9.1 Patient-Specific Parameters: Verifying CSP Orders

9.1 Patient-Specific Parameters: Verifying CSP Orders

A sterile preparation can be perfectly aseptic and still harm the patient if it is the wrong dose, too concentrated for the vein, or unsafe for that patient's kidneys, age or allergies. Domain 2 of the BCSCP outline begins with patient-specific parameters (task 2A1): laboratory values, disease state, age, pathophysiology, anatomy and pharmacology. The sterile compounding pharmacist is the last clinical check before a CSP is made, so order review has to be systematic.

A systematic order-review checklist

BPS gives no reference range table on the exam, so know common normal ranges. Laboratory values appear in the SI units used in U.S. practice.

Renal function: Cockcroft-Gault

$$\text{CrCl (mL/min)} = \frac{(140 - \text{age}) \times \text{weight (kg)}}{72 \times \text{SCr (mg/dL)}} \times 0.85 \text{ (if female)}$$

Worked example: A 70-year-old woman weighing 60 kg has a serum creatinine of 1.2 mg/dL.

$$\text{CrCl} = \frac{(140 - 70) \times 60}{72 \times 1.2} \times 0.85 = \frac{4200}{86.4} \times 0.85 \approx 41 \text{ mL/min}$$

Many renally cleared antimicrobials need an interval or dose change at this level. Check the product labeling or an institutional renal-dosing table.

Weight choices

• Ideal body weight (IBW): men $50 + 2.3 \times$ (inches over 60); women $45.5 + 2.3 \times$ (inches over 60), in kg.
• Adjusted body weight (AdjBW): $\text{IBW} + 0.4 \times (\text{TBW} - \text{IBW})$. It is often used for aminoglycosides in obesity.
• Total body weight (TBW): used for some drugs, such as many vancomycin loading doses, according to guidelines.

Body surface area (BSA) for chemotherapy

$$\text{BSA (m}^2\text{)} = \sqrt{\frac{\text{height (cm)} \times \text{weight (kg)}}{3600}}$$

For a patient 170 cm tall weighing 70 kg: $\sqrt{170 \times 70 \div 3600} = \sqrt{3.31} \approx 1.82\,\text{m}^2$. A dose of 75 mg/m² is therefore about 136 mg. Recalculate BSA-based doses independently and check them against the protocol, including any dose caps and cumulative limits, such as lifetime anthracycline exposure.

Parenteral nutrition order review

• Macronutrients: Check dextrose (glucose infusion rate), amino acids (g/kg/day) and lipids (g/kg/day) against the patient's needs and guidelines. Check triglycerides before and during lipid therapy.
• Electrolytes: Adjust to serum values and to losses such as diarrhea or fistula output, and keep calcium and phosphate within the solubility curve (see 8.3).
• Refeeding syndrome: ASPEN's 2020 consensus on refeeding risk advises, for patients at risk:
  • start cautiously, around 100-150 g of dextrose or 10-20 kcal/kg in the first 24 hours, and advance over several days;
  • give thiamine 100 mg before feeding and daily for 5 to 7 days or longer;
  • check potassium, magnesium and phosphorus before starting and every 12 hours for the first 3 days in high-risk patients, replacing as needed.
• Access: Peripheral PN is limited to about 900 mOsm/L. Higher concentrations need a central line (see 8.1).

Special populations

• Neonates and infants:
  • Use preservative-free products and flushes, because benzyl alcohol can cause gasping syndrome.
  • FDA limits aluminum in large-volume parenterals used in PN to 25 µg/L or less and requires aluminum content on the labels of small-volume products.
  • Calcium-phosphate risk is high when amino acid concentrations are low.
  • Microvolumes need syringes sized to the volume (see 9.4).
• Older adults: Lower clearance, lower muscle mass (serum creatinine can overestimate renal function), and a higher risk of fluid overload.
• Pregnancy: Consider fetal risk from the therapy, and the handling risk for staff who are pregnant or planning pregnancy when HDs are involved. USP <800> requires staff of reproductive capability to confirm in writing that they understand the risks.

Pharmacology-based checks

Check for incompatible Y-site combinations, such as ceftriaxone with calcium-containing solutions in neonates. Check route-specific dose limits, since intrathecal doses are a small fraction of IV doses. Check dose caps, such as vincristine commonly capped at 2 mg per dose in adult protocols, and maximum infusion rates, such as potassium in peripheral lines under institutional policy.