Your questions to the PBAC

Readers are invited to write in with their questions about decisions of the Pharmaceutical Benefits Advisory Committee (PBAC). Australian Prescriber publishes selected questions from readers, together with answers from the PBAC. Questions may address issues such as regulatory decisions, pharmaceutical benefits listings and withdrawals.

This exclusive arrangement helps Australian Prescriber readers understand how the contents of the Pharmaceutical Benefits Scheme (PBS, see www.pbs.gov.au) are determined.

Letters and responses are reviewed by the Editorial Executive Committee and may be edited before publication. It may not be possible to reply to all individual questions.

Your questions to the PBAC

Changes to the Doctor's Bag Supplies

Sir, - Could the PBAC consider including adenosine and activated charcoal in the Emergency Drug (Doctor's Bag) Supplies and deleting verapamil?

Kevin O'Dempsey
General Practitioner
Kallangur, Qld

PBAC response:
The only form of activated charcoal listed on the Schedule of Pharmaceutical Benefits at the moment is the 300 mg tablet which is not appropriate for the management of poisoning. As noted in an Australian Prescriber article ('Activated charcoal: a spoonful of sugar' Aust Prescr 1997;20:14-6), activated charcoal has become the preferred treatment for most poisonings, with gastric lavage and ipecacuanha now being rarely used. Activated charcoal used for the management of poisonings is supplied as a slurry in 50 g bags, the slurry being made to 300 mL with either water or sorbitol. As Dr O'Dempsey implies, there is a place for the pre-hospital use of activated charcoal (the sooner the better) and little potential risk. The PBAC has not received an application for listing of activated charcoal in this form, but would certainly carefully consider such an application against its usual criteria.

Adenosine is used for similar indications to verapamil injection. However, the approved product information for adenosine states 'Adenocor should be used only in hospitals with monitoring and cardiorespiratory resuscitation equipment available for immediate use. Adenocor should only be used when facilities exist for cardiac monitoring'. Given these requirements, adenosine would not be suitable for listing as a Doctor's Bag supply. While similar considerations may clinically apply to verapamil injection, they are not included in the product information and there is much longer experience with verapamil than there is with adenosine.

Digoxin in the Doctor's Bag
Sir, - Having recently discovered that parenteral digoxin (ampoules) has been withdrawn from the Emergency Drug (Doctor's Bag) Supplies, I would earnestly request that you ask the appropriate authorities to rectify this grave omission.

In support of this request, I could furnish you with dozens (if not scores) of patients with acute CCF (pulmonary oedema, etc.) who have been resuscitated with the standard therapy of digoxin and diuretic.

D.M. Walsh
General Practitioner
The Entrance, N.S.W.

PBAC response:
The onset of effect of digoxin, even if given intravenously, is determined by the rate of distribution to the site of action. Even after an intravenous dose, it takes some 3-6 hours to achieve the full effect from the dose. This is the reason that digoxin plasma concentration measurements taken within 6 hours of the dose are not valid. It is also the reason why digoxin loading, whether intravenous or oral, is carried out usually over 24 hours with 3 divided loading doses. It is therefore not appropriate to use intravenous digoxin unless it is because the patient is unable to take or tolerate the oral formulation (e.g. if the patient is vomiting). The PBAC further noted that in situations where rapid digitalisation is required, hospital treatment with the availability of ancillary services would usually be appropriate.

The standard treatment for the initial therapy of acute pulmonary oedema involves frusemide plus glyceryl trinitrate with or without morphine (see Cardiovascular Guidelines, Therapeutic Guidelines Limited). Digoxin is only recommended if the patient is in atrial fibrillation and this is contributing to the cardiac failure. The Guidelines then recommend digoxin loading as 3 separated doses either intravenously or orally over 24 hours. The PBAC considered that continued listing of digoxin as a Doctor's Bag item was not appropriate.

Sumatriptan 50 mg tablet
Sir, - As of 1 May 1997, sumatriptan has a PBS listing. To my surprise and amazement, the listing is for two 50 mg tablets and the dispensed price at the least will be $15.29. I am informed that the cost of each tablet is $5.20, leaving a dispensing fee of almost $5.00. It seems quite extraordinary to be able to prescribe only two tablets at a time, for a condition which is chronic and likely to require repeated medication over a long period of time. The Government may have persuaded the drug company to reduce their cost of the tablets, but it seems to me that the pharmacists are now going to reap a considerable reward with the dispensing fee each time a patient on sumatriptan has a headache and therefore needs to repeat their prescription. Could you explain the logic behind the failure to be able to prescribe many more tablets with each prescription.

David Sharpe
Neurologist
Randwick, N.S.W.

PBAC response:
The general policy for the quantities of drugs listed under the PBS is to provide a maximum quantity representing approximately one month's supply at average maintenance dosage levels for drugs used on a chronic basis, or sufficient to treat an episode for drugs used for acute conditions.

Published data1,2 provided to the PBAC when considering the listing of sumatriptan indicated that the average frequency of migraine attacks was about one per month. Also, data from usage under the Special Access Scheme indicated that the average quantity of tablets used was 1.5 per attack.

The listing with a maximum quantity of two was thus chosen as most suitable.

Provision for increased quantities was excluded to prevent inappropriate use and overuse where the cost-effectiveness of therapy could not be supported. The published data overall indicate that, while sumatriptan is better than alternative treatments such as ergotamine or aspirin plus metoclopramide, this superiority is not marked e.g. headache relief at two hours for the first attack is 56% with sumatriptan and 45% with aspirin plus metoclopramide.3 One study found no difference between sumatriptan and aspirin and metoclopramide.4

Placebo response rates in the trials were of the order of 24%4 to 30%.5

Extensive use of this expensive drug in situations where cheaper alternatives are likely to be effective was considered unacceptable in terms of both cost-effectiveness and overall cost to the taxpayer.



References

  1. Sumatriptan, serotonin, migraine, and money [editorial]. Lancet 1992;339:151-2.
  2. Stewart WF, Lipton RB, Celentano DD, Reed ML. Prevalence of migraine headache in the United States. Relation to age, income, race, and other sociodemographic factors. JAMA 1992;267:64-9.
  3. The Oral Sumatriptan and Aspirin plus Metoclopramide Comparative Study Group. A study to compare oral sumatriptan with oral aspirin plus oral metoclopramide in the acute treatment of migraine. Eur Neurol 1992;32:177-84.
  4. Tfelt-Hansen P, Henry P, Mulder LJ, Scheldewaert RG, Schoenen J, Chazot G. The effectiveness of combined oral lysine acetylsalicylate and metoclopramide compared with oral sumatriptan for migraine. Lancet 1995;346:923-6.
  5. The Oral Sumatriptan International Multiple-Dose Study Group. Evaluation of a multiple-dose regimen of oral sumatriptan for the acute treatment of migraine. Eur Neurol 1991;31:306-13.