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One prescription after another

01 January 2008

Sixty-year-old Mrs F had just retired as a schoolteacher when she visited her GP, Dr L, complaining of tiredness. She also complained of weight gain over the previous few months, which particularly concerned her because her face “had gone all puffy”. She said it was making her feel quite depressed. Dr L requested some thyroid function tests. Based on the results, he diagnosed hypothyroidism, prescribed thyroxine and asked Mrs F to have another blood test a couple of months later.

The next time Dr L saw Mrs F she was feeling much better. Her latest blood test showed that she was euthyroid, and Dr L advised her to continue taking the same dose of thyroxine.

Over the next ten years or so, Mrs F regularly visited her GP practice to discuss her asthma and osteoarthritis. She requested thyroxine on repeat prescription, along with her other medications. Her prescriptions were signed by a variety of doctors from the practice. Although Mrs F usually chose to visit Dr L, if there was a more convenient appointment with another doctor she would take that instead. Mrs F didn’t ask any further questions about her thyroid condition and none of the doctors discussed changing her dose or monitoring her treatment.

Mrs F carried on taking her thyroxine tablets as instructed. When she was referred to an orthopaedic surgeon for assessment of her arthritic knee, the referral letter mentioned her regular use of thyroxine.

A decade after being diagnosed with hypothyroidism Mrs F had a CVA, which led to paralysis. Thyroid function tests showed that she had sub-clinical hyperthyroidism.

Expert opinion

The pharmacology expert suggested that Mrs F’s stroke could have been the result of arrythmias induced by excessive thyroxine therapy.

The GP expert was critical of the lack of monitoring. Regular blood tests would have indicated the need to reduce Mrs F’s dose. Without these, it was impossible to know how much thyroxine Mrs F needed to replace her deficit. Repeat prescriptions for thyroxine should, therefore, not have been signed without monitoring.

The case was settled for a substantial amount.

Learning points

Careful monitoring of repeat prescriptions is vital. They should only be given where there is adequate knowledge of the patient’s health. The doctor must be satisfied that the treatment serves the needs of the patient.

After an initial diagnosis and treatment of hypothyroidism, thyroid function should be tested every six to eight weeks to check the patient’s response to treatment. Once the patient is euthyroid, thyroid function tests should be carried out regularly. If levels are outside the normal range the thyroxine dose should be adjusted accordingly.

This case happened a few years ago. Since then, computerisation has made the management of repeat prescriptions more ordered. It is possible to implement a policy for managing repeat prescriptions, and then using the computer to monitor the prescriptions, and prompt any necessary remedial action. Used correctly, this can reduce the likelihood of a similar case occurring.

Monitoring patients with hypothyroidism is not straightforward, and it is not the role of Casebook to advise on the clinical management of patients. The learning point from this case is that, whatever system is in place, it needs to be robust and to be followed consistently.

Further reading

Monitoring Thyroxine Therapy, accessed online at www.gpnotebook.com

Toft AD, Beckett GJ, Thyroid Function Tests and Hypothyroidism, BMJ326(7384):295–6 (2003).

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