Class notes
4th Year Biomedical Sciences notes - Anaemia - Therapeutic Drug Discovery
- Course
- Institution
Notes from two lectures from Dr. Moffat and Dr. Walsh from the course of Advanced Blood sciences
[Show more]
Seller
Follow
krzysztoflipiec
Content preview
ADVANCED BLOOD SCIENCEDR. WALSH
THERAPEUTIC DRUG MONITRING
Definition:
Use of drug measurements in body fluids as an aid to management of patients receiving drug
therapy for the cure, alleviation or prevention of disease, whilst minimising the risk of
toxicity.
The primary determinant of clinical response is concentration achieved at site of action.
There are certain criteria for TDM:
1) Narrow therapeutic range (window)
2) Overdose symptoms are similar to disease being treated
3) Drug produces abnormalities in hepatic/renal clearance
a. Because liver and kidney are main sites for clearance and metabolism of
drugs.
4) Drug absorption varies with dose
TDM due to clinical problems:
1) Establishing/changing dose regime
a. The patient may require different drug, different dose and it is important to
monitor those changes
2) Failure to achieve therapeutic control
3) Loss of control in previously stabilised patient
4) Check for toxicity
DOSAGE:
Suboptimal (subtherapeutic) – low [plasma]
o Just below the therapeutic window
Above therapeutic threshold, drug clinically effective
Above toxic threshold, adverse effects
Therapeutic window, [plasma] between therapeutic & toxic thresholds
,Y-axis = plasma concentration It takes time for some drugs to establish the
correct plasma levels – antidepressants,
X-axis = time antibiotics
After several similar doses – steady state (usually 4-5 half-lives)
It oscillates between peaks and troughs
Stable relationship between dose and effect is the key purpose of TDM
SAMPLING
, Take measurements immediately pre-dose (trough concentration) – as they are most
reproducible
Peaks are more relevant to diagnosis of toxicity
Should always take note of time of sampling and last date.
INTERPRETATION
If the concentration is lower than expected – the most likely cause could be non-
compliance (patient not sticking to the instructions)
If the concentration is higher than expected – the possible causes are hepatic or renal
failures – they cant metabolise and transport waste properly. Also, the change in other
drug therapy could cause increase in plasma concentrations of a drug.
It is important to remember that therapeutic range is just a rough guide and not
decisive test.
INTER-INDIVIDUAL VARIATION
This is another important aspect of drug monitoring. Each individual will react differently to
the drug and his body will deal differently with the drug. It is important to take notice of that
, when prescribing the medication/therapy. There are two main distinctions within the
variation:
1) Pharmacokinetics – what body does to the drug
2) Pharmacodynamics – what drugs do to body
Non-compliance is a very common source of serious complications associated with drug
therapy monitoring. Essentially the patient is responsible for taking the prescribed drug. This
is especially important in remission or prophylactic (epilepsy).
Non-compliance is also easily detected – by blood tests (low or non-present plasma levels of
the drug)
Variable compliance is more difficult to detect and deal with – this happens when patient
takes the drug, then stops for few days, then take double dosage etc.
PHARMACOKINETIC FACTORS (BIOAVAILABILITY)
This refers to amount of drug reaching the circulation
There is a considerable variation in % absorbed – this is known as bioavailability (F)
dose reaching circulation
F=
dose administered
This varies between drugs, individuals and dosage forms (the pill, powder, IV
injection all will react differently)
Bioavailability depends on number of factors including:
1) Dissolution properties
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller krzysztoflipiec. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.18. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
67474 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now