Section 33.6: Specialty Populations: OB & Peds

Part 1: The World of Obstetrics (OB)

33.6.1 The “Why”: Two Patients, One Plan

Stepping onto a Labor & Delivery (L&D) unit is to enter a unique clinical universe governed by a single, immutable principle: every decision must account for **two patients**. The mother and the fetus are a single, integrated physiological unit, and every medication administered, every order verified, carries the weight of this dual responsibility. The physiological transformations of pregnancy are profound and dramatically alter pharmacokinetics. A pregnant woman’s plasma volume can increase by 50%, her cardiac output rises, and her renal clearance is significantly enhanced. These changes can alter the volume of distribution and elimination of drugs, requiring dosing adjustments that would be unheard of in a non-pregnant patient.

The order sets used in obstetrics are therefore designed with an unparalleled focus on safety, utilizing standardized concentrations, smart pump technology, and explicit monitoring protocols to navigate the razor-thin therapeutic windows of high-alert medications. As the pharmacist, you are the ultimate guardian of this dyad. Your role is to be a master of the few, but incredibly potent, medications used in L&D. You must understand their mechanisms, their risks, their monitoring, and their antidotes with absolute certainty. In this environment, your expertise is not just valued; it is indispensable to preventing catastrophic harm to both mother and child.

33.6.2 Masterclass: High-Alert Medications in Labor & Delivery

While many medications are used in OB, the entire practice revolves around the masterful use of two powerhouse drugs: Oxytocin and Magnesium Sulfate. The order sets for these medications are some of the most rigid and detailed in the entire hospital for a reason.

Oxytocin (Pitocin): The Engine of Labor

• The “Why”: Oxytocin is a hormone that causes uterine contractions. It is used to induce labor (start it from scratch) or augment labor (strengthen or increase the frequency of existing contractions). It is also the first-line agent to prevent and treat postpartum hemorrhage by causing the uterus to contract firmly after delivery.
• The Risk: The primary danger of oxytocin is overstimulation of the uterus, a condition called uterine tachysystole (defined as >5 contractions in a 10-minute period). Excessively frequent or strong contractions do not allow the fetus adequate time to recover between them, which can compress the umbilical cord and lead to fetal hypoxemia, acidosis, and distress.
• The Protocolized Solution: Oxytocin is ALWAYS administered via an infusion pump using a standardized, premixed, low-concentration bag (e.g., 30 units in 500 mL NS). The protocol is one of “low and slow” titration. The order set will specify a low starting rate (e.g., 0.5-2 milliunits/minute) with instructions to increase the rate by 1-2 milliunits/minute every 30-60 minutes, titrating to a desired contraction pattern (e.g., one contraction every 2-3 minutes).
• Pharmacist’s Role: Your job is to ensure these safeguards are in place. You verify the standardized concentration. You confirm the order specifies the use of a smart pump with programmed guardrails. You must be able to recognize the difference between a high-dose postpartum hemorrhage regimen and a low-dose labor induction regimen.

Magnesium Sulfate: The Neuromuscular Dampener

• The “Why”: Magnesium sulfate has two distinct, critical uses in OB.
  1. For Preeclampsia/Eclampsia: It is used as a CNS depressant for seizure prophylaxis and treatment in patients with severe preeclampsia or eclampsia. It works by raising the seizure threshold in the brain.
  2. For Pre-term Labor (Tocolysis): At high doses, it relaxes smooth muscle, including the uterus, and can be used for the short-term (typically < 48 hours) to stop pre-term contractions. This is often done to buy time to administer corticosteroids for fetal lung development.
• The Risk: Magnesium has a very narrow therapeutic window. The dose required for seizure prevention is just below the dose that causes toxicity. Magnesium toxicity is life-threatening and progresses in a predictable pattern: loss of deep tendon reflexes, followed by respiratory depression, and finally cardiac arrest.
• The Protocolized Solution: The order set is extremely rigid. It will include a loading dose (typically 4-6 grams IV over 20-30 minutes) followed by a continuous maintenance infusion (typically 1-2 grams/hour). The protocol will mandate strict and frequent monitoring: respiratory rate, deep tendon reflexes, and urine output (as magnesium is renally cleared) must be assessed hourly.
• The Antidote: Every magnesium sulfate order set MUST include a STAT, immediately available order for the antidote: Calcium Gluconate 1 gram IV.
• Pharmacist’s Role: You are the final check on all calculations. You will verify the loading dose and the maintenance rate. You must confirm the patient’s renal function is adequate. Most importantly, you will ensure the mandatory monitoring parameters are ordered and that an order for the antidote is present and linked.

