Using glargine intravenously for diabetic ketoacidosis
Diabetic ketoacidosis results from prolonged inadequate insulin activity. The main aims of therapy are to supply exogenous insulin, restore hydration status and manage electrolyte disturbances. Ketoacidotic cats usually present severely dehydrated and as such, have reduced absorption from subcutaneous tissue (from reduced blood flow). Until hydration is restored, insulin must be administered either intravenously or intramuscularly.
For many years, the insulin of choice for treating ketoacidosis has been regular insulin due to its rapid onset, potent glucose lowering effect and predictably short duration of action. Glargine has almost identical properties to that of regular insulin when used intravenously (Scholtz et al, 2003). Its actions are so similar that glargine can simply be substituted for regular insulin (for all your current protocols just draw glargine up instead of regular insulin). There are no reported clinical trials in the human literature assessing glargine administered intravenously as it was accepted to have no benefit over regular insulin. Regular insulin is used solely to treat diabetic ketoacidosis and many veterinary clinics chose not to stock it (or use it well after the expiry date) as the disease is seen so infrequently and most of the vials are wasted. Glargine on the other hand, can be used in DKA as well as maintenance therapy and most clinics have it on hand for diabetic cats. We mix glargine with normal saline, hartmann’s or 2.5% glucose solution. It is uncertain how long it will stay active in these solutions so suggest a new solution is made every 24hrs.
Glargine can be administered to ketoacidotic cats by:
- infusing intravenously at a rate of 0.05-0.1 U/kg/hr and rate adjusted to maintain blood glucose between 10-14mmol/L or
- injected s/c at the normal dose rate (0.25-0.5U/kg) as well as 0.5-1U of glargine injected IM or IV
As soon as I have a diagnosis of DKA, I immediately administer 0.5U/kg subcutaneously as well as 1U into the quadriceps muscles. I often administer glargine before I have discussed the diagnosis and treatment plan with owners. If they decide not to treat the cat, little has been lost as the syringes and insulin probably cost the clinic less than $1. I have found most cats require 1U of glargine given IM every 2-4hrs based on glucose concentration. The dosing of glargine IM or IV is continued until hydration is restored and appetite returns, which usually occurs in 1-3 days. Glargine is then injected s/c and dosed as for an uncomplicated cat (see Table 1).
Please note When injected s/c, glargine reacts with the tissue and forms micro-precipitates which are slowly absorbed and is responsible for its long duration of action. Mixing or diluting glargine with any solution inhibits micro-precipitates forming and significantly reduces the duration of action. It is only when using intravenously for treating DKA that it can be mixed with other solutions as a long duration of action is not required.
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