CI)
INR 2.0 to 3.0 on 2 consecutive days, and never > 3.0	5 days	5 (23.8%)	21 (65.63%)	55% (23% to 74%)	43.82% (17.27% to 66.36%)	2 (2 to 6)
INR > 3.0	5 days	5 (23.8%)	2 (6.25%)	74% (-23% to 94%)	17.56% (-2.50% to 37.61%)	6 (NNT = 3 to infinity; NNH = 40 to infinity)

Comments

The study is too small to show any difference between the 2 regimens for over anticoagulation.

Citation

Crowther MA, Ginsberg JB, Kearon C, et al: A randomized trial comparing 5-mg and 10-mg warfarin loading doses. Archives of Internal Medicine 1999; 159: 46-48

Search Terms: ?
Contributor: Chris Ball and Musab Hayatli, October 1999
Reviewer:

_{Clinical Question.}

_Patient	_{starting anticoagulation}
_{Intervention or Exposure}	_{warfarin 5 mg loading dose}
_Comparison	_{warfarin 10 mg loading dose}
_Outcome	_{successful anticoagulation}