SIDE EFFECTS: Diarrhea is a common side effect of this medication. If you have diarrhea, ask your doctor or pharmacist about ways to lessen this side effect, such as using anti-diarrhea medicine. Nausea or gas may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Some people may experience worsening of a previous medical condition (such as an old infection) as their immune systems improve, or develop new conditions because their immune systems have become overactive. This reaction may occur at any time (soon after starting HIV treatment or many months later). Tell your doctor right away if you have any serious side effects, including: unexplained weight loss, persistent muscle aches/weakness, joint pain, numbness/tingling of the hands/feet/arms/legs, severe tiredness, vision changes, severe/persistent headaches, signs of infection (such as fever, chills, trouble breathing, cough, non-healing skin sores), signs of an overactive thyroid (such as irritability, nervousness, heat intolerance, fast/pounding/irregular heartbeat, bulging eyes, unusual growth in the neck/thyroid known as a goiter), signs of a certain nerve problem known as Guillain-Barre Syndrome (such as difficulty breathing/swallowing/moving your eyes, drooping face, paralysis, slurred speech).

Seek immediate medical attention if any of these rare but serious side effects occur: symptoms of a heart attack (such as chest/jaw/left arm pain, shortness of breath, unusual sweating), easy bruising/bleeding, persistent nausea/vomiting, stomach/abdominal pain, dark urine, yellowing eyes/skin.

This medication may infrequently make your blood sugar level rise, which can cause or worsen diabetes. Tell your doctor immediately if you develop symptoms of high blood sugar such as increased thirst and urination. If you already have diabetes, check your blood sugar levels regularly. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Changes in body fat may occur while you are taking this medication (such as increased fat in the upper back and stomach areas, decreased fat in the arms and legs). The cause and long-term effects of these changes are unknown. Discuss the risks and benefits of treatment with your doctor, as well as the possible use of exercise to reduce this side effect.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the Viracept (nelfinavir mesylate) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: Before taking nelfinavir, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: diabetes, heart problems (coronary artery disease, heart attack), lipid problems (high cholesterol or triglycerides/fats), hemophilia, liver problems.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Children may be more sensitive to the side effects of this drug, especially diarrhea or rash.

Tell your doctor if you are pregnant before using this medication.

It is unknown if this medication passes into breast milk. Because breast milk can transmit HIV, do not breast-feed.