Nelfinavir belongs to a group of medications called protease inhibitors. It is used in combination with other medications to treat human immunodeficiency virus (HIV) infection. HIV is the virus responsible for acquired immune deficiency syndrome (AIDS). HIV infection destroys CD4 (T) cells, which are important to the immune system and the immune system helps fight infections.

Protease is an enzyme that is needed by HIV to reproduce. Nelfinavir blocks the action of protease to decrease the amount of HIV in the blood.

This medication does not cure HIV infection of AIDS and does not prevent it from being spread to others. It does slow further growth or reproduction of HIV when used in combination with other drugs and seems to slow down the destruction of the immune system. This may help to delay the development of problems that are related to AIDS or HIV infection.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended adult dose of nelfinavir is 750 mg 3 times a day with food or 1,250 mg 2 times a day. The maximum daily dose is 2,500 mg.

The recommended dose for children ages 2 to 13 are based on body weight and calculated by the doctor. The usual dose is 25 mg to 30 mg per kilogram of body weight 3 times a day with food. For children under 2 years of age, the decision to use nelfinavir and the dose must be determined by the doctor.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

People who cannot swallow the tablets whole may crush the tablet to mix with food or disperse the tablet in water. The entire contents of the food or fluid must be consumed to make sure the entire dose is received.

The oral powder is available for children's doses. It is important to use a measuring spoon that is marked to give an accurate measurement. The powder may be mixed with milk or formula and stored in the refrigerator for up to 6 hours, if necessary.

Nelfinavir should be taken with food. If it is crushed and mixed with food or water, acidic foods or juices  (e.g., apple sauce, orange juice) are not recommended as this results in a bitter tasting mixture.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from moisture, and keep it out of reach of children.

Do not take this medication if you:

• are allergic to nelfinavir or any ingredients of the medication
• are taking any of the following medications:
• alfuzosin
• amiodarone
• cisapride
• ergot derivatives (dihydroergotamine, ergonovine, ergotamine, methylergonovine)
• lovastatin
• lurasidone
• midazolam
• pimozide
• quinidine
• rifampin
• sildenafil (when used for treatment of pulmonary arterial hypertension)
• simvastatin
• St. John's wort
• triazolam

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• diarrhea
• gas
• loss of appetite
• nausea
• skin rash
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• changes in fat distribution (increased fat in the upper back and neck, breasts, and trunk; loss of fat from the arms, legs, and face)
• signs of bleeding (e.g., bloody nose, blood in urine, coughing blood, cuts that don't stop bleeding, blood in stools)
• signs of infections (e.g., fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a serious allergic reaction (e.g., swelling of face or throat, hives, or difficulty breathing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Birth control: Birth control pills may be less effective while you are taking this medication. Talk to your doctor or pharmacist about appropriate methods of birth control.

Body fat changes: People using nelfinavir may notice the accumulation and redistribution of fat in their body. For example, less body fat on their arms, legs, and face, and more around the centre of their body (e.g., enlarged breasts, abdominal or central obesity, and a "buffalo hump" - a pad of fat on the back). The cause or long-term health effects of these conditions are not known at this time.

Diabetes: Nelfinavir may cause diabetes or increase blood sugar levels. People with diabetes should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience symptoms of diabetes such as frequency urination or increased thirst, contact your doctor. If you have diabetes and your blood sugar control worsens, contact your doctor.

Hemophilia: Nelfinavir may put people with hemophilia at a higher risk of bleeding while taking this medication. People with hemophilia should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Immune reconstitution syndrome: This medication may cause immune reconstitution syndrome, where signs and symptoms of inflammation from previous infections appear. These symptoms occur soon after starting anti-HIV medication and can vary. They are thought to occur as a result of the immune system improving and being able to fight infections that have been present without symptoms (such as pneumonia, herpes, or tuberculosis). Report any new symptoms to your doctor immediately.

Liver function: Nelfinavir is broken down by the liver. Liver disease or reduced liver function may cause nelfinavir to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Other medications: Nelfinavir may interact with a number of medications, which may mean a change in how you take this medication (See "What medications can interact with this medication?"). Tell your doctor of all medications that you are taking. Certain medications should not be taken with nelfinavir at all (see "Who should NOT take this medication?"). Nelfinavir should never be used on its own and should always be used in combination with other HIV medications.

