Olsalazine, an anti-inflammatory medicine, is used to treat ulcerative colitis, a condition in which the bowel is inflamed. Olsalazine reduces the bowel inflammation, diarrhea (stool frequency), rectal bleeding, and abdominal pain.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Ondansetron is used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, anesthesia, and surgery.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Orlistat is used with a low-calorie diet to help you lose weight and to maintain your weight after weight loss. Orlistat is used in patients with a certain weight who may also have high blood pressure, diabetes, high cholesterol, or heart disease.

Orlistat is in a class of drugs called lipase inhibitors. It works in your intestines, where it blocks some of the fat you eat from being absorbed and disgested. This undigested fat is then removed in your bowel movements (BM).

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Olopatadine is used to treat the symptoms of allergic pink eye. Olopatadine is in a class of medications called antihistamines. It works by blocking histamine, a substance in the body that causes allergic symptoms.

Olmesartan is used alone or in combination with other medications to treat high blood pressure. Olmesartan is in a class of medications called angiotensin II receptor antagonists. It works by blocking the action of certain chemicals that tighten the blood vessels, so blood flows more smoothly.

Oxybutynin transdermal patches are used to treat an overactive bladder (a condition in which the bladder muscles contract uncontrollably and cause frequent urination, urgent need to urinate, and inability to control urination). Oxybutynin is in a class of medications called anticholinergics. It works by relaxing the bladder muscles to prevent urgent, frequent, or uncontrolled urination.

Oxazepam is used to relieve anxiety. It also is used to control agitation caused by alcohol withdrawal.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Oxybutynin is used to relieve urinary and bladder difficulties, including frequent urination and inability to control urination. It also helps to decrease muscle spasms of the bladder.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Oxiconazole, an antifungal agent, is used to treat skin infections such as athlete's foot, jock itch, and ringworm.

This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.

Octreotide ( ok-TREE-oh-tide) is used to treat the severe diarrhea and other symptoms that occur with certain intestinal tumors. It does not cure the tumor but it helps the patient live a more normal life.

Also, this medicine is used to treat a condition called acromegaly, which is caused by too much growth hormone in the body. Too much growth hormone produced in adults causes the hands, feet, and parts of the face to become large, thick, and bulky. Other problems such as arthritis also can develop. Octreotide works by reducing the amount of growth hormone that the body produces.

Octreotide may also be used for other medical conditions as determined by your doctor.

Octreotide is available only with your doctor's prescription, in the following dosage form:

Parenteral
• Injection (U.S. and Canada)

Omeprazole (o-MEP-ra-zole ) is used to treat certain conditions in which there is too much acid in the stomach. It is used to treat gastric and duodenal ulcers and gastroesophageal reflux disease, a condition in which the acid in the stomach washes back up into the esophagus. Sometimes omeprazole is used in combination with antibiotics to treat ulcers associated with infection caused by the H. pylori bacteria (germ).

Omeprazole is also used to treat Zollinger-Ellison disease, a condition in which the stomach produces too much acid.

Omeprazole is also used to treat dyspepsia, a condition that causes sour stomach, belching, heart burn, or indigestion.

In addition, omeprazole is used to prevent upper gastrointestinal tract bleeding in seriously ill patients.

Omeprazole works by decreasing the amount of acid produced by the stomach.

This medicine is available only with your doctor's prescription.

Oral
• Delayed-release capsules (U.S.)
• Powder for oral suspension (U.S.)
• Delayed-release tablets (Canada)

Opium preparations are used along with other measures to treat severe diarrhea. These medicines belong to the group of medicines called narcotics. If too much of a narcotic is taken, it may become habit-forming, causing mental or physical dependence. Physical dependence may lead to withdrawal side effects when you stop taking the medicine.

Opium preparations are available only with your doctor's prescription, in the following dosage forms:

Oral
• Opium Tincture
  • Oral liquid (U.S. and Canada)
• Paregoric
  • Oral liquid (U.S. and Canada)

Orphenadrine and aspirin ( or-FEN-a-dreen and AS-pir-in) combination is used to help relax certain muscles in your body and relieve the pain and discomfort caused by strains, sprains, or other injury to your muscles. However, this medicine does not take the place of rest, exercise, or other treatment that your doctor may recommend for your medical problem.

Orphenadrine acts in the central nervous system (CNS) to produce its muscle relaxant effects. Actions in the CNS may also be responsible for some of its side effects. Orphenadrine also has other actions (antimuscarinic) that may be responsible for some of its side effects.

This combination medicine also contains caffeine ( kaf-EEN) .

In the U.S., this combination medicine is available only with your doctor's prescription. In Canada, it is available without a prescription.

