Monitoring

Question 1

What info needs to be given to a pt starting methotrexate?

Answer 1

Sore throat, fever or unexplained bruising may result from methotrexate-induced bone marrow suppression causing neutropenia or decreased platelet production. Other serious potential adverse effects include cirrhosis and pulmonary toxicity.
FBC, LFT, U+E at baseline, every 1-2 weeks until dosage is stabilised + every 2-3 months thereafter.
Once weekly
Folic acid taken on a different day once weekly
NSAIDs interact so avoid self medication

Question 2

What info is needed when starting a pt on digoxin?

Answer 2

Measure levels 8-10days after initiating treatment or changing dose (esp in elderly)
Therapeutic range of 1.0-2.0 nmol/L. Measurements should be made 6 hours post-dose
Dose reduced in renal impairment (monitor renal function)

Question 3

How do you monitor levothyroxine treatment in someone with hypothyroidism?

Answer 3

TSH measured in 2-3months (allows for resolution of pituitary hyperplasia)
Target concentration 0.4-2.5 mU/L (0.4-5.0) Dose adjusted by 12.5-25 micrograms daily to achieve this.
Symptomatic relief is the ultimate aim of thyroid replacement therapy and fatigue, drowsiness and subtle cognitive impairment are sensitive markers of suboptimal treatment

Question 4

What drugs have their concentrations monitored?

Answer 4

Gentamicin + digoxin (to avoid toxicity, especially in patients with renal failure)
Phenytoin and IV theophylline/aminophylline (to achieve therapeutic concentrations whilst avoiding toxicity)
Vancomycin (to avoid renal toxicity and ototoxicity)

Question 5

When is a steady state plasma level usually achieved?

Answer 5

After 4-5 drug half lives

Question 6

What happens to TSH levels if too much or too little levothyroxine is given?

Answer 6

Too much levothyroxine: complete suppression of TSH

Too little: TSH rises