Hospital Pharmacy · Short notes

Sterile Compounding and IV Admixtures: Short Notes & Cheat Sheet

Aseptic technique, cleanrooms and laminar-flow cabinets, TPN, IV incompatibilities, cytotoxic handling and infusion calculations.

Attempt Sterile Compounding and IV Admixtures MCQs

Short notes

Read these before you attempt the topic's MCQs.

Preparing an IV admixture aseptically

Every step protects either the product (sterility) or the operator (hazardous drugs), and some protect both.

Environment

Sterile preparations are made in an ISO class 5 area (a laminar airflow workbench or biological safety cabinet), inside an ISO class 7 buffer room with an ISO class 8 ante-room.
HEPA filters remove at least 99.97% of particles of 0.3 µm.
Horizontal laminar-flow workbenches protect the product and are used for non-hazardous drugs.
Cytotoxic and other hazardous drugs are prepared in a vertical-flow biological safety cabinet (class II) or isolator, which protects the operator too, ideally in a negative-pressure room.
Work at least 15 cm (6 inches) inside the hood and never block the airflow between the filter and critical sites.

Total parenteral nutrition

TPN provides dextrose, amino acids, lipid emulsion, electrolytes, vitamins and trace elements.
Calcium and phosphate can precipitate. Add phosphate early and calcium near the end, mixing between additions.
Lipid emulsions can crack when too many divalent cations are present.
3-in-1 admixtures (with lipid) are given through a 1.2 µm filter; 2-in-1 (lipid-free) through a 0.22 µm filter.

Incompatibilities and hazards

Phenytoin precipitates in dextrose, so it is given in saline. Conventional amphotericin B precipitates in saline, so it is given in dextrose 5%.
Ceftriaxone must not be mixed with calcium-containing solutions.
Glyceryl trinitrate, diazepam and insulin can be lost by adsorption onto PVC bags and tubing.
Sodium nitroprusside and amphotericin must be protected from light.
Cytotoxic handling: chemotherapy-tested double gloves, gowns, closed-system transfer devices, a spill kit and labelled cytotoxic waste.

Cheat sheet

High-yield facts in one place. Cover the right-hand column and test yourself.

Diluent rules

Drug	Diluent / precaution
Phenytoin	Normal saline only
Amphotericin B (conventional)	Dextrose 5% only; protect from light
Ceftriaxone	No calcium-containing fluids
Nitroprusside	Dextrose 5%; protect from light
Glyceryl trinitrate	Non-PVC bags and sets
Potassium chloride	Always diluted; never IV bolus

Infusion formulas

Calculation	Formula
Rate (mL/h)	Volume (mL) ÷ time (h)
Drops per minute	Volume (mL) × drop factor ÷ time (min)
Macro-drip set	Usually 20 drops/mL
Micro-drip set	60 drops/mL
Dose rate	mg/h = mL/h × concentration (mg/mL)

Memory aids

Phenytoin loves Salt, Ampho loves Sugar: Phenytoin goes in saline; conventional amphotericin B goes in dextrose.

Exam traps

A horizontal laminar-flow bench blows air towards the operator, so it must never be used for cytotoxics.
Lipid-containing TPN needs a 1.2 µm filter, not a 0.22 µm filter.
Calcium is added late in TPN compounding to reduce calcium phosphate precipitation.
HEPA filters are rated for 0.3 µm particles, the hardest size to capture.

Revised? Now test yourself.

Attempt the Sterile Compounding and IV Admixtures MCQs while the notes are fresh. Anything you get wrong is saved to your incorrect list for the next revision round.