Hydroxycobalamin Flashcards
What class of drugs does Hydroxocobalamin belong to?
parenteral vitamins, minerals and nutrition hematinics vitamin B complex nutritional support anti-anaemic agents
What are other drugs which belong to the same calss as hydroxocobalamin?
cyancobalamin injection follinic acid glucose saline infusion kabiven ascorbic acid injection
What is hydroxocobalamin indicated for?
pernicious anaemia
other macrocytic anaemias without neurological involvement
prophylaxis of macrocytic anaemias
tobacco amblyopia
leber’s optic atrophy
cyanide poisoning (emergency)
What is the dose of hydroxocobalamin used in pernicious and other macrocytic anaemias?
if there is no neurological involvement:
IM injection initially 1mg 3x/week for 2 weeks, then 1mg every 3 months (adult)
If there is neurological involvement
IM injection initially 1mg on alternate days until no further improvement, then 1mg every 2 months (adult)
For prophylaxis of macrocytic anaemias assoc. with B12 deficiency,
IM injection 1mg every 2-3 months (adult)
What is the mechanism of action of hydroxocobalamin?
The cobalamins are the 4 major forms in which Vitamin B12 exists in.
Hydroxocobalamin acts as a precursor of 2 coenzymes: coenzyme B12 and methylcobalamin both of which are involved in fat, carbohydrate and protein metabolism.
Coenzyme B12 is required for the conversion of methyl malonate to succinate (which is necessary for the production of haemoglobin).
B12 is also involved in the maintenance of sulphydryl groups in reduced form. Deficiency results in decreased amounts of reduced SH content of RBC and liver cells.
Methylcobalamin is required for the conversion of homocysteine to methionine, which is required for the mtabolism of folic acid
What are the main PK and PD parameters of hydroxocobalamin?
PK:
Cobalamins are absorbed in the lieum and stored in the liver, and continuously undergo enterhepatic recirculation
Part of a dose is excreted in the urine most of it within the first 8 hours.
They can diffuse across the placenta
metabolism is primarily hepatic
half life approx 6 days
What is hydroxocobalamin?
synthetic injectable form of vitamin B12
What are the precautions associated with hydroxocobalamin use?
do not give before diagnosis is fully established. Not for IV admin suspected cobalamin sensitivity (consider administering an ID test dose) infection uraemia folic acid Fe deficiency treatment failure polycythaemia vera mask subacute spinal cord degeneration folate deficient mgaloblastic anaemia intesive megaloblastic anaemia treatment pregnancy lactation
What are the contraindications of hydroxocobalamin use?
hypersensitivity to cobalt
treatment of megaloblastic anaemia of pregnancy
hypersensitivity to any ingredient of the preparation
What are the adverse reactions associated with hydroxocobalamin use?
sensitisation to hydroxocobalamin (rare). May manifest as itching, exanthema, chills, fever, hot flushes, nausea, dizziness, anaphylaxis
nuasea headache dizziness fever
hypokalaemia, thrombocytosis during inital treatment
chromaturia
What are the drug interactions associated with hydroxocobalamin use?
antibacterials: response to hydroxocobalamin is reduced by chloramphenicol
What are the alarm bells associated with hydroxocobalamin use?
some reports of cardiac arrhythmias secondary to hypokalaemia during initial treatment.
doses > 10μg/day may produce a haematological response in patients with folate defiicency.
establish baseline levels for haematological paramters and plasma levels of cobalamin before commencing treatment
What should be monitored with hydroxocobalamin use?
monitor the response of hydroxocobalamin therapy at frequent intervals particularly in the first few weeks of treatment and thereafter at less frequent intervals.
