Dosing During Hemodialysis

Hemodialysis should be considered in addition to treatment with Antizol in the presence of renal failure, significant or worsening metabolic acidosis or a measured plasma ethylene glycol or methanol concentration >50 mg/dL. ¹²

While the use of hemodialysis has been empirically recommended for all patients with plasma ethylene glycol concentrations >50 mg/dL, it has been suggested that such patients may not require hemodialysis if they are asymptomatic with a normal pH and have normal renal function. ^{4, 13, 18}

How Should Antizol Be Dosed During Hemodialysis?

As fomepizole is removed by hemodialysis, patients undergoing this procedure must receive Antizol more frequently. The dosing interval during hemodialysis is every 4 hours. The following schedule shows the timing for Antizol dosing at the start and end of hemodialysis treatment:

At the Beginning of Hemodialysis

• if < 6 hours since the last dose, do not administer;
• if > 6 hours, administer next dose.

During Hemodialysis

• administer every 4 hours.

At the End of Hemodialysis

• if < 1 hour since the last dose and the end of dialysis, do not administer;
• if 1–3 hours since the last dose and the end of dialysis, administer half of the next dose;
• if > 3 hours since the last dose and the end of dialysis, administer the next dose.

Following Hemodialysis

• resume administering every 12 hours.

† Antizol induces its own metabolism, so an increase in the maintenance dose is required after four doses.

Examples of Antizol Dosing in Patients Requiring Hemodialysis

Please note, these examples are intended to illustrate the dosing recommendations provided in the Antizol Package Insert and are not meant to replace consultation with a toxicologist, poison control center or medical information helpline.

Example 1:

A patient received a loading dose of Antizol (15 mg/kg) and 7 hours later it was decided to perform hemodialysis lasting 3.5 hours.

At the beginning of hemodialysis, it was > 6 hours since the last dose of Antizol. Therefore, the patient should receive a maintenance dose of Antizol (10 mg/kg) at the beginning of hemodialysis.

Hemodialysis lasted < 4 hours, so the patient should not receive another dose of Antizol while on hemodialysis.

At the end of hemodialysis, it was > 3 hours since the last dose of Antizol. Therefore, the patient should receive a maintenance dose of Antizol (10 mg/kg).

In the absence of additional hemodialysis, Antizol should be administered every 12 hours at a dose of 10 mg/kg (15 mg/kg after 36 hours) until the ethylene glycol or methanol concentration is < 20 mg/dL and the patient is asymptomatic with normal pH.

Example 2:

A patient received a loading dose of Antizol (15 mg/kg). One hour later, hemodialysis is started which lasts 9 hours.

Antizol is not administered at the beginning of dialysis because it has been < 6 hours since the last dose; however, the dosing schedule must be increased to every 4 hours during hemodialysis.

During the 9 hours of dialysis, the patient receives 2 doses of Antizol (10 mg/kg) after 4 and 8 hours.

At the end of dialysis, it has been one hour since the last dose, so the patient should immediately receive half of the next Antizol dose (5 mg/kg).

In the absence of additional hemodialysis, Antizol should be administered every 12 hours at a dose of 10 mg/kg (15 mg/kg after 36 hours) until the ethylene glycol or methanol concentration is < 20 mg/dL and the patient is asymptomatic with normal pH.