ADMINISTRATION ROUTES:
IV, PO
ALTERNATIVE NAMES:
Phytomenadione, Konakion
ICU INDICATIONS:
- Correction of elevated INR due to administration of warfarin or liver impairment
PRESENTATION AND ADMINISTRATION:
IV:
- 2 mg in 0.2 mL vials
- 10 mg in 1 mL vials
Usually administered in ICU by direct IV injection. Administer undiluted by very slow IV push over at least 30 seconds either direct or, where appropriate, into the lower section of an infusion set of a continuous infusion of Normal saline or 5% glucose. Rapid administration can cause back or chest pain, or dyspnoea.
Compatible when injected into the tubing of a continuous infusion of: 5% glucose, 0.9% saline. Store at room temperature.
PO:
Konakion 10 mg tablets (white to yellowish)
DOSAGE:
See APPENDIX 2: Warfarin reversal guidelines
IV/ PO:
0.5 - 10 mg
Avoid large doses if ongoing anticoagulation is required.
DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:
Dose as in normal renal function
DOSAGE IN PAEDIATRICS:
IV/ PO:
0.1 mg/kg to maximum 5 mg
CLINICAL PHARMACOLOGY:
Vitamin K is an essential cofactor for a microsomal enzyme that catalyses the post- translational carboxylation of multiple glutamic acid residues in inactive hepatic precursors of factors II, VII, IX, and X. The resulting gamma-carboxyglutamic acid residues convert the precursors into active coagulation factors that are subsequently secreted by liver cells into the blood. Warfarin prevents reductive metabolism of inactive vitamin K to the active form, so produces biologically inactive factors VII, IX, X, prothombin, protein C & S. Vitamin K exists in two forms: K1 (in food, high in leafy green vegetables) & K2 (produced by intestinal bacteria).
Vitamin K has an action of onset between 1 - 2 hours (IV) and 6 - 10 hours (PO). Peak effects occur within 12 - 48 hours. The IV route has faster onset, but both will have pro-coagulant effects at 24 - 72 hours.
CONTRAINDICATIONS:
- Hypersensitivity to vitamin K
WARNINGS:
If the patient is actively bleeding, whole blood or component therapy should be given, in addition to vitamin K. The time required to synthesise vitamin K-dependent clotting factors (hours) means that vitamin K administration alone is inadequate.
Repeated large doses of vitamin K are not warranted in liver disease if the response to initial use of the vitamin is unsatisfactory. Failure to respond to vitamin K may indicate that the condition being treated is inherently unresponsive to vitamin K.
PRECAUTIONS:
General:
Allergic reactions can occur with IV administration
Laboratory Tests:
INR monitoring to establish efficacy of reversal
Drug/Laboratory Test Interactions:
See Important Drug Interactions in ICU
IMPORTANT DRUG INTERACTIONS IN ICU:
Temporary resistance to prothrombin-depressing anticoagulants may result, especially when larger doses of vitamin K are used. If relatively large doses have been given, it may be necessary when reinstituting anticoagulant therapy to use larger doses of the prothrombin-depressing anticoagulant, or to use one which acts on a different principle, such as heparin.
ADVERSE REACTIONS:
General:
Transient flushing sensations and peculiar sensations of taste have been observed, as well as rare instances of dizziness, rapid and weak pulse, profuse sweating, brief hypotension. The possibility of allergic sensitivity, including an anaphylactoid reaction, should be kept in mind.
Respiratory:
Dyspnoea
Local:
Pain, swelling, and tenderness at the injection site may occur