Pharmocology through the lifespan Flashcards
Which two groups prescribing is almost all off label?
pregnant women and breast feeding
In pregnancy which conditions need to be treated due to risk to mother and feats?
Epilepsy
Diabetes
Psychosis
Hypertension
How are systems affected during pregnancy?
reduced gut mobility
reduced lung function
increased fat deposit
increased skin circulatiom
What is teratogenicity?
The ability of a substance or agent to cause birth defects or developmental abnormalities in a developing fetus.
Give examples of a Tetragogen?
Nicotine: teratogenic and other effects (eg pre-term labour)
Alcohol ⇒ fetal alcohol syndrome
Named in 1970s, yet affects 3-8% of the population
Tetracycline ⇒ staining of teeth
What are the features of fetal Alcohol Syndrome?
Facial characteristics
Delayed development, especially behavioural and cognitive
No safe limit
How old is a Neonate (bnf)?
0-28 days
How old is a child (bnf)?
1 month to 17 years
How do children have altered pharmacokinetics?
Absorption,
Birth to 2/3 yrs gastric acid reduced & gastric mucosa immature.
E.G: penicillin – usually partly broken down by stomach acid, leads to absorption.
Immature gut will absorb whole proteins (why?)
Peristalsis reduced in first 6 months & gastric emptying slower.
Thinner skin & larger surface area relative to body weight – topical absorption higher.
Reduced bile production – fat soluble drugs absorbed slowly.
IM injections less well absorbed in neonates – low muscle mass & ↓ blood flow to muscles.
Cf. Vomiting & spitting out medication.
How is Childrens Metabolism different?
Enzymes for drug metabolism are undeveloped at birth.
Rapid metabolic rate ↑ age 1-9 yrs.
How is excretion of drugs different for children?
GFR & tubular secretion reduced
Renal clearance is reduced.
What other things to consider when prescribing for children?
Doses are calculated on an individual basis, often based on weight.
Most prescribing is “off-label”.
The formulation must be considered.
May involve the education of the parent/carer.
History obtained from parent/carer when prescribing for infant, older child gets more involved they will become; Gillick competency.
Try to use “old” drugs
Impressions made during a consultation with a child can “last a lifetime” – need to be mindful of maintaining a comfortable environment & good relationship.
What do we need to consider when prescribing for older people?
Some elderly patients are too compliant!
But is estimated to be approximately 50% on average
Can they read the label?
Can they open the pot?
Are they able to swallow it?
The regimen can be very complex
Liquids more prone to waste
Problems with sugar and dental health
What is Polypharmacy?
concurrent use of multiple medications by one individua
what do we need to consider with Polypharmacy?
May develop side effects from medication
may be mistaken as symptoms of a new disease.
Leads to the prescribing of more medication & risk of further side effects → “prescribing cascade”.
KEEP PRESCRIPTIONS AS SIMPLE AS POSSIBLE!
Which drugs should be used with caution?
Hypnotics
Diuretics
NSAIDs
Digoxin
Psychotropic drugs
Antiparkinsonian drugs
Antihypertensives
Pharmacokinetics- what absorption issues in the older person?
Reduced HCl produced by parietal cells in the stomach → higher pH → reduced uptake of acidic drugs.
Delayed gastric emptying
Slowed peristalsis.
Cf. Reduced GI blood flow delaying absorption.
Pharmacokinetics- what distribution issues in the older person?
Body composition
Body water reduced which affects the Volume distribution of some drugs
Plasma proteins
Reduced blood flow
Pharmacokinetics- what metabolism issues in the older person?
> 70yrs – liver blood flow reduced to 40-45%
Liver blood flow is also reduced by other comorbidities such as LV dysfunction or CHF.
First pass effect reduced.
Pharmacokinetics- what excretion issues in the older person?
Kidney function declines
Age 80yrs eGFR approx. half of age 25yrs
Name someting you can do to increase safety?
If in doubt increase the dosing interval
How is kidney function affected with age?
Knowledge of the patients’ renal function is essential to determine whether the drug should be given or if it should be given at a lower dose.
Routine method of estimating renal function is through eGFR.
eGFR calculated using age, sex, ethnic origin, and creatinine. Calculators can be found on the internet.
Renal function reduces with age, should always assume that there will be at least mild renal impairment in the older patient.
