PEBC Drug Dispensing and Compounding Flashcards

A pharmacist is compounding a 2% lidocaine HCl topical gel using a carbomer 940 base. The final preparation is adjusted to pH 6.0 using triethanolamine. Which of the following accurately describes the impact of this pH on lidocaine's physicochemical behavior in the gel?

Answer: At pH 6.0, lidocaine is predominantly ionized (pKa 7.9), reducing membrane permeability but improving aqueous solubility within the base

Lidocaine has a pKa of approximately 7.9. At pH 6.0, which is nearly 2 units below the pKa, the Henderson-Hasselbalch equation predicts that approximately 98–99% of lidocaine is in the ionized (protonated) cationic form. This ionized form is more water-soluble and less membrane-permeable than the free base. While ionization reduces transcutaneous penetration, it improves stability and solubility within an aqueous-based carbomer gel. The carbomer/triethanolamine system affects viscosity and pH, not lidocaine's pKa. Lidocaine is an amide, not an ester, so hydrolysis concern does not apply.

A prescription requires a 240 mL oral suspension of metronidazole 50 mg/mL using commercially available 250 mg/5 mL powder for oral suspension. During compounding verification, the pharmacist calculates the quantity of powder needed. What volume of reconstituted commercial suspension (at 50 mg/mL) would be required, and what is the key stability concern specific to this formulation when stored at room temperature?

Answer: 240 mL is required; the key concern is microbial growth due to the aqueous vehicle, necessitating a 14-day BUD at room temperature

The commercial product provides 250 mg per 5 mL = 50 mg/mL. To prepare 240 mL at 50 mg/mL, the total metronidazole needed is 240 × 50 = 12,000 mg. At 50 mg/mL from the commercial suspension, 12,000 ÷ 50 = 240 mL of reconstituted suspension is required. The concentration matches directly (50 mg/mL = 50 mg/mL), so the full 240 mL volume of the reconstituted product is the starting material. The critical stability concern for compounded aqueous oral suspensions is microbial contamination; USP and NAPRA guidelines support a 14-day beyond-use date at room temperature for water-containing oral formulations without preservative testing. Metronidazole is light-sensitive, but the primary BUD driver in aqueous compounded preparations is microbial risk.

Under NAPRA's Model Standards for Pharmacy Compounding of Non-Sterile Preparations, a pharmacist receives a prescription for a compound that requires a controlled drug (Schedule I under the CDSA). Which of the following statements correctly identifies a compounding-specific regulatory obligation that does NOT apply to commercially available Schedule I products dispensed in their original manufactured form?

Answer: The compounded preparation containing the controlled substance must be assigned a lot number and a beyond-use date, and full compounding records must be retained as per provincial standards

When a controlled substance (CDSA Schedule I) is used in non-sterile compounding, the pharmacist must maintain a complete compounding record (master formula, compounding log) that includes the lot number, quantity of controlled substance used, BUD, and final yield. These records must be retained per provincial pharmacy standards (typically 10 years in most provinces, but this varies). This record-keeping obligation specific to compounding goes beyond what is required when simply dispensing a commercially available Schedule I product. Option A misrepresents the retention period as a compounding-specific universal requirement across Canada. Option C is incorrect — there is no DEA in Canada; Health Canada oversees CDSA, and a separate compounding licence is not required beyond the pharmacy's existing licence. Option D is incorrect — pharmacists may use commercially available Schedule I products as source materials for compounding in some jurisdictions.

A pharmacy receives a verbal order from an emergency department physician for morphine sulfate 1 mg/mL oral solution, 100 mL, for a pediatric inpatient. The pharmacy does not stock this concentration and must compound it using morphine sulfate 20 mg/mL oral concentrate. During the compounding process, what is the MOST critical risk management step specific to this high-alert preparation, beyond standard calculations?

Answer: Performing an independent double-check of all calculations and measurements by a second pharmacist or regulated pharmacy technician before dispensing

Morphine sulfate oral solutions are classified as high-alert medications due to their high potential for harm from dosing errors, particularly in pediatric patients. The 20-fold concentration difference between the source (20 mg/mL) and the target (1 mg/mL) represents a significant dilution requiring a 1:19 ratio — errors in this step could result in a 20-fold overdose. ISMP Canada and NAPRA standards mandate an independent double-check (IDC) — a second regulated professional independently performing and verifying the calculation and measurement — as the most critical safeguard. Option B is incorrect because the compound requires its own unique identifier, not the source product's DIN. Option C is incorrect because 'DILUTE BEFORE USE' is inappropriate for a final compounded product ready for administration. Option D is clinically and logistically incorrect; oral morphine is appropriate for pediatric inpatients and commonly compounded.

A pharmacist is preparing a compounded 0.5% betamethasone valerate in a pluronic lecithin organogel (PLO gel) base for transdermal delivery. The prescribing physician requests the preparation be formulated without preservatives. According to USP and NAPRA compounding standards, what is the appropriate beyond-use date (BUD) for this preparation, and what additional testing consideration is uniquely triggered by the absence of a preservative?

Answer: BUD of 90 days at room temperature; antimicrobial effectiveness testing (AET) is required before assigning a BUD beyond 30 days if no preservative is present

Under USP (2023 revision) and NAPRA's Model Standards, non-sterile compounded preparations are categorized by compounding conditions. A Category 2 preparation (compounded for patient use in controlled conditions) without antimicrobial preservatives may be assigned a BUD of up to 90 days at room temperature — provided that stability data support this. Critically, when no preservative is intentionally added, USP triggers a requirement for antimicrobial effectiveness testing (AET per USP ) if a BUD beyond 30 days is desired for water-containing or emulsion-type preparations. PLO gel contains water in its internal phase, making microbial contamination a real risk. The poloxamer 407 in PLO gel does not have intrinsic antimicrobial activity sufficient to meet USP criteria — this is a common misconception. Single-use containers reduce contamination risk but do not exempt preparations from AET requirements.

During a prescription transfer, a pharmacist in British Columbia receives a partially filled prescription for hydromorphone 2 mg tablets (30 tablets dispensed, 60 remaining). The original pharmacy is in Alberta. The patient states the original pharmacist verbally authorized the transfer. Which of the following statements MOST accurately reflects the legal obligations governing this scenario under federal CDSA regulations and applicable provincial standards?

Answer: Prescription transfers for narcotics (Schedule I CDSA) are prohibited under federal law regardless of provincial authorization — the pharmacist must direct the patient to obtain a new prescription

Under Canada's Narcotic Control Regulations (NCR), a subset of the CDSA, narcotic prescriptions (including hydromorphone, which is a Schedule I narcotic) cannot be transferred between pharmacies. This is a federal prohibition — unlike prescriptions for non-narcotic drugs, which may be transferable under provincial pharmacy legislation. The patient must return to the original prescriber for a new prescription or have the original prescriber send a new written/faxed/electronic prescription to the new pharmacy. Option B describes a process that may apply to non-narcotic controlled substances (e.g., under the Benzodiazepines and Other Targeted Substances Regulations) but is not permitted for narcotics. Option C is incorrect — hydromorphone is definitively a Schedule I narcotic under the NCR. Option D conflates procedural requirements that may apply to other drug schedules.