Phenylketonuria: People with phenylketonuria (a condition where the body cannot break down phenylalanine) should be aware that the oral powder form of nelfinavir contains 11.2 mg of phenylalanine per gram of powder.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if this medication passes into breast milk. However, breast-feeding is not recommended for women who are HIV-positive, as HIV can be transmitted to the baby through infected mothers' milk.

Children: The safety and effectiveness of using this medication have not been established for children under 2 years of age. Children under 2 years of age should not use this medication unless the benefits outweigh the risks.

There may be an interaction between nelfinavir and any of the following:

• abiraterone acetate
• alfuzosin
• amiodarone
• aprepitant
• apixaban
• aripiprazole
• "azole" antifungals (e.g., fluconazole, itraconazole, ketoconazole)
• birth control pills
• bisoprolol
• boceprevir
• bosentan
• bromocriptine
• calcitriol
• calcium channel blockers (e.g., amlodipine, diltiazem, nicardipine, nifedipine, verapamil)
• carbamazepine
• certain benzodiazepines (e.g., alprazolam, clonazepam, diazepam, midazolam, triazolam)
• certain protein kinase inhibitors (e.g., crizotinib, dabrafenib, imatinib)
• clozapine
• cobicistat
• colchicine
• conivaptan
• corticosteroids, inhaled (e.g., budesonide, fluticasone propionate)
• corticosteroids, oral (e.g., dexamethasone, methylprednisolone)
• cyclophosphamide
• cyclosporine
• daclatasvir
• dapsone
• darifenacin
• dasatanib
• deferasirox
• diabetes medications (e.g., chlorpropamide, glipizide, glyburide, insulin, , rosiglitazone)
• digoxin
• dipyridamole
• disopyramide
• divalproex
• domperidone
• docetaxel
• doxorubicin
• dronedarone
• dutasteride
• enzalutamide
• eplerenone
• ergot derivatives (e.g., dihydroergotamine, ergoloid mesylates, ergonovine, ergotamine, methylergonovine)
• etoposide
• everolimus
• famotidine
• grapefruit juice
• guanfacine
• ifosfamide
• irinotecan
• lidocaine
• lomitapide
• lurasidone
• macrolide antibiotics (e.g., azithromycin, erythromycin, clarithromycin, telithromycin)
• maraviroc
• mefloquine
• mirabegron
• mirtazapine
• naloxegol
• nefazodone
• nitrates (e.g., isosorbide dinitrate, isosorbide mononitrate)
• nizatidine
• opioid narcotics (e.g., cocaine, fentanyl, methadone, oxycodone)
• paclitaxel
• phenobarbital
• phenytoin
• phosphoesterase-5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
• pimozide
• primidone
• procainamide
• other protease inhibitors (e.g., daraunavir, indinavir, lopinavir, ritonavir, saquinavir)
• oxybutynin
• phenytoin
• pimecrolimus
• prasugrel
• primaquine
• progestins (e.g., dienogest, levonorgestrel, medroxyprogesterone, norethindrone)
• propranolol
• proton pump inhibitors (e.g., esomeprazole, omeprazole, pantoprazole)
• quetiapine
• quinidine
• quinine
• quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
• ranitidine
• reverse transcriptase inhibitor (e.g., delaviradine, efavirenz)
• rifabutin
• rifampin
• romidepsin
• salmeterol
• selective serotonin reuptake inhibitors (SSRIs; e.g., escitalopram, citalopram)
• serotonin antagonists (anti-emetic medications; e.g., granisetron, ondansetron)
• silodosin
• simeprevir
• sirolimus
• solifenacin
• sotalol
• St. John's wort
• "statin" anticholesterol medications (e.g., atorvastatin, fluvastatin, lovastatin, simvastatin)
• tacrolimus
• tamoxifen
• tamsulosin
• tetrabenazine
• theophylline
• ticagrelor
• tizanidine
• tolterodine
• tolvaptan
• tramadol
• trastuzumab
• trazodone
• tricyclic antidepressants (e.g., amitriptyline, imipramine)
• "triptan" migraine medications (e.g., naratriptan, sumatriptan)
• ulipristal
• venlafaxine
• vinca alkaloids (e.g., vinblastine, vincristine, vinorelbine)
• warfarin
• zidovudine
• zolpidem
• zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.