LONDON — Poison ivy can kill a person in five to 15 days, a new study has found, and a toxic cocktail of medications could not be found for treatment of people with cancer who were treated with it in the past.

The study, published online Tuesday in the journal Lancet, also found that the most effective drugs are only effective for a short time and could not save many people.

The toxic cocktail included three classes of drugs called thiomersal, clindamycin and pyrimethamine, which all target specific genes, and have been shown to kill cancer cells.

The studies, funded by the British Medical Research Council, looked at cases of patients with cancer treated with the poisons.

They are:Thiomersals are the most powerful, according to the researchers.

They can kill cells for up to a year and cause a range of side effects including skin, liver and bone pain.

The most common side effect is skin rash and the liver can break down the toxic drugs.

Clindamycins can kill cancer cell lines for a month or more.

They are less toxic than thiomerals but they can cause more serious side effects, such as liver damage.

Pyrimethans are the second most powerful of the thiomedicines, according a statement from the British medical research council.

They kill cells in less than two weeks and have shown limited success in killing cancer cells in mice.

They also cause less toxicity than clindamys and pyranthenes, but have a greater risk of causing liver damage, the statement said.

The last of the three classes, clitosan, kills cells within weeks and has been shown in animals to be safe.

It has been tested in mice but the results have not yet been published in humans.

“These drugs are incredibly potent,” said Dr. Jens-Peter Bäckhed, director of the Leiden University Cancer Center and lead author of the study.

“These drugs may be very safe, but they could not provide much hope for survival.

The toxicity of the drugs would need to be assessed in future clinical trials to be able to assess the benefits of them in patients with severe cases of cancer.”

Dr. Bäcker said there is no reason why patients should not receive an extra dose of clindamin, clinolizumab or clopidogrel, which are also effective against cancer.

The authors said their findings showed that the toxic cocktail might not be as effective in cancer patients as it was in people with a rare genetic mutation known as CJD1, which is responsible for more than 95 percent of cases of the disease.

CJD-1 is thought to cause about 80 percent of cancers in adults and about 50 percent in children.

More than two decades ago, scientists were able to use the genes of CJD patients to create a pill called the CJD5 gene-therapy pill, which was supposed to treat the genetic disease.

They found it was extremely effective against the virus, but could not treat people with other diseases.