September 2000
IOWA CITY, Iowa - When parents leave the pharmacy with antibiotics for their children, they usually have an oral suspension. But pharmacists may dispense volumes of oral suspension inadequate to complete treatment regimens.
Results of a study conducted in 1996 and 1997 at the University of Iowa Colleges of Medicine and Pharmacy and recently published in Pediatrics indicate that pharmacists often do not dispense volumes adequate to complete treatment regimens, which may lead to the bacteria not being eradicated. Additionally, investigators found potential problems related to medication instructions from the dispensing pharmacist.
Physical characteristics often make dispensed antibiotic suspension volumes inadequate to complete the prescribed treatment course. This is less problematic for penicillin than for trimethoprim-sulfamethoxazole (TMP-SMX), which may vary greatly in texture. The more viscous the oral antibiotic, the greater the chance of running out prematurely because of the medication adhering to the walls of the medicine cup, syringe and medicine bottle.
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While most pharmacies listed directions on medication bottles, they varied in completeness. For example, almost all penicillin prescriptions had refrigeration instructions, but only four pharmacies reminded parents not to refrigerate TMP-SMX. Refrigerating TMP-SMX "makes the medication so thick that you really cut down the likelihood of getting anywhere near adequate duration of treatment," said Lois B. Dusdieker, MD, associate professor of pediatrics at the University of Iowa College of Medicine here. "It's just too thick."
Because of differences in physical characteristics, investigators found that 130 mL, not 100 mL, is needed to complete the 20-dose regimen of TMP-SMX. They also found that a 30-dose regimen of penicillin requires 160.5 mL of antibiotic suspension instead of 150 mL.
"If you write `dispense for a 10-day supply,' your patients are not going to be getting enough of the viscous types of antibiotics," Dusdieker said. "Physicians need to stop, calculate what they think they're going to need and add in that extra percentage on the basis of how thick the medication is, so that the kids get [the amount of medication they will need] dispensed initially. Most families are reluctant to pay the extra expense or have the extra hassle of going back to the pharmacy and waiting two hours to pick up the prescription."
Physicians should ask that a syringe or medication spoon be dispensed to improve accuracy and prevent waste, Dusdieker said. Many pharmacies did this even without it being specified in the prescription.
Reviewing the reasoning for a specific antibiotic, checking for allergies and explaining possible adverse drug reactions and interactions may also be helpful. While most pharmacies asked about allergies, many did not ask about other medical conditions or provide information about adverse events or interactions and contraindications. No pharmacist provided verbal counseling for self-monitoring drug therapy, and none addressed the intended use of the drug or the expected action. Pharmacists also did not explain what should be done in the event of a missed dose.
Researchers studied penicillin as generic penicillin potassium oral suspension (250 mg/5mL) and TMP-SMX as Bactrim (Roche) oral suspension (200 mg SMX and 40 mg TMP/5 mL). Both were written for a specified volume of suspension for each dose and treatment duration. Prescription instructions to the pharmacist specified to "dispense a 10-day supply." Prescriptions were filled in 61 pharmacies in a three-county area. Researchers documented pharmacist instructions/counseling offered or given regarding medications. Thirty-two percent of pharmacists included written instructions, which varied from a few sentences to extensive paragraphs.
Medications were refrigerated until volume analysis was performed. Medication analysis included several steps. First, both prescriptions were removed from the refrigerator. TMP-SMX was allowed to approach room temperature before analysis. Prescription labeling information, including brand or generic name, volume dispensed and prescription information was recorded.
The mean volume of penicillin dispensed was 195 mL, and the mean number of doses was 29.4. Forty-six pharmacies dispensed 30 or more doses. The mean volume of TMP-SMX dispensed was 107 mL, and the mean number of doses was 16.5. No pharmacy dispensed the full 20 doses needed to complete the prescribed treatment course.
Researchers measured the actual volume dispensed using similar techniques parents would normally use at home. The bottle was shaken, and the contents were poured into a graduated cylinder. The total volume was recorded and approximately 10 mL to 15 mL was poured into a 30-mL medicine cup, from which 5 mL was withdrawn using a 6 mL syringe. The dose was discarded and recorded. The remaining suspension was returned to the graduated cylinder, and the medication cup and syringe were rinsed and dried. This was repeated until all medication was used.
For more information:
- Dusdieker LB, Murph JR, Milavetz G. How much antibiotic suspension is enough? Pediatrics. 2000;106(1):e10.
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