Zaditen is a brand of eye drops used to relieve the symptoms of allergic conjunctivitis. The active ingredient is ketotifen.

For more information, see Zaditen. 

Zanamivir is a drug used in the treatment and prevention of influenza type A and B viruses, including avian influenza and swine flu. Zanamivir is currently marketed as Relenza.

For more information, see Relenza.

Zinc is a micronutrient that is necessary for the human body to function normally. Zinc helps maintain the structural integrity of proteins and regulates gene expression (how genes and genetic traits are replicated in the DNA).

Zinc is found in a wide variety of foods. The majority of zinc in the diet comes from animal products, especially meat, fish and poultry, but also vegetables and dairy products.

In the human body, zinc is mainly stored in bones and muscle tissues. A deficiency in zinc is associated with poor pregnancy and infant outcomes.

For more information, see Vitamin and Mineral Requirements and Supplements During Pregnancy.

Zollinger–Ellison syndrome is a rare condition in which excessive gastric acid leaves the stomach as a result of pancreatic cancer. Individuals with this condition often also have peptic ulcers. It results from excessive production of the hormone gastrin, which is responsible for the production of gastric acid.

For more information, see Zollinger–Ellison Syndrome.

Zolmitriptan is one of a group of medicines called triptans which belong to the class of medicines called selective serotonin reuptake inhibitors (SSRIs). It is used to treat headaches, including migraine and cluster headaches. It works by reducing swelling in the blood vessels of the brain and blocking the release of chemicals involved in pain responses.

Zoloft belongs to the class of drugs called the selective serotonin reuptake inhibitors (SSRIs) and is used to treat depression, premenstrual dysphoric disorder (PMDD), obsessive compulsive disorders (OCD), panic disorders and social phobias.

Zostavax is a vaccine used to prevent shingles in people over 50 years of age. Shingles is a condition that affects adults who have previously had chicken pox infection (either from vaccination or wild disease). It is caused by the same virus as chicken pox. Zostavax boosts an individual's immunity to chicken pox, and in doing so helps to prevent shingles.

For more information, see Zostavax Powder for Injection.

Zoster Immunoglobulin-VF is a product made from human blood which contains antibodies that fight against chicken pox. When injected into a person's body, the antibodies begin fighting varicella virus in that person. Zoster Immunoglobulin-VF is given to individuals with weak immune systems who have been exposed to someone with active chicken pox, and are at very high risk of developing chicken pox themselves.

For more information, see Zoster Immunoglobulin-VF Solution for Injection.

The zygomaticus major is a muscle involved in facial expression, particularly smiling.