Feb. 22 (iVillage Total Health) -- The U.S. Food and Drug Administration (FDA) is warning consumers about the possible dangers of buying drugs online after receiving reports of several people who were sent bogus medications.

The latest case involves people who ordered several different types of medications from Internet Web sites. The drugs included commonly prescribed medications such as the sleep medication Ambien, the antidepressant Lexapro and the anti-anxiety medications Xanax and Ativan. According to the FDA, instead of receiving the requested medications, consumers got products that contained haloperidol, a powerful antipsychotic drug and the active ingredient in a prescription medication commonly used to treat schizophrenia . According to the FDA, haloperidol can cause muscle stiffness and spasms, agitation and sedation.

After taking the drugs, several people reported experiencing breathing difficulty and muscle spasms and stiffness. All sought medical attention. The FDA is conducting laboratory tests of the medications reported by consumers. Preliminary analysis of some of the drugs shows they contain haloperidol.

Investigators are attempting to trace the medications back to the original manufacturers, but so far the origin of the tablets is unknown. The packages containing the medications were postmarked in Greece. However, many Internet products are difficult to trace because of deceptive practices sometimes used by online vendors, according to the FDA.

To report a suspicious product to the FDA, go to https://www.accessdata.fda.gov/scripts/medwatch/medwatch-online.htm.

The FDA advises consumers to visit its Web site at http://www.fda.gov/buyonline/ before purchasing medications online.

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