Therapeutic Drug Monitoring

Responsibilities of the Healthcare Professional

  1. Request - Doctor to complete a blood sample form to alert phlebotomist/nurse/doctor to take bloods from patient. The kardex should be annotated with a box to indicate when level is to be taken. If doses are to be withheld pending results, this should be clearly documented on the kardex. If the phlebotomist is not on the ward at the time the sample is to be taken, the responsibility lies with the doctor to ensure the sample is taken at the correct time.

  2. Sampling - Phlebotomist/Doctor/Nurse to take blood sample at appropriate time as per kardex and record sampling time on form. Yellow topped bottles are required for the majority of drugs. The sample should be sent to biochemistry before 4pm.

  3. Administration of drug - Nurse to administer drug at the correct time on a regular basis. Nurse to ensure patient is weighed and the weight is documented on the kardex. Nurse to give the next dose as prescribed unless instructed otherwise. If drug not given at prescribed time, the nurse should document time given clearly on drug kardex.

  4. Analysis - The Duty Biochemist is available to give advice on sampling and analysis, Ext 2136, Monday - Friday, 9.00-17.30. If for any reason you need help to convert between units, please contact the Duty Biochemist.

  5. Interpretation of results - Pharmacist to advise on appropriate time to sample and record in medical notes along with recommended dose range for the drug. Pharmacist to advise doctor on individual patient factors such as renal function, interacting medication, age and weight. Doctor to consider interacting drugs and patient condition when interpreting levels and to refer to ward pharmacist/medicines information (Tel 3331) for advice. Doctor must make clear on drug kardex if next dose(s) not to be given otherwise nurse is expected to administer.

For antibiotic and antifungal monitoring, please see the antibiotic monitoring section. Antibiotic interpretation should be directed to a consultant microbiologist.

If tests are urgently required then please contact the Duty Biochemist via switch.

Wherever possible, all requesting of Biochemistry tests should be done electronically using Sunquest ICE (further details here).

Test

Sample Type

Test Frequency

Target Range

Carbamazepine

Serum, pre-dose trough

Daily

4-10 mgl/l

concern level: 25 mgl/l

Cyclosporin

EDTA

Daily

Variable

Digoxin

Serum, >6 hrs post-dose

Daily

1.0-2.0 mgl/l

concern level: 3.0 mgl/l

FK506 (Tacrolimus)

EDTA, pre-dose

Daily (Mon-Fri)

5-12 µg/l

Lamotrigine

Serum, pre-dose trough

 Weekly (Thurs)

3-15 mg/l

concern level: 30 mg/l

Lithium

Serum, pre-dose or >12 hrs post dose

Daily

0.5 - 0.8 mmol/l

Phenobarbital

Serum, pre-dose or random

Monday & Thursday

10-30 mg/L

concern level: 75 mg/l

Phenytoin

Serum

Daily

8-15 mg/L

concern level: 20 mg/l

Sirolimus

EDTA

Twice weekly

Variable

Theophylline

Serum, pre-dose

Daily

10-20 mg/l adult

5 -10 mg/l neonatal apnoea (patients vary)

Valproate

Serum, pre-dose

Friday

50-100 mg/l

Trust Medicines Information Service: 291 3331