• Question: Which out of efficacy, dosage and toxicity are the most important when testing the safeness of drugs

    Asked by anon-220247 to Rachel on 7 Jun 2019.
    • Photo: Rachel Hardy

      Rachel Hardy answered on 7 Jun 2019:

      Hey, great question 🙂 ! All 3 of these are extremely important factors that need to be considered when developing a new drug. However, toxicity and dosage are most important when referring to the safety of drugs. The ‘toxicity’ of a drug refers to any bad or ‘toxic’ effect that the drug causes (these effects may involve any organ in the body, but are most commonly associated with the heart and liver). For example, a drug may cause a decrease in the ability of the heart to pump blood effectively. Usually, the benefit vs risk profile of a drug is considered when making a decision whether or not to continue developing a drug. If a drug is likely to kill someone or make them seriously unwell, it will not be taken any further. However, if a drug is likely to cause some bad side-effects, but is the best treatment available for a certain disease (e.g. a new drug to increase the survival time of a terminal cancer), this may still be considered. The dose of a drug is strongly linked with its toxicity. Any drug given at too high a dose will likely result in toxic effects in patients. When new drug is being developed, scientists in the lab aim to find out what dose of a drug is toxic, and what dose of a drug is needed for it to be effective. Obviously we can’t give drugs at a certain dose if they will be toxic, but they also still need to be given in a dose which can treat the disease.

      I hope this helps to answer your question. Efficacy is still an important consideration after drug safety testing. This basically refers to how effective the drug is at treating the disease. If the results of safety testing show that the drug is safe in a low dose, but this dose is not effective, there is no point developing it further. The whole drug discovery process is often a delicate balance of efficacy vs toxicity 🙂

Comments

  • Photo: Alex

    Alex commented on :

    Clinical trials for testing new drugs are carried out in phases, where each phase is looking at a different outcome as priority. The first phase of testing is usually very small scale and carried out on healthy people, as a way to test the toxicity of the drug on humans. Once this has been established to be low/acceptable, phase 2 can begin.

    The second phase is usually used for both proof of concept and/or determining correct dosing. Therefore patients may be assigned different doses of the drug to determine which is best with respect to both evidence of efficacy and also keeping side effects to a minimum.

    The third stage of testing is a large scale phase 3 trial (this is where my research is focused). This is where the chosen dose of the drug is conducted on a large scale, and compared with a control (e.g. a placebo, or the current standard of care on the NHS). Here, randomisation is particularly important since we are primarily measuring efficacy (how good the drug is) so it’s crucial we carry out the experiment to ensure a fair comparison. After this phase is complete, if there is evidence the drug works the drug can be submitted to regulatory approval, where the results of all the phases will be evaluated.
    So in short, efficacy, toxicity and dosing are all important aspects to measure in drug trials, and approval will always be based on a combination of these things.