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The Pharmaceutical Journal
Vol 270 No 7238 p295
1 March 2003

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Drug & Therapeutics Bulletin (more)

Pharmacists must help to manage the use of amiodarone in primary care

Community pharmacists must be alert to the possible unwanted effects of amiodarone, according to a consultant cardiothoracic pharmacist.

Mojgan Sani, consultant pharmacist, cardiothoracic centre, Guy's and St Thomas' Hospital Trust, spoke to The Journal in the light of a review of amiodarone safety published in the Drug & Therapeutics Bulletin last week (2003;41:9). The review outlines the drug's potential to cause unwanted effects, some of which can be fatal.

The bulletin emphasises that, though amiodarone is usually initiated and monitored under hospital supervision, responsibility for maintenance therapy often falls to the general practitioner. In England, in 2001, around one million scripts for this drug were dispensed in primary care. "Most serious toxicity is seen with long-term use and may therefore present first to GPs. Prompt recognition and action usually reverses toxicity, although due to the drug's long half life, reversal may be slow," the DTB says.

Mrs Sani points out that first presentation may actually be to the pharmacist. She notes that awareness of the adverse effects of amiodarone is a good example of how community pharmacists can effectively be involved in medicines management and review. "Polypharmacy may be particularly important in this respect," Mrs Sani says. She adds that a multidisciplinary approach is needed to ensure that patients taking amiodarone who experience unwanted effects are quickly referred back to the GP and, if necessary, their cardiologist.

The bulletin reminds doctors and pharmacists that amiodarone is licensed for the treatment of severe cardiac rhythm disorders where other treatments have failed or cannot be used. It has several dose-dependent or idiosyncratic adverse effects (see Table).

Table: Dose-dependent or idiosyncratic adverse effects of amiodarone

Unwanted effect	Signs
Pulmonary toxicity	Cough, progressive shortness of breath
Thyroid dysfunction	Hyper or hypothyroidism may occur, may appear as worsening of existing cardiac disorder, hyperthyroidism may appear after treatment is discontinued — monitoring required
Liver damage	Elevated liver transaminases — monitoring required
Cardiac toxicity	Cardiac symptoms may develop or worsen — ECG required
Visual disturbances	Haloes or blurred vision — may warrant discontinuation
Neurological	Tremor, ataxia, peripheral neuropathy associated with high loading doses, usually improve on maintenance
Skin toxicity	Photosensitivity or blue/grey skin discoloration

The DTB says that amiodarone's unwanted effects seem to occur less frequently with low-dose maintenance therapy (100-200mg) than with older, higher-dose regimens (above 400mg daily) but there are no direct comparisons. Patients should have careful clinical assessment and monitoring before starting therapy. Thereafter, measurements of thyroid function, liver enzymes and possibly potassium concentration should be monitored every six months.

Professor Joe Collier, editor of the DTB, says: "Supervision of patients in the community needs the GP to be alert and informed."

He cautions: "The decision to withdraw amiodarone or modify dosage should only be made in consultation with a specialist."