Dosage, Absorption, and Administration of Eye Drops in Children
Caution is required in the application of topical ocular medications in children, especially in infants. It has been suggested that the estimated required topical dosage from birth to approximately age 2 years is approximately one-half the adult dose; at age 3 years, two-thirds of the adult dose should give equal drug concentrations, and after 3 years of age, the adult dose can be used for practical purposes. Systemic absorption carries a much greater risk in infants. The smaller average blood volume of the neonate and other factors lead to a much higher serum concentration of absorbed medicationsup to 20-fold more. Systemic absorption occurs via the conjunctiva, oropharynx, gastrointestinal system and skin (secondary to overflow from the eye). Without punctal occlusion, as much as 90% of an eye drop may be absorbed by the nasal mucosa.[2,4] Percutaneous drug absorption in newborns, especially premature infants, is much greater than in adults. Other factors increasing drug absorption in newborns include the thin keratin layer of infant eyelids, decreased tear production, and a high incidence of nasolacrimal duct obstruction. In addition, metabolism varies with age and body size; immaturity of neonatal metabolic enzymes slows clearance of drugs by up to six-fold. Steroids and nonsteroidal anti-inflammatory agents are eliminated by the glucoronidation pathways, which do not fully mature until the third to fourth year of life, while elimination of sulfonamides is decreased in infants by immature hepatic acetylation pathways. Other factors that affect drug distribution are reduced plasma-protein binding and the presence of less adipose tissue. As a result, for any given total drug concentration reported, there is a greater percentage of free drug present in the neonate. Renal function is also decreased in the newborn infant due to decreased renal blood flow, decreased kidney size, and reduced tubular function. Glomerular filtration rate is lower than in adults, decreasing the rate of elimination of drugs, such as aminoglycosides and vancomycin, and drugs that are weak acids, such as penicillins, sulfa drugs, and cephalosporins.
There are some techniques that may facilitate the administration of eye drops to young children. Caregivers should be instructed to give only a single drop at a time. When a child is uncooperative, parents can be taught to immobilize the child in order to place a single drop in the conjunctival cul-de-sac. An alternative method is to apply one to two drops on the inner canthus of the closed eye while the patient is supine. When the eye is opened, some of the drop enters the eye, and the excess medication is wiped from the skin with a tissue. In one study, administration of cyclopentolate with this technique was found to cause no increase in systemic absorption or side effects. Punctal occlusion with a finger for 3-4 minutes after application can slow systemic absorption and lower toxicity by up to 40%.[9,10] Any excess overflow should be immediately cleaned from the face.
Compr Ophthalmol Update. 2005;6(2):85-101. © 2005 Comprehensive Ophthalmology Update, LLC
Cite this: Ophthalmic Medications in Pediatric Patients - Medscape - Mar 01, 2005.