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1334 D-Dimer Digoxin, Serum Level

Reference Interval • Coadministration of azole antifungals, Pearls
Canine range: peak (1.5-2 hours postdose) amphotericin B, azithromycin, acetazol- • Metabolites may be active, so monitor
VetBooks.ir next 12-hour dose): 400-600 ng/mL (immuno- corticosteroids, and metronidazole increase levels of parent compound to reduce risk
amide, cisapride, ciprofloxacin/enrofloxacin,
response to therapy in addition to blood
800-1400 ng/mL; trough (immediately before
of toxicosis.
suppression), 100-300 ng/mL (perianal fistula),
blood cyclosporine levels.
250 ng/mL (inflammatory bowel disease)
Specimen Collection and Handling • High Performance Liquid Chromatography
(HPLC) was previously considered the gold
Causes of Abnormally High Levels EDTA whole blood (lavender top tube). Ship standard assay for cyclosporine determination
Overdosage, hepatic dysfunction, interaction overnight on ice. Check within 3-5 days of but has largely been replaced by Fluorescence
with drugs (see below) initiating therapy, then at 2- to 4-week intervals Polarization Immunoassay (FPIA).
until steady therapeutic response. Though peak • Pharmacodynamic monitoring may be used as
Causes of Abnormally Low Levels and trough levels are ideal initially, single 2-hour an alternative: http://www.cvm.msstate.edu/
Interaction with drugs (see below), insufficient peak sample may be sufficient for long-term animal-health-center/pharmacodynamic
dosage, poor gastrointestinal absorption monitoring. -laboratory
Heparinized tubes (green top) are used for
Drug Effects pharmacodynamic monitoring. AUTHOR: Carrie L. Flint, DVM, DACVP
• Coadministration of phenobarbital, phe- EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
nytoin, trimethoprim-sulfamethoxazole, Relative Cost: $$$$ (peak and trough);
rifampin, famotidine, octreotide, terbinafine, $$$ (single sample)
cyclophosphamide, clindamycin, and aza-
thioprine lower blood cyclosporine levels.

D-Dimer

Definition include local and disseminated intravascular Specimen Collection and Handling
Protein fragments that form from the degrada- coagulation, internal hemorrhage, liver disease, Citrated plasma (blue top tube); it is important
tion of cross-linked fibrin; increased D-dimer chronic kidney disease, and thromboembolic that venipuncture be atraumatic to prevent
concentrations indicate active coagulation and disease. activation of platelets and the coagulation
fibrinolysis. systems; blood and anticoagulant should be
Next Diagnostic Steps to Consider mixed thoroughly immediately after collection.
Physiology if Levels are High Tubes should be filled completely.
D-dimers form when plasmin digests cross- Evaluation of the coagulation system: platelet
linked fibrin; the test is more specific than count, activated partial thromboplastin time Relative Cost: $$
fibrinogen degradation products (FDPs) (aPTT), prothrombin time (PT); consider also
and indicates both thrombin and plasmin thromboelastography (TEG), antithrombin, Pearls
generation. or thrombin time (TT), fibrinogen. Further D-dimers can be increased in patients without
evaluation for thromboembolism if clinical hypercoagulability. Only recommended when
Reference Interval suspicion exists (pp. 842 and 1286) disseminated intravascular coagulation (DIC),
Normal < 250 ng/mL hypercoagulability, or thrombosis is suspected
Lab Artifacts
Causes of Abnormally High Levels • Decrease: inadequately filled tube causes AUTHOR: Deborah G. Davis, DVM, DACVP
Increased fibrinolysis or decreased clearance specimen dilution by anticoagulant EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
of fibrin degradation products by the liver or • Increase: in vitro clot formation
mononuclear phagocytic system; specific causes

Digoxin, Serum Level

Definition Physiology but is mostly excreted by the kidneys. Signs
Cardiac glycoside used in the management of Serum monitoring is recommended due to of toxicity include other arrhythmias, worsening
supraventricular tachycardias, atrial fibrillation, widely variable interpatient pharmacokinetics heart failure, GI signs, and weight loss.
and to a lesser degree heart failure and narrow therapeutic window. There is vari-
able gastrointestinal (GI) absorption following Reference Interval
Synonym oral dosing (presence of food may delay absorp- Therapeutic range (dog and cat): 1.0-2.0 ng/
Digitalis tion). Digoxin undergoes slight metabolism mL. Correlates with clinical effectiveness.

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