WASHINGTON, D.C. ( TheStreet) --The U.S. Food and Drug Administration approved two drugs Tuesday night -- a prescription drug for a rare, genetic disorder and an over-the-counter treatment for heartburn.

The FDA also rejected Hemispherx BioPharma's ( HEB - Get Report) drug for chronic fatigue syndrome. (Read about Ampligen's setback here.)

Dyax ( DYAX) received full approval to market Kalbitor for the treatment of acute attacks of hereditary angiodema (HAE), a rare genetic disorder that causes severe and painful swelling in various parts of the body.

As a condition of the FDA approval, Dyax is required to set up a risk management program to warn patients that Kalbitor can cause severe allergic reactions.

Kalbitor is the second drug approved to treat HAE attacks. In October, CSL Behring's drug Berinert also received the FDA 's blessing, although approval was limited to patients who suffer HAE attacks in the abdomen and face. Viropharma ( VPHM) also markets a drug to prevent HAE attacks from occurring.

Dyax shares hit $5 in after-hours trading Tuesday after closing the regular session at $3.50.

FDA also approved an over-the-counter version of the heartburn medicine Zegerid marketed by Merck ( MRK - Get Report). The drug utilizes technology from Santarus ( SNTS), which will receive $20 million for the Zegerid OTC approval plus a low, double-digit royalty on sales.

Zegerid OTC contains a 20 mg dose of the medicine omeprazole (the active ingredient in Prilosec.) Santarus continues to sell a 40 mg version of Zegerid that contributes about 95% of prescriptions for the drug.

Santarus shares closed Tuesday at $4.29 but surged 36% in the after-hours session.

-- Reported by Adam Feuerstein in Boston

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