PEBC Drug Dispensing and Compounding Flashcards

A pharmacist receives a prescription for a pediatric patient requiring a 2 mg/mL oral suspension of amlodipine. The pharmacist has amlodipine 5 mg tablets available. When compounding this preparation, which beyond-use date (BUD) is MOST appropriate according to USP guidelines for a non-sterile aqueous liquid preparation made from commercial tablets?

Answer: 30 days at room temperature or refrigerated

According to USP , non-sterile aqueous preparations compounded from manufactured solid dosage forms are assigned a BUD of 30 days, stored at room temperature or refrigerated, unless stability data support a longer period. The 14-day BUD applies only to water-containing formulations compounded from non-sterile bulk ingredients (non-aqueous), or where specific instability is known. Six months and 90 days require documented stability studies.

A pharmacist is filling a prescription for warfarin 7.5 mg tablets. The dispensary only has 5 mg and 10 mg warfarin tablets. The prescriber is unavailable, and the patient states they have been on this dose for years. Which action BEST reflects the pharmacist's legal and professional obligations under Canadian pharmacy practice?

Answer: Contact the prescriber to obtain a verbal order for the alternative tablet strengths and document the intervention

The pharmacist must not alter a prescription without prescriber authorization. The correct action is to contact the prescriber for a verbal order authorizing an alternative dispensing strategy (e.g., alternating 5 mg and 10 mg on alternating days). Simply counseling the patient to split tablets without prescriber involvement, or refusing outright when a clinically sound solution exists, fails the duty of care. Proper documentation of the verbal order is mandatory.

When performing an osmolarity check on a compounded parenteral nutrition (PN) admixture intended for peripheral venous administration, the calculated osmolarity is 950 mOsm/L. Which statement regarding this preparation is MOST accurate?

Answer: It exceeds the generally accepted threshold of 900 mOsm/L for peripheral PN and should be reformulated or administered centrally

The generally accepted osmolarity limit for peripheral PN administration is ≤900 mOsm/L (some references cite 850–900 mOsm/L) to minimize the risk of phlebitis and thrombosis. A value of 950 mOsm/L exceeds this threshold, so the preparation should be reformulated to reduce osmolarity or switched to a central venous access route. Infusion rate does not mitigate the osmolarity-driven vascular damage.

A pharmacist compounds a 0.1% (w/v) tacrolimus ointment using tacrolimus 1 mg/g commercially available ointment as the starting material, diluted with white petrolatum. The final preparation is placed in a pre-labelled dispensing jar. Which compounding error is MOST likely present in this scenario?

Answer: Diluting a manufactured product to produce an unapproved concentration without adequate stability data or a documented compounding rationale

Diluting a Health Canada–approved commercial product (tacrolimus 0.1% ointment is already approved; tacrolimus 1 mg/g = 0.1% w/w) to create a different concentration constitutes compounding of a preparation that mimics a commercially available product — which is restricted under NAPRA guidelines and provincial regulations unless a documented clinical justification exists and stability of the diluted preparation is established. White petrolatum is a compatible ointment base for tacrolimus. Class II BSCs are required for hazardous sterile preparations, not ointments. No absolute maximum concentration for topical tacrolimus applies here.

A pharmacist receives a faxed prescription from a prescriber in another province for a Schedule II controlled substance (opioid). The pharmacist is practicing in Ontario. Which of the following MOST accurately describes the validity of this prescription?

Answer: The prescription is invalid; Ontario requires controlled substance prescriptions to be written by prescribers licensed in Ontario on provincially approved forms

Controlled substance prescriptions are governed by both the federal Controlled Drugs and Substances Act (CDSA) and provincial/territorial regulations. In Ontario, the Drug and Pharmacies Regulation Act and Ontario Regulation 264/16 require that prescriptions for controlled substances be issued by practitioners authorized to prescribe in Ontario. A prescriber licensed only in another province is generally not authorized to prescribe controlled substances in Ontario. The DEA number is a US designation and has no standing in Canada.

During final verification of a compounded sterile preparation (CSP), the pharmacist notices a fine white precipitate in the IV bag. The admixture contains calcium gluconate, magnesium sulfate, and potassium phosphate in dextrose 5% in water. Which ion interaction MOST likely accounts for this precipitate, and what should the pharmacist do?

Answer: Calcium–phosphate precipitation; reject the admixture and recompound with corrected order of addition and concentration limits

Calcium phosphate precipitation is one of the most clinically dangerous incompatibilities in IV compounding. When calcium and phosphate concentrations exceed solubility limits — influenced by pH, temperature, amino acid concentration, and order of addition — calcium phosphate crystals form and can cause fatal pulmonary emboli if administered. The correct response is to reject the preparation entirely, never to filter it (filters can miss microcrystals) or warm it. Recompounding requires adjusting concentrations and following the correct order of addition (phosphate early, calcium late).