Relief from nasal congestion caused by allergies or the common cold may be found through the use of pseudoephedrine hydrochloride, an over-the-counter medication 4. This nasal decongestant works by constricting the flow of blood through the nasal passageways. People should review the side effects of pseudoephedrine hydrochloride before beginning treatment with this medication 124.

Restlessness or Difficulty Sleeping

Treatment with pseudoephedrine hydrochloride can cause restlessness or nervousness in certain people, explain health professionals with MedlinePlus 14. People who develop these side effects can appear unusually fidgety or can have difficulty concentrating while at work or school. Restlessness or nervousness can also contribute to difficulties falling asleep or staying asleep through the night. People who experience persistent sleeping difficulties or nervousness should discuss these severe side effects of pseudoephedrine hydrochloride with a medical professional 24.

Upset Stomach

After taking a dose of this nasal decongestant, certain people can develop upset stomach side effects. Affected people can feel nauseous or may begin to vomit, explains sanofi-aventis, a pharmaceutical manufacturer of pseudoephedrine hydrochloride 34. People can limit the development of these stomach upset side effects by avoiding taking this medication on an empty stomach 1.

Headache, Dizziness or Weakness

Episodes of headache, dizziness or weakness can occur in certain people who take pseudoephedrine hydrochloride, according to MayoClinic.com 24. Headache pain is typically mild, but can interfere with a person's ability to remain focused or alert during the day. Dizziness or weakness can cause certain people to appear confused, unstable or disoriented. People who experience severe or persistent dizziness or weakness while taking pseudoephedrine hydrochloride should seek additional care from a physician 4.

Heart Rate or Breathing Abnormalities

Heart rate or breathing abnormalities can arise in certain people taking this nasal decongestant, warn MedlinePlus health professionals. People who develop an unusually slow or irregular heartbeat or experience difficulty breathing during treatment with pseudoephedrine hydrochloride should consult a physician as soon as possible 4.