9.6 Medication Adherence in Home and Outpatient Sterile Therapy

9.6 Medication Adherence in Home and Outpatient Sterile Therapy

When sterile therapy moves home, the pharmacist no longer sees each dose given. Outpatient parenteral antimicrobial therapy (OPAT), home parenteral nutrition, continuous inotropes, pain pumps, self-injected biologics and oral-to-IV chemotherapy regimens all depend on the patient and caregiver. The BCSCP outline lists medication adherence (task 2B3) under therapeutic outcomes and monitoring. Missed or mistimed doses can cause treatment failure, antimicrobial resistance, readmission or line complications.

Key definitions

Measuring adherence for sterile therapies

Objective measures

• Ambulatory pump history logs: Programmable home pumps record doses delivered, pauses, alarms and bolus requests. Review them at each nursing visit or cassette change.
• Dose reconciliation: Compare doses delivered with doses used, and count unused or returned bags and syringes.
• Delivery and refill records: Missed deliveries, or supplies building up in the home, suggest doses are being skipped.
• Clinical markers: Drug levels (for example vancomycin), markers of infection (fever, inflammatory markers), and PN labs (glucose, electrolytes, weight trends).

Subjective measures include patient or caregiver report and structured questionnaires. They are easy to collect but tend to overestimate adherence.

Proportion of days covered (PDC)

$$\text{PDC} = \frac{\text{days with medication available}}{\text{days in the measurement period}} \times 100\%$$

Example: Deliveries covered 26 of the 30 days in a month, so $\text{PDC} = 26 \div 30 = 86.7\%$. That is above the common 80% threshold used to call a patient adherent. The PDC shows supply, not actual use, so pump logs and clinical data are still needed.

Barriers specific to parenteral therapy

How the compounding pharmacist influences adherence

Many adherence problems are solved at the compounding bench:

• Regimen simplification through stability-supported continuous infusions in ambulatory pumps, or combining doses into one reservoir, only when the drug's stability over the full reservoir time and at body-proximate temperatures has been shown.
• Ready-to-use formats, such as prefilled syringes and premixed bags, remove steps where patients make mistakes.
• Delivery schedules and BUDs matched to the patient's routine.
• Clear, consistent labels with the dose, the time and the storage instructions.

Counseling approaches

• Teach-back for every critical step (see 9.3).
• Motivational interviewing: open questions, reflective listening, and bringing out the patient's own reasons to continue.
• Shared decision-making about the schedule and the device.
• Structured follow-up: a call within 24 to 48 hours of starting home infusion, then at each delivery or visit.
• Caregiver involvement when the patient cannot manage alone.

Closing the loop

Document the adherence findings, the barriers and the interventions. Tell the prescriber and the OPAT or nutrition support team when nonadherence threatens outcomes, for example when antibiotic doses are missed during treatment of endocarditis. Adherence data are also a quality measure, reviewed with readmissions and line infections.

Adherence issues by therapy type

• OPAT antimicrobials: Missed or delayed doses can mean treatment failure in endocarditis or osteomyelitis, and they bring the risk of resistance. Weekly laboratory results, such as blood counts, renal function and vancomycin levels, double as adherence checks.
• Home parenteral nutrition: Skipped or shortened cycles can cause dehydration, electrolyte problems and hypoglycemia after abrupt stops. Review weight, fluid balance and glucose logs with the PN order.
• Continuous inotropes and pain pumps: Interruptions are dangerous. Teach how to handle alarms and bag changes, and give an after-hours number for pump failures.
• Self-injected products (for example low-molecular-weight heparin or biologics): Check injection technique, storage and sharps disposal, and watch for injection-site reactions that lead patients to skip doses.

Warning signs of nonadherence include supplies piling up in the home, missed laboratory draws, repeated unacknowledged pump alarms, deliveries refused or rescheduled, and results that do not fit the prescribed regimen.