NOVEMBER 01, 2005
Martin A. Erickson III, RPh

Pharmacists engage in problem solving on a daily basis, consulting with prescribers about therapeutic alternatives, with patients about medication administration, side effects, dosing, etc, and with each other about dispensing issues.

Compounding pharmacists are especially familiar with this role, since every compounded prescription is tailored to the specific needs of a patient, in consultation with the prescriber.

Often, professional judgment is the only source on which to draw when solving compounding problems. In such cases, literature searches, bioavailability curves, and other hard data with cited references are inadequate for the purpose. The pharmacist must be willing to synthesize, conclude from his or her background, and confidently assert those conclusions to provide the best result for the patient. This month, we provide a brief example of the sort of analysis in which the compounding pharmacist must engage to practice our profession effectively.

Q: We are having difficulty in preparing a solution of phenobarbital for use in the neonatal department. The only forms of phenobarbital that we have are tablets and ampules. We get an amount of crystals on the walls of the bottle after 3 days. We use acacia as a suspending agent. Can you suggest anything?

A: Whether you use the ampules or the tablets as the source for an active drug, check the excipient list in the prescribing information: 1 or more may be interacting with the acacia. You might try to obtain the bulk powder, if such is the case. Rather than using acacia as a suspending agent (unless the tablets contain acacia, which is unlikely), you might try 1% methylcellulose. Or, checking the tablet excipients, you may find sufficient suspending agent (hypromellose, carboxymethylcellulose, or other). In that case, allowing the tablets to disintegrate in syrup may supply sufficient suspending agent.

An additional complication here is the pH/polar sensitivity of acacia. The characteristic color of the acacia may indicate the composition of the crystalline accumulation.

Mr. Erickson is director of professional affairs at Gallipot Inc.

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