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Interim decisions and invitation for further comment on substances referred to the March 2019 ACMS/ACCS meetings

Scheduling of chemicals and poisons

6 June 2019

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1.3. Interim decision in relation to isosorbide dinitrate

1 Interim decisions on proposed amendments referred to the Advisory Committee on Medicines Scheduling (ACMS #26, March 2019)

1.3. Interim decision in relation to isosorbide dinitrate

Interim decision:

For the reasons set out below, a delegate of the Secretary has, in relation to the proposed amendment, made an interim decision under regulation 42ZCZN not to amend the current Poisons Standard in relation to isosorbide dinitrate.

Reasons for the interim decision (including findings on material questions of fact):

I agree with the committee's finding that the matters under section 52E of the Therapeutic Goods Act 1989 are not relevant to the decision regarding the inclusion of isosorbide dinitrate in Appendix H.

In my view, the relevant part of the SPF, 2018 is the section on the considerations for amending Appendix H, in particular, the Guidelines for advertisements for medicines containing Schedule 3 substances.

Reasons for interim decision:

I have made the decision that isosorbide dinitrate should not be included in Appendix H of the Poisons Standard for the reasons set out below. In making my decision I have considered that there is potential for inappropriate use of isosorbide dinitrate which could be exacerbated by advertising.

Unlike glyceryl trinitrate, isosorbide dinitrate is not a first line treatment for angina. Dependence and tolerance can develop quickly with sustained use of isosorbide dinitrate and during sustained therapy, cross tolerance to other nitrate treatments may occur reducing their efficacy and, in terminating treatment, the dosage and frequency of administration must be gradually reduced to prevent potential withdrawal reactions such as increased frequency of angina attacks.

The advertising of isosorbide dinitrate may lead to erroneous requests for the substance from both patients with an angina diagnosis and patients without a proper diagnosis. Furthermore, there is potential for advertising to exacerbate this confusion by consumers with regards to appropriate treatment regimens for their condition. In my view, the risk that some patients may be supplied with isosorbide dinitrate incorrectly as treatment for angina at a pharmacy outweighs the benefits of a greater awareness of over-the counter access for patients through advertising.

In addition, I consider that there are additional risks associated with the dosage form of isosorbide dinitrate that could impact on its safe use. Both the 5mg sublingual tablet and the 10mg oral tablet are in Schedule 3; it is my view that there is a reasonable possibility that advertising may exacerbate confusion among consumers about which form/strength is taken orally and which is used sublingually.

Having considered the evidence, I have, in making my decision, relied on the evidence that isosorbide dinitrate is not a first line treatment for angina and it is not intended to treat acute angina episodes. The advertising of isosorbide dinitrate for angina treatment may result in some patients erroneously requesting this over other recommended treatment(s). Patients with angina should be under the treatment of a medical practitioner and will therefore be aware of the availability of isosorbide dinitrate treatment regimens if relevant to their condition.

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