EXPERT Q&A: What is hydroxychloroquine?

Q. What is hydroxychloroquine and what is it generally used to treat?

Hydroxychloroquine and chloroquine are antimalarial drugs that are more commonly used in developed countries today to treat the autoimmune diseases rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).

Q. How does it work and why is it being considered as a prevention or treatment for COVID-19?

The mechanism of action of hydroxychloroquine and chloroquine is not fully understood. Amongst other things, it interferes with the orderly breakdown and recycling of cellular components. This appears to play a role in its anti-inflammatory effects in RA and SLE.

Q: What have the trials found so far and what do we know of trials in Australian?

Most trials have been for treatment of established disease. Some early studies were suggestive of benefit, but had low numbers of patients and technical issues. More recent studies have shown no treatment benefit. Furthermore, a Chinese study and a Brazilian study had to be suspended because of toxicity. 

The proposed trial through the Walter and Eliza Hall Institute of Medical Research is a prevention trial. It is possible that hydroxychloroquine, by targeting viral infection, may not be effective in established disease, but may have some protective effects, like the antivirals for influenza, oseltamivir and zanamivir.

Q: It has a significant list of side-effects - is it safe to test the drug or take it as a prevention?

All treatments, including experimental treatments, must balance risks and potential benefits. 

While hydroxychloroquine has significant side effects, our experience with these in treatment of autoimmune disease guide us in the management of its use. Possibly the most important side effect is its effect on the electrical conduction of the heart, leading to potentially lethal arrhythmias. When given to patients with SLE or RA, the patients are screened for heart conduction problems and monitored closely. The problem in COVID is that it appears to have adverse effects on the heart, and may produce heart conduction problems that will make hydroxychloroquine more toxic than in healthy people.

In a prevention trial, where people can be screened for risk factors, are initially healthy, and can be monitored closely, the risks should be similar to patients treated for autoimmune disease. With close monitoring, hydroxychloroquine can be withdrawn if side effects appear.

Q. Are we likely to see a supply issue in Australia as has been reported overseas, especially in the US?

Hydroxycholoquine is a prescription drug in Australia. On March 24, the Therapeutic Goods Administration announced that 'only certain types of specialists will be able to prescribe hydroxychloroquine to new patients'. Given this restriction and expert advice from such groups as Australian Prescriber and the Pharmaceutical Society of Australia, it is unlikely that there will be significant off-label prescribing and supply issues in Australia.