Chapter 15 Marini Pharmacotherapy

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CHAPTER 15 • Pharmacotherapy

throughout the day when using the enteral route. For example, if the patient was taking metoprolol succinate 50 mg daily, it would be more appropriate to use metoprolol tartrate 25 mg twice daily if given via the enteral route. If there is any doubt whether or not a medication can be crushed and given via an enteral route, it is best to either consult a “do not crush” list or your clinical pharmacist. Although interactions between medications and nutrients have been appreciated for years, specific recommendations on how to administer the major- ity of medications to patients receiving continuous enteral nutrition are lacking. If possible, either a nutritionist or pharmacist should be reviewing appro- priateness of medications for enteral administration. Sublingual/Buccal Administration When enteral drugs cannot be given or are contra- indicated, sublingual or buccal administration may be an option. Only minute quantities of drug are absorbed across intact oral epithelium; therefore, an effective sublingual/buccal drug must be potent and lipid soluble. These methods of administration offer the advantages of quick absorption and avoidance of first-pass metabolism but are disadvantageous because they may irritate the oral mucosa, can only be given in small quantities or in an expensive oral disintegrating tablet, and only constitute a small percentage of drugs. Nitroglycerin is probably the most common sub- lingual formulation given. If swallowed and absorbed enterally, nitroglycerin is rapidly eliminated by first- pass metabolism, but because drugs absorbed from the sublingual space drain directly to the superior vena cava, such first-pass metabolism is bypassed, increasing bioavailability. Another example of a sublingual formulation is atropine, which is often

given to help handle secretions when patients are transitioned to end-of-life care. Although scopol- amine patches may also be given for this indica- tion, atropine is often more desirable because of the more rapid onset. Risperidone, olanzapine, and other selected drugs with useful ICU applications may occasionally be available for delivery in this fashion. Rectal Administration Rectal administration of certain drugs can occa- sionally be useful in children, combative patients, patients with problematic venous access, refractory vomiting, and ileus. Hepatic first-pass metabolism is less extensive with rectally administered drugs than with orally administered ones, but it is still sig- nificant. Unfortunately, rectal administration some- times results in erratic and incomplete absorption and therefore is less desirable than either oral or parenteral dosing. Rectal dosing is best confined to sedatives (e.g., diazepam for seizures), antiemetics (e.g., promethazine), antipyretics (e.g., acetamino- phen), and laxatives (e.g., glycerin). SUGGESTED READINGS Beale RJ, Hollenberg SM, Vincent JL, Parrillo JE. Vasopressor and inotropic support in septic shock: an evi- dence-based review. Crit Care Med. 2004;32:S455-S465. Dhand R, Tobin MJ. Inhaled bronchodilator therapy in mechanically ventilated patients. Am J Respir Crit Care Med. 1997;156:3-10. Dodou K. Intrathecal route of drug delivery can save lives or improve quality of life. Pharm J. Posted online Oct. 31, 2012. Verbeeck RK. Pharmacokinetics and dosage adjustments in patients with hepatic dysfunction. Eur J Clin Pharmacol. 2008;64:1147-1161. WilliamsNT.Medicationadministrationthroughenteralfeed- ing tubes. Am J Health Syst Pharm. 2008;65:2347-2357.