Thursday, October 11, 2012

Diltiazem IV to PO Conversion


This is a question that I’ve gotten a few times over the years.  You’ve got a patient in AFIB that has been rate controlled after a bolus of diltiazem and is now on a diltiazem drip.  The hospital has a policy stating a patient on a diltiazem drip must go to a cluster or ICU bed but the patient could go to a general medical floor, or even go home.  What can be done for the patient?

There is a formula that can be used to estimate the total daily oral dose from an IV diltiazem drip.
Oral dose = {IV drip rate (in mg/hr) x 3 + 3}x10

In general the standard rates for diltiazem convert as follows:
5 mg/hr à 180 mg/day
7.5 mg/hr à 260 mg/day
10 mg/hr à 330 mg/day
15 mg/hr à 480 mg/day

The total daily dose should be divided q6h.  The immediate release dosage form must be used initially and rounding will be necessary since it’s only available as 30mg, 60mg, 90mg and 120mg.  When actually making the switch, give the first oral dose about 1 hour before you plan to stop the drip. After the first hour, slowly titrate down the diltiazem drip by 2.5mg/hr increments until 0. By then the diltiazem should have time to be absorbed and distributed (time to Tmax is approximately 1 to 1.5 hours).

6 comments:

  1. I'm a pharmacy student and I'm researching this exact question! Do you have a reference for this information?

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    1. I unfortunately do not have a reference for that. It was a formula passed down to me from a preceptor. I'm sure if we look at the basic kinetics of diltiazem, it would become evident. Probably a study in there somewhere also...

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  2. I'm a pharmacy student, and I was wondering what is the iv to po conversion of Labetalol and where could I find out other iv to po conversion information?

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  3. I was just having this discussion with one of our attendings. We used to do this all the time when I was a resident and now I see everyone getting put on drips after 1 or 2 bolus doses. I think continuing with PO therapy would be a great option for many of our patients who are stable after a bolus dose of IV diltiazem. It would be great to see it discussed in a reference somewhere, but everything you read is very vague and mostly talks about the initial bolus dose of diltiazem.

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    1. I agree that PO dilt is a great option early on in appropriate patients. I've been searching and digging for some proper referencing and literature for dilt in this setting, but it's surprisingly lacking for how often we use this drug.
      Thanks for the comment!

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  4. This equation is listed in the most current edition of LexiComp's Drug Info Handbook, as are common rate (mg/hr) --> PO conversions (daily dose)

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