The Silent War in Inpatient Pharmacy

Introduction

Much of the public's perception of a pharmacist's role is shaped by their interactions in the ward and at outpatient or community pharmacies.

• However, a significant number of dedicated pharmacists work diligently in inpatient settings, ensuring accurate medication dispensing to hospitalized patients.
• Daily tasks often involve managing medication stock (through floor stock supply and filling medication trolleys) and providing patient counselling, especially in wards without dedicated clinical pharmacists.

Transition From Outpatient Pharmacy

Having transitioned from outpatient to inpatient pharmacy, I personally prefer the latter due to reduced patient-related stress, such as dealing with aggressive patients and dispensing at crowded, noisy counters.

• Unlike outpatient settings with strict waiting time policies and crowded waiting areas, inpatient pharmacy work seems more flexible, but remains demanding.
• When staff are absent or in meetings, we still need to complete tasks timely before the lunch break, so that nurses can serve the next dose as scheduled.

Another significant difference is the complexity of inpatient medication orders.

• Outpatient prescriptions are typically shorter, while inpatient orders can span multiple pages.
• This requires careful attention to detail and significant mental efforts, as pharmacists must identify new or discontinued medications, potential drug interactions and polypharmacy while fulfilling medication orders.
• Long-term patients may have extensive medication charts, adding to the complexity.
• This challenge is less prominent in hospitals with electronic prescription systems.

Oral And IV Doses Are Not Always The Same

While some medications are common to both inpatient and outpatient settings, many intravenous drugs, such as adrenaline, ceftriaxone, cefoperazone, meropenem, and propofol, are primarily used in acute care.

• Also, patient conditions may necessitate higher-than-usual dosages, requiring pharmacists to stay updated on drug information and dosing guidelines.

It is not uncommon to encounter new physicians, particularly recent graduates, who may prescribe oral medications at intravenous dosages and vice versa. For instance,

• Tablet Metronidazole 500 mg TDS
• Metronidazole tablets are only available in 200 mg strength.
• Tablet Cefuroxime 500 mg TDS
• Maximum oral dose of cefuroxime is 500 mg twice daily.
• IV Bromhexine 8 mg BD or 8 mg TDS
• Maximum recommended IV dose is 12 mg/day (i.e. 4 mg TDS).

Confusion in Pediatric Dosing

Pediatric dosing has always been a source of confusion, particularly when relying on various references.

• Recently, I encountered a case involving a 20 kg child prescribed Injection Unasyn 1 g QID.
• After further clarification with prescriber, the prescription aimed to achieve a target dose of 50 mg/kg of the ampicillin component QID, as suggested by Frank Shann's Drug Doses.
• While 20 kg * 50 mg/kg = 1000 mg (or 1 g) seems straightforward, each Unasyn 1.5 g vial contains 1 g of ampicillin and 500 mg of sulbactam.
• Technically, we should administer a full vial of Unasyn 1.5 g, rather than further dilute the two-thirds of the reconstituted volume.
• To minimize medication error, the IV Unasyn should ideally be prescribed as 1.5 g (1 g of amoxicillin component) QID.

This consideration should be extended to other combination antibiotic injections like Bactrim (sulfamethoxazole and trimethoprim), Augmentin (amoxicillin and clavulanate), Tazosin (piperacillin and tazobactam) and Tienam (imipenem and cilastatin).

• For instance, Bactrim injections are typically dosed based on the trimethoprim component.

However, it is crucial to carefully review references to determine whether the recommended dosing range is based on a single ingredient or the entire formulation.

• To illustrate, subject to reference referred, Augmentin 1.2 g injection is dosed at 30 mg/kg of amoxicillin and clavulanate (as suggested in Clavicin 1.2 g injection product leaflet) or 25 mg/kg of amoxicillin component (as recommended in Lexicomp). Regardless of the dosing range employed, the final reconstituted volume calculated remains the same.
• The ratio of amoxicillin to clavulanate in Augmentin 1.2 g injection is 5:1. Therefore, to recalculate the entire formulation dose from amoxicillin component, we can use the formula: 25 mg/kg * 6/5 = 30 mg/kg.

