LETTER TO THE EDITOR

Rivaroxaban use following bariatric surgery

Zachariah Thomas • Yaron Bareket •

Wendy Bennett

� Springer Science+Business Media New York 2014

The recent case report by Dr. Mahlmann et al. [1]

describing the pharmacokinetics of rivaroxaban in a bari-

atric surgery patient is a welcome addition to the literature.

However, we feel it necessary to clarify the statement made

regarding the ‘‘high bioavailability’’ of rivaroxaban and

express caution regarding the use of this agent in postop-

erative bariatric surgery patients.

The bioavailability of rivaroxaban depends on the dose

and also the presence of food. Studies have shown that

rivaroxaban doses up to 10 mg have high bioavailability.

However, higher doses, which are employed for the pre-

vention of stroke in atrial fibrillation and the treatment of

venous thromboembolism (VTE), have poor bioavailability

(*66 % for a 20 mg dose) [2, 3]. In pharmacokinetic

studies, the bioavailability of higher doses is markedly

improved (C80 %) when taken with food [2]. For this

reason, the rivaroxaban prescribing information states that

it should be taken ‘‘with food’’ for the atrial fibrillation and

VTE treatment indications [4]. ‘‘With food’’ is a rather

vague description with interpretations ranging from ‘‘take

with a small snack’’ to ‘‘take with a full meal.’’ In the

ROCKET–AF trial, patients were instructed to take their

dose with their evening meal, but no specific calorie or size

requirements were specified [5]. In the VTE treatment

studies, patients were instructed to take their doses with

meals with no further specifications [6, 7].

In the previously mentioned pharmacokinetic studies,

‘‘with food’’ was specifically a large meal of approximately

1,000 kcal [2]. While it is doubtful that subjects receiving

rivaroxaban in clinical trials took their doses with such a

large caloric intake, it seems reasonable to presume their

doses were taken with standard meals and that their caloric

intake was essentially normal (*1,800–2,500 kcal per day

in the USA) [8].

Venous thromboembolism is a cause of morbidity and

mortality after gastric bypass surgery and obesity increases

the risk of atrial fibrillation [9, 10]. The relative ease of

rivaroxaban compared to traditional agents may make it an

attractive option for patients experiencing these events

after bariatric surgery. To our knowledge, there are no

clinical trial data to support the use of rivaroxaban for these

indications specifically in bariatric surgery patients.

Although the report by Mahlmann et al. [1] and a previous

study that suggests that rivaroxaban is not influenced by

extremes of weight [11] offers some reassurance, other

factors must be considered before rivaroxaban is used in

these patients. Specifically, we believe that patients who

are in the early postoperative period after bariatric surgery

should not receive rivaroxaban for either the atrial fibril-

lation or VTE treatment indications due to the low caloric

intake (*500 calories per day) that is characteristic of the

diets that these patients are placed on postoperatively [12].

In Dr. Mahlmann’s report [1], rivaroxaban was started

several months after bariatric surgery and thus this

patient’s caloric intake would likely have been much closer

to normal relative to the postoperative period. Since the

minimum amount of food required ensuring adequate

absorption of rivaroxaban has not been determined, it is

quite plausible that the low calorie consumption of the

postoperative gastric bypass patient is insufficient to sup-

port adequate rivaroxaban absorption. Furthermore,

Z. Thomas (&) � Y. Bareket � W. Bennett

Hackensack University Medical Center, 30 Prospect Avenue,

Hackensack, NJ 07601, USA

e-mail: zthomas@rci.rutgers.edu

Z. Thomas

Ernest Mario School of Pharmacy, Rutgers, The State University

of New Jersey, Piscataway, NJ, USA

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J Thromb Thrombolysis

DOI 10.1007/s11239-014-1057-6

decreased absorption would likely lead to reduced intensity

anticoagulation. Subtherapeutic anticoagulation has been

linked to poor outcomes in patients experiencing VTE and

atrial fibrillation [13–15]. Given the unavailability of rou-

tine monitoring techniques for rivaroxaban and the absence

of a well defined therapeutic range, until more data are

available, we would advise against the use of rivaroxaban

in these patients, particularly in the early postoperative

period when caloric intake is minimal. We encourage the

manufacturer to conduct and sponsor studies of rivarox-

aban in special populations such as this.

Conflict of interest Drs. Bareket and Thomas report receiving

consulting fees from Janssen Pharmaceuticals, the manufacturer of

rivaroxaban.

References

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Z. Thomas et al.

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