A review of PBS dispensing data for teratogenic drugs to women of reproductive age has revealed ‘unacceptably low’ rates of concurrent hormonal birth control.

The new paper by Flinders University and South Australian Health and Medical Research Institute (SAHMRI) researchers investigated prescribing trends for Category X drugs  – such as misoprostol – that have such a high risk of causing permanent damage to the fetus that they should not be used in pregnancy or when there is a possibility of pregnancy.

It found that fewer than a quarter of women taking a Category X drug were using any form of hormonal contraception. Of these women, just 13.2% were on the more effective long-acting reversible contraception (LARC) – recommended in guidelines as best practice contraception for women of reproductive age taking Category X drugs, with its failure rate below 1%.

In Australia some medications with teratogenic risk are classified as category D (‘Drugs which have caused, are suspected to have caused or may be expected to cause, an increased incidence of human fetal malformations or irreversible damage’).

The findings, based on a 10% sample of PBS data, showed that dispensing of Category X medicines to women aged 15-49 years doubled over an eight-year period from 4.63 per 1000 women in 2013 to 8.70 per 1000 in 2021.

Investigators, led by clinical pharmacist Associate Professor Luke Grzeskowiak, say the largest increase was due to the dispensing of isotretinoin for the treatment of acne. The drug causes ‘major untreatable and lifelong birth defects in as many as 35% of exposed babies’, investigators add arguing that the suboptimal rates of concurrent contraception dispensing should raise questions about the effectiveness of measures for reducing the potential harms of Category X medication use during pregnancy.

Isotretinoin prescribing in Australia is largely restricted to dermatologists but the study findings have prompted some experts, both here and overseas, to suggest that it is time to reconsider broadening prescribing rights in Australia to GPs – as is the practice in countries like New Zealand and the Netherlands.

It’s not the first time the drug’s restricted prescribing status has been called into question. A 2014 submission by the Royal Australian College of General Practitioners called for prescribing responsibilities to be expanded to general practitioners, who are ‘well placed to provide access to a range of contraceptive methods, as many are trained in LARC insertion or can better facilitate access to LARC insertion’.

Writing in an accompanying editorial, Dr Sarah Donald from the Department of Preventive and Social Medicine, Otago University, noted that contraception prescribing and LARC insertion are outside specialists’ usual scope of practice, and therefore women must attend a different health provider for contraception care, “which they might not do”.

She argues that specific action to increase effective contraception by women using teratogenic medications should be ‘a priority’.

While a specially established expert roundtable identified several barriers to LARC use in Australia, including insufficient training of and support for primary care medical practitioners as well as access and financial barriers, Dr Donaldson pointed to a Melbourne study, which found that LARC uptake tended to be higher among women who attended general practices where a combination of training in effectiveness-based contraception counselling and rapid referral to a LARC insertion clinic were provided.

While acknowledging that it’s ‘likely’ the investigators’ data in the current study may underestimate contraception use among the cohort because some of the women appearing to have no contraception will be using the intrauterine copper device (IUD) or pills that are not subsidised on the PBS, Dr Donald maintained that contraception among women using teratogenic medications is ‘probably unacceptably low’.

Across the cohort, the proportion of women with LARC overlap was smallest for those dispensed dermatological agents (1806 of 14 331 women, 12.6%). Even further, data revealed that both LARC overlap and any hormonal contraception overlap were less likely for those aged 15–19 years than for women aged 25–29 years.

The study is one of several this year to expose the gaps between Category X drugs and the coordination of effective contraception prescribing.

A study published in May by Nepean Hospital Maternal Fetal Medicine specialist Dr Laura Gerhardy and colleagues also used PBS dispensing claims from a 10% sample of 15-44-year-old Australian women between 2013 – 2021. That study described rates in dispensing claims for PBS-listed retinoids and contraceptives and reported that oral retinoid dispensing doubled over the study period, from 14 dispensings per 1000 population in 2013 to 28 per 1000 in 2021. Only 25% of oral retinoid dispensings had evidence of concomitant contraceptive use in 2021.

Rather than a single fix, the authors of that study said there are likely to be multiple solutions to this problem.

“A clinical pathway is needed for reproductive-aged women to obtain both oral retinoids and effective contraception. Options may include GPs prescribing both medications, or dermatologists only prescribing oral retinoids when there’s a contraception plan already in place. Some women may initially not be sexually active, but change their sexual behaviour while taking oral retinoids, so constant reminders and education are likely to be required.

Further, contraception access needs to be improved in Australia. Teenagers and young women in particular face barriers to accessing contraception, including costs, stigma and lack of knowledge”, they stated.

Category X drugs dispensed to women aged 15-49 between 2013 and 2021