Considerations in comparing intravenous and intramuscular antibiotics.

With the implementation of prospective payment (e.g. diagnosis-related groups [DRGs] and cost containment efforts, physicians and pharmacists have had to reevaluate current drug delivery systems in the search for the least costly means of administering parenteral products. The following describes a three-phase approach to fully assess relative antibiotic cost and to assess economic efficiencies of intramuscular and intravenous administration of antibiotics. Relative costs of therapy consist of acquisition cost, administration cost and total cost of self-administration. Various intravenous administration systems are described, as are considerations for intramuscular administration. Comparisons are made using intravenous and intramuscular administrations of cefazolin, gentamicin, penicillin and imipenem. Using a 'best case' scenario, the intramuscular route was found to be up to one tenth the expense of the intravenous route in certain instances. Also, the intramuscular route may facilitate early discharge and self-administration in the home. Antibiotics available for intramuscular injection should therefore be considered as an economically efficient alternative to intravenous injections, in appropriate patients.