HISTAMINE-RECEPTOR ANTAGONISTS AND LIPID STABILITY IN TOTAL NUTRIENT ADMIXTURES

Drug stability and compatibility studies should be performed for all m edications added to total nutrient admixtures (TNAs) before administra tion to patients. The stability of TNA components will vary depending on product selection and final concentrations. This variability prohib its generalizing published study results generically to TNAs containin g untested products or combinations. Histamine receptor antagonists (H -2RAs) are commonly administered by continuous infusion via nutrient s olutions. When the delivery vehicle is a TNA, comparative stability an d compatibility studies performed under similar test conditions are la cking. The stability of marketed parenteral H-2RAs and of the investig ational H2RA, nizatidine was analyzed in TNA solutions containing eith er Liposyn II or Intralipid at differing concentrations. All H-2RAs re mained at more than 90% of initial concentration at 24 hours. After 48 hours, only ranitidine concentrations fell to less than 90% in all st udy solutions. Each TNA containing an H-2RA was within pH stability ra nges for lipid products, and no change in particle size was detected d uring the 48-hour period. This is the first report determining H-2RA c ompatibility and stability in TNA solutions with both 3% and 5% Intral ipid and Liposyn II and using similar methodology for all standard H-2 RA concentrations. Results suggest that these drugs are stable for 24 hours in TNAs containing either lipid product. Beyond this time, admin istration of ranitidine may be unreliable because of poor stability un der the conditions tested.