II. A peak blood level for orally administered theophylline (therapeutic range 8
ID: 305326 • Letter: I
Question
II. A peak blood level for orally administered theophylline (therapeutic range 8-20mg/L) measured at 8am is 5.0mg/L. The preceding trough level, drawn at 7am was 4.6mg/L.
a. What is the most likely explanation for these results?
b. If you were the patient’s physician and received these results, what would be the next step that you would most likely take?
III. A patient previously diagnosed with primary hypothyroidism and started on thyroxine replacement therapy is seen for follow-up testing 2wks later. The serum free T4 is now normal but the TSH is still elevated.
a. What is the most likely explanation for these results?
b. Should additional tests be run in order to determine if the replacement therapy is working? Why or why not?
IV. A patient with a provisional diagnosis of depression was sent to the laboratory for a routine workup. The CBC was unremarkable except for an elevated MCV. Results of a urinalysis were also unremarkable. The serum chemistry testing revealed a slightly increased AST, TBili and HDL with all other chemistry results within normal range. Based on the patient’s previous history, the physician suspected alcohol abuse. When questioned by the physician, the patient claimed that he no longer drank and was now dry. The physician, not really believing the patient’s claim, subsequently ordered an ethanol level and a GGT to be run on the blood that was drawn earlier. Testing revealed the patient’s GGT level to be 3x the upper limit and the ethanol was reported as none detected. Additional screening tests for infectious hepatitis were negative.
a. Are these results consistent with a patient who is consuming hazardous quantities of alcohol?
b. If this patient was indeed an alcoholic, what could be a possible explanation for his ethanol level being negative?
Explanation / Answer
II. A peak blood level for orally administered theophylline (therapeutic range 8-20mg/L) measured at 8am is 5.0mg/L. The preceding trough level, drawn at 7am was 4.6mg/L.
a. What is the most likely explanation for these results?
The peak should have been collected after 4-6 hours of administration of the oral drug and trough level always the lowest concentration of drug in blood stream.{Oral Dose: Measurement of peak concentrations is recommended, with sample drawn 4 hours following dose for slow release preparations, or 2 hours after dose for regular forms.https://www.nhrmc.org/healthcare-professionals/laboratory/specimen-collection/therapeutic-drugs-optimal-time-to-draw-samples}
b.If you were the patient’s physician and received these results, what would be the next step that you would most likely take?
Change the dose of theophylline and order re sample 48 hours after change in dose. Usually the steady state of drug normally takes three days from starting Theophylline.
III. A patient previously diagnosed with primary hypothyroidism and started on thyroxine replacement therapy is seen for follow-up testing 2wks later. The serum free T4 is now normal but the TSH is still elevated.
a. What is the most likely explanation for these results?
The dosage of thyroxine replacement therapy is inadequate, and other causes may be due to malabsorption, Poor compliance with medication,or any interaction with concomitant drugs.
b.Should additional tests be run in order to determine if the replacement therapy is working? Why or why not?
No need of additional tests.TSH can take up to 4 months to come to normal, even when starting on a full dose replacement regimen, due to thyrotroph hyperplasia. It is recommended that the TSH is measured 6–8 weeks after initiation of levothyroxine dose or change in dose .
IV. A patient with a provisional diagnosis of depression was sent to the laboratory for a routine workup. The CBC was unremarkable except for an elevated MCV. Results of a urinalysis were also unremarkable. The serum chemistry testing revealed a slightly increased AST, TBili and HDL with all other chemistry results within normal range. Based on the patient’s previous history, the physician suspected alcohol abuse. When questioned by the physician, the patient claimed that he no longer drank and was now dry. The physician, not really believing the patient’s claim, subsequently ordered an ethanol level and a GGT to be run on the blood that was drawn earlier. Testing revealed the patient’s GGT level to be 3x the upper limit and the ethanol was reported as none detected. Additional screening tests for infectious hepatitis were negative.
a. Are these results consistent with a patient who is consuming hazardous quantities of alcohol?
Yes , the patient has consumed alcohol,gamma -glutamyl transferase levels become elevated after 24 hours to 2 weeks of heavy alcohol consumption.
b. If this patient was indeed an alcoholic, what could be a possible explanation for his ethanol level being negative?
He may have consumed alcohol heavily prior day or two weeks before, so the ethanol was negative in blood. The concentration of ethanol in blood may be eliminated.