Health Canada is warning people who bought unauthorized products from amazon.ca labelled to contain the prescription drugs tryptophan or lithium to be aware of serious health risks.

L‑tryptophan is prescribed in combination with antidepressants for patients with depressive disorders. Lithium is approved to treat manic episodes of manic-depressive illness.

Health Canada said Wednesday that multiple unauthorized products labelled to contain L-tryptophan at doses higher than the approved prescription strength of 220 milligrams per day and lithium orotate were sold online.

Amazon has removed these products from its website as requested by the regulator.

Both medications should only be used only under the supervision of a health care professional.

"Individuals taking these products should consult with their health care professional to receive advice on safely discontinuing use of these products, and on appropriate treatment for their medical condition," Health Canada said in its advisory.

Stick with licensed pharmacies

Health Canada assesses drugs for safety, effectiveness and quality before approval of sale, including internet sales.

The regulator advises people to buy prescription drugs only from licensed pharmacies.

"Consumers who take a prescription drug without being examined and monitored by a health care professional may not receive appropriate treatment. They may also put themselves at risk for harmful drug interactions and dangerous side-effects," Health Canada says.

Consumers are advised to read the label to verify a product has been authorized for sale by looking for an eight-digit Drug Identification Number (DIN), Natural Product Number (NPN) or Homeopathic Drug Number (DIN-HM).

Health Canada's Drug Product Database and Licensed Natural Health Product Database are two other sources consumers may search to check.

The regulator's advisory also listed side-effects of L-tryptophan, which include:

Dry mouth.

Dizziness.

Nausea.

Headache.

Sexual problems.

It says that in rare cases when taken with other drugs that affect the central nervous system, a potentially life-threatening reaction called serotonin syndrome can occur. Symptoms of the syndrome include high temperature, agitation, sweating, rapid heart rate and high blood pressure, muscle rigidity, confusion, and seizures.

Common lithium side-effects include increased thirst and urination, hand tremors and drowsiness. Severe dehydration has been reported. Intoxication can occur, especially when taken with other medications.