Injectable Drugs

While consideration must be given to the optimal timing of oral medication administration, whether before, with, or after meals, injectable medications necessitate careful selection of the appropriate route, such as in intravenous (IV bolus, slow bolus, infusion), intramuscular (IM), subcutaneous (SC), intrathecal (IT), or others.

• Although certain drugs may be suitable for multiple routes of administration, specific brands may have limitations.
• For instance, lignocaine 2% injection (as depicted in the image below) may be contraindicated for intravenous administration.

To ensure safe and effective adminsitration of injectable drugs, it is important to refer to the product leaflet or an authoritative dilution protocol reference when unsure.

• Some medication need to be given by IV infusion over a certain period.
• To illustrate, IV vancomycin needs to be infused over at least one hour (depending on the dose) because rapid administration may lead to "red man syndrome".
• Potassiumc chloride injection must be diluted before parenteral administration. Undiluted administration or rapid intravenous push may cause fatal cardiac arrest.
• Amphotericin B injection (Amphotret) needs to be protected from direct sunlight and stored at a temperature not exceeding 8˚C, preferably in a refrigerator. The reconstituted solution is stable for up to 7 days when stored at 2-8˚C and protected from light during administration.

Another area where experience is crucial is calculating the required volume for infusion medications like noradrenaline, adrenaline, dexmedetomidine, and dobutamine.

For example, what is the infusion rate in milliliters per hour for dexmedetomidine in a 70 kg patient at a dose of 0.7 mcg/kg/hour? What is the number of vials required for a 24-hour infusion?

• Total dose in micrograms per hour = 0.7 mcg/kg/hour x 70 kg = 49 mcg/hour
• Dexmedetomidine 100 mcg/ml vial is typically diluted in 50 ml of sodium chloride 0.9% to a concentration of 4 mcg/ml before administration.
• Infusion rate = 49 mcg/hour / 4 mcg/ml = 12.25 ml/hour.
• Total volume to be infused in 24 hours = 12.25 ml/hr x 24 hour = 294 ml
• Each vial, when diluted to 50 ml, contains 50 ml of solution.
• Number of vials required = 294 ml / 50 ml/vial = 5.88 vials
• Therefore, approximately 6 vials of dexmedetomidine would be required for a 24-hour infusion in this patient.

Additionally, what are the concentrations of single-strength and double-strength noradrenaline infusions?

• The concentrated noradrenaline solution (typically 1 mg/ml) is diluted in a specific volume of dextrose 5% before administration.
• Single strength: Dilute 1 ampoule (4 mg/4 ml) in 50 ml diluent (0.08 mg/ml).
• Double strength: Dilute 2 ampoule (4 mg/4 ml) in 50 ml diluent (0.16 mg/ml).

Dosage Adjustment

Inpatient settings often require more frequent renal or hepatic dosage adjustment compared to chronic outpatient care, such as those critically ill patients with acute kidney injury.

• A lower-than-usual dosing regimen may suggest renal impairment. For example, IV amoxicillin/clavulanate BD instead of TDS, IV Cefuroxime BD or TDS instead of TDS, IV imipenem BD instead of TDS, and IV piperacillin/tazobactam 4.5 g TDS or 2.25 g QID instead of 4.5g QID.
• For hypoalbuminemic patients (serum albumin ≤25 g/L) with normal renal function, IV ceftriaxone 1 g TDS is the recommended maintenance dose, rather than 1 g BD.

NOTE: Certainly, all speculations about dosage adjustment should be verified with lab test results.

Summary

Pharmacists working in diverse settings, such as inpatient and outpatient pharmacies, develop a comprehensive skill set that benefits both patients and healthcare providers.

• While clinical pharmacists are often recognized for their advanced clinical knowledge and familiarity with local practices, inpatient and outpatient pharmacists possess a unique skill set, honed through daily challenges like rapid medication screening and accurate medication refilling.

Adhering to prescribed medication orders is a straightforward task.

• However, identifying and challenging potential medication errors demands a deep understanding of clinical knowledge and local practices.
• To excel in this complex endeavour, pharmacists must commit to continuous learning.

Remember, all pharmacists play a crucial role in delivering high-quality pharmaceutical services.