Clinical Skills

What is the neonatal period?

First 28 days of life - the period where they are particularly susceptible to toxicity

Who fall under the category of paediatric patients?

What is dosing in paediatrics determines by?

Mainly:

• Dosing by total body weight (TBW)

• Dosing by specific age ranges

However, can also be based on:

• Dosing by body surface area (in m²)

• Corrected gestational age for preterm neonates

• Dosing by Ideal Body Weight (IBW)

What is corrected gestational age?

Corrected gestational age is the neonate's total age expressed in weeks from the start of the mother's last menstrual period —> some drugs may have dosed based on the corrected gestational age

e.g. 3-week old baby born at 27 weeks gestation is treated as having a corrected gestational age of 30 weeks

How do you calculate a child’s BSA?

1)Calculate weight in kilograms: 37 pounds ÷ 2.2 =  16.8 kg

2)Calculate height in centimeters: We know our patient is 97cm tall

3)Multiply height by weight and divide by 3600 (97 cm x 16.8 kg) ÷ 3600 = 0.45

4)Take the square root of 0.45 = 0.67 m²

Define Infant apnoea

"an unexplained episode of cessation of breathing for 20 seconds or longer”, generally associated with bradycardia, cyanosis, pallor, and/or marked hypotonia

How do we dose children who may be considered “obese”?

Using “Ideal Body Weight” due to the risk of toxicity if the BSA or the TBW is used

How can different drugs affect pregnancy?

• During the first trimester drugs can produce congenital malformations (teratogenesis), and the period of greatest risk is from the third to the eleventh week of pregnancy

• During the second and third trimesters drugs can affect the growth or functional development of the foetus, or they can have toxic effects on foetal tissues

Stages of Pregnancy

First 17 days - pre-embryonic phase

• Exposure to a drug during this time will either result in survival of the intact embryo or death.

• This is sometimes known as the “all or nothing principle”

18 to 55 days – embryonic phase

• The embryo will be most vulnerable to teratogens during this time. Drugs can produce congenital malformations (teratogenesis).

56 days until birth – foetal period

• Organs such as cerebral cortex and renal glomeruli continue to develop. Drugs can affect the growth or functional development of the foetus, or they can have toxic effects on foetal tissues e.g. a functional abnormality such as deafness may occur during this period.

PK Changes in pregnancy

Absorption:

• meds may not stay down long enough to be absorbed if hyperemesis

• Timing may change or given alongside an anti-emetic

Distribution

• Plasma volume increases progressively through normal pregnancy

• Total body water increases by 8 litres along with decreased plasma albumin concentration so free levels of drug may rise.

• Regional blood flow changes e.g. more blood flow to the uterus and less to the muscle

Metabolism

• Progesterone can also affect hepatic enzyme changes e.g. reduced N-demethylation activity

Elimination

• Higher cardiac output (increased by 20% by 8 weeks of pregnancy) and GFR and renal plasma flow also increased – has an affect on renally excreted drugs

What is Childbearing Age?

15 – 55 years old so should consider giving “pregnancy” advice and warnings to these patients especially if on medications which are dangerous during pregnancy e.g. valporate 3-4/10 children are born with a defect/developmental problems

References for medications use in pregnancy

• BNF

• NICE

• Specialist pharmacy Service

• Medicines Complete

General monitoring in pregnancy patients

• At least two ultrasounds (8-14 weeks and another at 18-21 weeks)

• Blood tests

• BP

• Urine tests

• Monitoring for gestational diabetes

Why is breastfeeding beneficial?

the immunological and nutritional value of breast milk to the infant is greater than that of formula feeds

What are the worries with breastfeeding?

• The amount of drug or active metabolite of the drug delivered to the infant (dependent on the pharmacokinetic characteristics of the drug in the mother)

• The efficiency of absorption, distribution, and elimination of the drug by the infant (infant pharmacokinetics)

• The nature of the effect of the drug on the infant (pharmacodynamic properties of the drug in the infant).

Which PK factors are advantageous in breastfeeding?

Absorption:

• Poor oral availability is good because less is transferred into the milk

Distribution

• High Vd = lower plasma conc = lower conc in milk transferred

• Plasma binding: less binding = more in milk

Metabolism

• First pass

Elimination

• Very little drug is transferred/eliminated into human milk

What special resources are used for drugs in breastfeeding?

• Lactmed

• UKDILAS

• EMC

• NIH

• The Breastfeeding Network

• Drugs in Breastmilk

• Breastfeeding helpline

What is the monitoring in breastfeeding patients?

• Is the baby thriving? Meeting expected milestones?

• Plenty of wet and dirty nappies?

• Is the milk supply ok?

• Is the baby showing any signs of drowsiness or other changes in behaviour?

Resources for Pregnancy

• British National Formulary (BNF) and BNF for Children (BNFc)

• Summary of Product Characteristics (SPC)

• UK National Teratology Information Service (UKTIS)

• Specialist Pharmacy Service