Part 2: The World of Pediatrics (Peds)

33.6.4 The “Why”: They Are Not Little Adults

If the guiding principle of OB is “two patients,” the guiding principle of pediatrics is far simpler, yet even more profound: everything is weight-based. Children are not miniature adults. Their physiology is in a constant state of flux, with dramatic changes in drug absorption, distribution, metabolism, and excretion (ADME) occurring from neonates to infants to toddlers to adolescents. Hepatic enzymes mature at different rates. Renal function evolves. Body composition (water vs. fat) shifts. Attempting to apply adult dosing principles to a child is not just incorrect; it is a recipe for disaster.

The single greatest risk in pediatric medication use is the tenfold dosing error. An accidentally misplaced decimal point can be the difference between a therapeutic dose and a lethal one. For this reason, pediatric order sets are ruthlessly standardized and packed with safety features. They are designed to force weight-based calculations, display dose-per-kg information, and link to standardized IV concentrations to minimize the need for complex bedside calculations. Your role as a pediatric pharmacist is to be the ultimate guardian of the decimal point. You must approach every single pediatric order with a healthy dose of paranoia, independently recalculating every dose from scratch, every single time. There are no shortcuts.

33.6.5 Masterclass: The Cornerstones of Pediatric Dosing Safety

The Pediatric Dose Verification Workflow

You must develop a rigid, systematic workflow for verifying every pediatric dose.

1. Find the Weight: Locate the patient’s current, measured weight in kg.
2. Find the Reference Dose: Use a trusted pediatric drug information resource (e.g., the Lexicomp Pediatric & Neonatal Dosage Handbook, Harriet Lane Handbook) to find the correct mg/kg/dose or mg/kg/day for the drug and indication.
3. Calculate the Dose: Perform the calculation independently. Formula: (Reference dose in mg/kg) x (Patient weight in kg) = Total dose in mg.
4. Perform a “Sanity Check”: Compare your calculated dose to the standard adult dose for the same medication. If your calculated pediatric dose is greater than the typical adult dose, this is a massive red flag. While there are a few rare exceptions, this almost always indicates an error in your calculation, the patient’s weight, or the provider’s order. You must stop and re-investigate.
5. Verify the Concentration & Volume: For oral liquids and IV medications, you must verify both the final **mg dose** and the corresponding **mL volume**. An order should always include both for clarity (e.g., “Acetaminophen 150 mg (10 mL) PO…”). This prevents nurses from confusing the dose with the volume and causing a major error with multi-dose bottles or different available concentrations.

33.6.6 Pediatric & Obstetric Order Sets in Practice

Let’s now apply these principles by deconstructing four specialty population order sets, two from obstetrics and two from pediatrics, to see how they are designed to manage risk and promote safety.

OB Example 1: The Labor Induction Order Set

Order Set Component	Example Orders from the Set	Clinical Logic & Pharmacist’s Critical Focus
Cervical Ripening	(If cervix is unfavorable) [ ] Misoprostol 25 mcg intravaginally every 4 hours. [ ] Dinoprostone (Cervidil) 10 mg vaginal insert x 1.	Logic: If the cervix isn’t ready for labor, prostaglandins are used to soften and dilate it before starting oxytocin. Pharmacist’s Focus: These are powerful uterotonics. Verify the tiny microgram dose of misoprostol. Ensure oxytocin is not started until a safe interval has passed after the last prostaglandin dose to avoid hyperstimulation.
Oxytocin Protocol	[X] Oxytocin 30 units in 500 mL NS. Administer via pump. [X] Start at 2 milliunits/min. [X] Increase by 1-2 milliunits/min every 30-60 min to achieve adequate contraction pattern. Max rate: 20 milliunits/min. [X] Continuous fetal and uterine monitoring.	Logic: This is the classic “low and slow” titration protocol designed to gently ramp up uterine activity while continuously monitoring for fetal tolerance. Pharmacist’s Focus: You must verify this is a standard, commercially-available premixed bag if possible. Confirm the starting rate and titration instructions match your institution’s approved protocol. Note the stark difference between this low milliunit/minute dosing and the high unit/hour dosing for postpartum hemorrhage.