These medicines are available in the following dosage forms:

Oral
• Tablets (U.S. and Canada)

Oxtriphylline and guaifenesin ( ox-TRYE-fi-lin and gwye-FEN-e-sin ) combination is used to treat or prevent the symptoms of asthma or to treat chronic bronchitis and emphysema. This medicine relieves cough, wheezing, shortness of breath, and troubled breathing. It works by opening up the bronchial tubes (air passages of the lungs) and increasing the flow of air through them.

This medicine is available only with your doctor's prescription, in the following dosage form:

Oral
• Elixir (U.S. and Canada)

Oxymetazoline (ox-i-met-AZ-oh-leen) is used for the temporary relief of nasal (of the nose) congestion or stuffiness caused by hay fever or other allergies, colds, or sinus trouble.

This medicine may also be used for other conditions as determined by your doctor.

This medicine is available without a prescription; however, your doctor may have special instructions on the proper use or dose for your medical condition.

Oxymetazoline is available in the following dosage forms:

Nasal
• Nasal drops (U.S.)
• Nasal spray (U.S. and Canada)

Oxytocin (ox-i-TOE-sin) is a hormone used to help start or continue labor and to control bleeding after delivery. It is also sometimes used to help milk secretion in breast-feeding.

Oxytocin may also be used for other conditions as determined by your doctor.

In general, oxytocin should not be used to start labor unless there are specific medical reasons. Be sure you have discussed this with your doctor before receiving this medicine.

Oxytocin is available only with your doctor's prescription, in the following dosage forms:

Nasal
• Solution (U.S. and Canada)

Parenteral
• Injection (U.S. and Canada)

Ofloxacin (oh-FLOKS-a-sin) is an antibiotic used to treat bacterial infections of the eye, such as conjunctivitis and corneal ulcers.

Ofloxacin is available only with your doctor's prescription, in the following dosage form:

Ophthalmic
• Ophthalmic solution (eye drops) (U.S. and Canada)

Ofloxacin ( oh-FLOX-a-sin) belongs to the family of medicines called antibiotics. Ofloxacin otic solution is used to treat infections of the ear canal. It also is used to treat infections of the middle ear in patients with nonintact tympanic membranes (holes or tubes in the eardrums).

This medicine is available only with your doctor's prescription, in the following dosage form:

Otic
• Otic solution (eardrops) (U.S.)

Olanzapine (oh-LAN-za-peen ) is used to treat psychotic mental disorders, such as schizophrenia, bipolar disorder, and agitation that occurs with schizophrenia and bipolar mania. This medicine should NOT be used to treat behavioral problems in older adult patients who have dementia.

This medicine is available only with your doctor's prescription, in the following dosage form:

Oral
• Oral disintegrating tablets (U.S.)
• Tablets (U.S.)

Parenteral
• Injection (U.S.)

Oseltamivir ( Oh-sel-TAM-i-veer) belongs to the family of medicines called antivirals, which are used to treat infections caused by viruses. Oseltamivir is used in the treatment of the infection caused by the flu virus (influenza A and influenza B). Oseltamivir may reduce flu symptoms (weakness, headache, fever, cough, and sore throat) by 1 day. Oseltamivir has also been shown to prevent influenza infection if you have come into close contact with someone who has the flu.

If you receive the flu vaccine every year, continue to do so.

Oseltamivir is available only with your doctor's prescription in the following dosage form:

Oral
• Capsules (U.S. and Canada)
• Oral suspension (U.S.)

Olmesartan ( ohl-me-SAR-tan) belongs to the class of medicines called angiotensin II inhibitor antihypertensives. It is used to treat high blood pressure (hypertension).

High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may not function properly. This can damage the blood vessels of the brain, heart, and kidneys, resulting in a stroke, heart failure, or kidney failure. High blood pressure also may increase the risk of heart attacks. These problems may be less likely to occur if blood pressure is controlled.

Olmesartan works by blocking the action of a substance in the body that causes blood vessels to tighten. As a result, olmesartan relaxes blood vessels. This lowers blood pressure.

This medicine is available only with your doctor's prescription, in the following dosage form(s):

Oral
• Tablets (U.S.)

Omalizumab ( oh-mah-lye-ZOO-mab) is used to treat moderate to severe persistent allergic asthma. Omalizumab is a shot (injection) given under the skin (subcutaneous) The shot is given every 2 or 4 weeks. For many patients who still have asthma symptoms even though they are taking inhaled steroids, omalizumab helps to reduce the number of asthma attacks.

Omalizumab is a medicine called an IgE blocker. IgE is short for immunoglobulin E. IgE is a substance that occurs naturally in the body in small amounts. This substance plays an important role in allergic asthma. When people with allergic asthma breathe in a year-round allergen, such as cat or dog dander, their bodies make more IgE. This may cause a series of reactions in your body that can lead to asthma attacks and symptoms. Omalizumab works by helping to block IgE.

This medicine is available only with your doctor's prescription, in the following dosage forms:

Parenteral
• Injection (U.S.)