Drug laboratory interactions Dr Marriam Zaka Lecturer Institute

Drug laboratory interactions. Dr Marriam Zaka Lecturer Institute of Phramacy, Faculty of Pharmaceutical and Allied Health Sciences LCWU, Lahore.

Drug lab interactions.

Drug lab interactions. Drug lab test interactions are those interactions which effect the results of normal lab reports due to presence of one or more drug which can be a cause of interference. False positive and false negative results can be the outcome.

Drug lab interactions. Lab tests, pt medical history and physical examination are vital components for a diagnosis, screening, and management of a disease. Lab tests can be influenced in sensitivity and specificity by drugs consumed by patient. Whenever a drug lab interaction is observed in a clinical setting it should be discussed in medical community to avoid possible error in diagnosis.

Types. 2 major types are: Pharmacological or in vivo interference. Methodological or in vitro interference.

Pharmacological interference. This is related to direct action of drug or its metabolites inside the body other than depending upon method of testing. This type is most frequent. Example: Thiazide diuretics elevate the sugar level from weeks to years and can interfere in glycaemic tests of diabetic patients.

Methodological interference. Is the interference with method of testing. An example is of interference with color as most of lab tests in chemical pathology have a colorimetric component which can be interfered by foreign chromogens. Creatinine measurement and the color changes of urine samples (ferrous salts turn urine sample black , Rifampicin turns urine orangish red. )is an example.

Common lab tests. Urea, creatinine and electrolytes. Glucose( fasting & random). CBCs. LFTs. Urine chemistry. Others.

Some examples of drug lab interactions. ESR: is elevated by oral contraceptives, vitamin A, and by methyldopa. Is decreased by corticosteroids , methotrexate, and by NSAIDS. Pregnancy test (Gonadotrophins): False positive by phenothiazines and methadone.

Some examples of drug lab interactions. Bilirubin : Increased by acetaminophen , barbiturates, erythromycin, diuretics( loop & thiazides) Decreased by corticosteroids, vitamin C, phenytoin, levodopa.

Some examples of drug lab interactions. Cholesterol : Increased by b- blockers, aspirin, anabolic steroids, diuretics, oral contraceptives. Decreased by a- blockers, ACE inhibitors, Ca channel blockers.

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