Rx Update: June 2004

Potassium Intravenous Administration
Preventing Metformin - Associated Lactic Acidosis

Joan Murhammer, R.Ph., Mary Ross, R.Ph., M.B.A., Kevin Bebout, R.Ph.
Peer Review Status: Internally Reviewed

Potassium Intravenous Administration

Potassium injection may cause pain upon intravenous administration. This pain is a potential warning sign of tissue damage and possible phlebitis or extravasation. Options to decrease pain on administration and potential tissue damage include:

• Use a more dilute solution (e.g., 10 mEq/150 ml, 20 mEq/250 ml, or 40 mEq/1000 ml). Administer the dose in a less concentrated solution (e.g., 40 mEq/1000 ml) via two separate peripheral IVs simultaneously.
• Slow down the infusion rate.
• Co-administer the potassium IV piggyback into an IV maintenance solution (i.e., allow the peripheral maintenance solution to run while administering the potassium IV piggyback); this will further dilute the potassium and decrease vein irritation.
• Administration via a high-flow vein (e.g., femoral vein). Warning: Administration of large amounts potassium through a subclavian, jugular, or right atrial catheter should be done with caution; local potassium concentrations achieved in the heart may become too high and cause serious cardiac arrhythmias.
• Convert the patient to oral potassium therapy.

Lidocaine should not be added to potassium infusions to minimize pain because lidocaine has the potential to mask infection or vein injury that presents as phlebitis, mask the symptoms of a potassium overdose by preventing the burning sensation, and increase the risk of medication error. Refer to Nursing Policy 08.023 for further information on potassium IV administration in adult patients.

Preventing Metformin - Associated Lactic Acidosis

Metformin can cause a rare, but serious, metabolic complication called lactic acidosis. When lactic acidosis occurs, it is fatal in approximately 50% of cases. Lactic acidosis is characterized by elevated blood lactate levels, decreased blood pH, electrolyte disturbances with an increased anion gap, and an increased lactate/pyruvate ratio. Symptoms of lactic acidosis include malaise, myalgias, increasing somnolence, abdominal symptoms, respiratory distress, hypothermia, hypotension, and resistant bradyarrhythmias. Reduced kidney function is the single most important risk factor for developing lactic acidosis in patients taking metformin.

Intravascular contrast studies with iodinated materials (e.g., intravenous urogram, intravenous cholangiography, angiography, and computed tomography [CT] scans with contrast materials) can lead to an acute decrease in renal function and have been associated with lactic acidosis in patients receiving metformin. Therefore, in patients in whom any such study is planned, metformin should be stopped before or at the time that a patient has a radiology study using an iodinated contrast media. After the radiology study, metformin should be withheld for at least 48 hours and should only be re-instituted after confirming that renal function is normal.

Metformin should also be temporarily suspended for any surgical procedure (except minor procedures not associated with restricted intake of food and fluids) and should not be restarted until the patient's oral intake has resumed and renal function has been evaluated as normal. Metformin should also be promptly withheld in the presence of any condition associated with hypoxemia, dehydration, or sepsis.

Metformin is available as single-ingredient products (Glucophage^®, Glucophage XR^®, Riomet^®, Fortamet^®); and in combination products with glyburide (Glucovance^®), glipizide (Metaglip^®), and rosiglitazone (Avandamet^®). Patients who are hospitalized or undergoing surgical or radiologic procedures should be carefully monitored for any changes in renal function status while they are on metformin therapy.

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