Monitoring of tobramycin levels in patients with cystic fibrosis by finger-prick sampling

To the Editors: Chronic pulmonary infection is the major cause of morbidity and premature mortality in patients with cystic fibrosis (CF). The major pathogen for patients with CF is Pseudomonas aeruginosa . Tobramycin, an aminoglycoside antibiotic, is widely used against Gram-negative bacterial infections and is particularly useful for the treatment of P. aeruginosa in patients with CF [1]. Intravenous tobramycin has a narrow therapeutic range and monitoring of the drug is required to reduce serious side-effects, such as nephrotoxicity and ototoxicity [2]. Dosage alterations based on the results of drug monitoring can improve efficacy and minimise toxicity. Monitoring currently requires venesection and patients may find finger-prick samples less painful and more acceptable. Finger-prick blood sampling is routinely performed by patients with diabetes mellitus, is an easy technique to teach and uses inexpensive equipment which is widely available. We have previously shown that finger-prick sampling is a safe and accurate alternative to venous sampling for measurement of tacrolimus levels in children with kidney transplants [3]. Anecdotal experience in children's hospitals suggest that children generally prefer finger-prick sampling to venous sampling, even where topical anaesthetic agents are used for the latter. Studies in adult patients, including solid organ transplant recipients [4] and those receiving anticoagulant therapy [5], have shown a preference for finger-prick over venous blood sampling. We performed a prospective study to compare the results of tobramycin levels in adult patients with CF measured by finger-prick samples with those from …