Antinausea Gel Not Absorbed at Therapeutic Levels



DENVER – Compounded ABH gel is widely prescribed for treatment of nausea in the hospice setting. It costs less than $1 per dose. Side effects are rare. And many clinicians swear by its effectiveness, noting that the constituent medications in ABH gel – Ativan (lorazepam), Benadryl (diphenhydramine), and Haldol (haloperidol) – target different mechanisms of nausea.

There is, however, a fly in the ointment ... er, gel.

It turns out that none of the three medications in topical ABH gel are absorbed systemically in anything remotely approaching therapeutic levels, Dr. Devon S. Fletcher reported at the annual meeting of the American Academy of Hospice and Palliative Care Medicine.

"Either ABH gel doesn’t work, or the effect is attributable to placebo, or possibly a nonpharmacologic mechanism is involved, such as stimulation of the P6 acupressure point on the wrist as patients rub the gel in," said Dr. Fletcher of Virginia Commonwealth University, Richmond. "If ABH doesn’t work, using it to treat a symptom leads to unacceptable suffering and unnecessary hospitalizations," she added.

Dr. Fletcher and coworkers measured levels of the three medications contained in ABH gel in six blood samples taken serially in each of 10 healthy volunteers up to 4 hours after they rubbed 1 mL of the gel between their volar wrists for 2 minutes. That’s the standard means of administering the medication, which is self-applied every 4-6 hours in clinical practice. A 1-mL dose contains 2 mg of lorazepam, 25 mg of diphenhydramine, and 2 mg of haloperidol compounded using a popular published formula.

Both lorazepam and haloperidol were undetectable in blood samples at all times in all 10 subjects; the medications never made it past the skin barrier. The highest concentration of diphenhydramine, reached in only a single patient, was 0.3 ng at 4 hours. That translates to 0.0003 mcg/mL, roughly 1/1000th of the therapeutic level, she noted.

The study was undertaken as a prelude to a planned single-center, randomized, placebo-controlled, crossover clinical trial of ABH gel in hospice patients with nausea. Dr. Fletcher and coinvestigators still plan to conduct that trial because ABH gel has never been subjected to a prospective controlled study.

"This is a wake-up call that we need further testing and evaluation before introducing treatments into widespread use," the physician declared.

Several audience members rose to applaud Dr. Fletcher for what they called a long-overdue rigorous look at an extremely popular yet unexamined therapy. One physician said he’d also like to see placebo-controlled studies of phenobarbital and dexamethasone for nausea, as these agents are widely prescribed but lacking in solid data supporting efficacy. He added that his own anecdotal experience with those two drugs as antiemetic agents in the hospice setting has been disappointing.

Dr. Fletcher reported having no financial conflicts.