OB Example 2: The Preeclampsia with Severe Features Order Set

Order Set Component	Example Orders from the Set	Clinical Logic & Pharmacist’s Critical Focus
Seizure Prophylaxis	[X] Magnesium Sulfate 4 gram IV loading dose over 20 min. [X] Followed by Magnesium Sulfate 2 grams/hr continuous IV infusion. [X] STAT Magnesium level 4-6 hours after loading dose. Goal: 4-7 mEq/L.	Logic: An aggressive loading dose is given to rapidly achieve a therapeutic level for seizure prevention, followed by a maintenance infusion. The lab goal ensures the level is therapeutic but not yet toxic. Pharmacist’s Focus: Re-calculate both the loading and maintenance dose. Verify the patient’s renal function (SCr) is adequate to clear magnesium. Question any maintenance rate higher than 2 g/hr without a clear justification.
Severe Hypertension Management	[X] Labetalol 20 mg IV push over 2 min for SBP ≥ 160 or DBP ≥ 110. [X] Hydralazine 5-10 mg IV push over 2 min for SBP ≥ 160 or DBP ≥ 110.	Logic: This provides the nurse with immediate tools to treat severe-range blood pressures, which pose a high risk of stroke in this population. Pharmacist’s Focus: These are potent IV antihypertensives. Ensure the parameters for administration are clear. Know the contraindications (e.g., labetalol in bradycardia).
Safety & Monitoring	[X] Hourly assessment of Respiratory Rate, DTRs, and Urine Output. [X] Seizure precautions. [X] Calcium Gluconate 1 gram IV, keep at bedside for STAT administration for magnesium toxicity.	Logic: This builds the safety net. The physical assessments are designed to catch the earliest signs of magnesium toxicity. The antidote is immediately available. Pharmacist’s Focus: You must verify that this entire cluster of safety orders is present. The magnesium order should never be verified without a corresponding order for the antidote and the required monitoring.

Pediatric Example 3: The Pediatric Community-Acquired Pneumonia (CAP) Admission Order Set

Order Set Component	Example Orders from the Set	Clinical Logic & Pharmacist’s Critical Focus
Patient Weight & Antibiotics	Patient Wt: 15 kg [ ] Ampicillin 50 mg/kg/dose (750 mg) IV every 6 hours. [ ] Ceftriaxone 50 mg/kg/dose (750 mg) IV every 24 hours.	Logic: First-line antibiotic choices for uncomplicated pediatric CAP, with dosing based on the “mg/kg” principle. Pharmacist’s Focus: Your entire focus is on the calculation. 1) Verify weight. 2) Look up reference dose (Ampicillin for CAP is 150-200 mg/kg/day divided q6h, so 37.5-50 mg/kg/dose. The order is correct). 3) Calculate: 50 mg/kg * 15 kg = 750 mg. 4) Sanity check: 750mg is less than a standard adult dose. The order appears correct. You will do this for every single drug.
Symptom Management	[X] Acetaminophen 15 mg/kg/dose PO every 4 hours PRN fever/pain. [X] Ibuprofen 10 mg/kg/dose PO every 6 hours PRN fever/pain.	Logic: Standard weight-based dosing for common antipyretics, allowing for alternation to improve symptom control. Pharmacist’s Focus: Re-calculate both doses. Calculate the max daily dose for both agents based on the child’s weight and ensure the orders do not exceed this. Specify the concentration of the oral liquid to be dispensed and the corresponding mL volume. (e.g., Acetaminophen 15 mg/kg * 15 kg = 225 mg. Using 160mg/5mL suspension, this is 7 mL).

Pediatric Example 4: The Neonatal Sepsis Rule-Out Order Set (NICU)

Order Set Component	Example Orders from the Set	Clinical Logic & Pharmacist’s Critical Focus
Antibiotic Therapy (The Classic Pair)	Gestational Age: 36 weeks. Postnatal Age: 2 days. Wt: 2.5 kg [X] Ampicillin 75 mg/kg/dose (188 mg) IV every 8 hours. [X] Gentamicin 5 mg/kg/dose (12.5 mg) IV every 36 hours.	Logic: This combination covers the most likely pathogens in early-onset neonatal sepsis (Group B Strep, Listeria, E. coli). The dosing interval for gentamicin is extended based on the neonate’s gestational and postnatal age to account for their immature renal function. Pharmacist’s Focus: Neonatal dosing is a sub-specialty. You will use a specialized neonatal reference. You will verify the extended interval for gentamicin is correct based on the baby’s age and weight (it is, for this example). Dosing errors here can cause permanent nephrotoxicity or ototoxicity. Precision is everything.
Therapeutic Drug Monitoring (TDM)	[X] Gentamicin random level 12 hours after first dose. [X] Pharmacy to manage all subsequent gentamicin dosing.	Logic: TDM is used to ensure the extended interval is appropriate, achieving a high peak for bacterial killing and a low trough to minimize toxicity. A random level is plugged into a nomogram (like the Hartford nomogram) to determine the appropriate new interval. Pharmacist’s Focus: This order explicitly delegates the management of gentamicin to the pharmacy. You will be responsible for obtaining the level, plotting it on the nomogram, and writing the order for the new dosing interval (e.g., “Continue gentamicin 12.5 mg IV every 48 hours”). This is a direct, high-impact clinical activity.