Voltaren Gel (diclofenac sodium topical gel) is a non steroidal anti inflammatory drug (NSAID) that exhibit anti-imflammatory, analgesic, and antipyretic activities in animal models. It is commonly used for inflammation and pain treatment caused by arthritis.
The action mechanism of Voltaren like other NSAIDs, is not completely understood but may be related to prostaglandin synthetase inhibition.
One of big pharmaceutical company that produced this drug is Novartis.

On December 4, 2009, FDA, Novartis and Endo announce that products which containing Diclofenac Sodium have potential cases of liver necrosis, jaundice, fulminant hepatitis with and without jaundice, and liver failure. Some of these reported cases resulted in fatalities or liver transplantation.

FDA, Novartis and Endo notified all healthcare professional to add new warnings and precautions about the potential for elevation in liver function tests during treatment with all products containing Diclofenac Sodium.

Voltaren contain the sodium salt of Diclofenac.

A study in Pakistan showed that Diclofenac caused acute kidney failure in vultures when they ate the carcasses of animals that had recently been treated with it. Species and individual humans that are drug sensitive are initially assumed to lack genes expressing specific drug detoxification enzymes.

In India, using diclofenac in animals reported to have led to a sharp decline in the vulture population, 95% decline in 2004, 99.9% decline as of 2008.
Vultures eat the carcasses of livestock that have been administered veterinary diclofenac, and are poisoned by the accumulated chemical.
The mechanism is probably renal failure, a known side-effect of diclofenac.

Side effect of Diclofenac Sodium related to Hepatic

Liver damage occurs infrequently, and is usually reversible.
Hepatitis may occur rarely without any warning symptoms and may be fatal.
Patients with osteoarthritis more often develop symptomatic liver disease than patients with rheumatoid arthritis.

Other side effects

Clinical result long term usage up to three years have shown an increased risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke which can be fatal.

Using Voltaren in people with hypertension may lead to onset of new hypertension or worsening of preexisting hypertension either of which may contribute ti the increased incidence of cardiovascular events.

Voltaren and some other NSAIDs can cause serious gastrointestinal adverse event including inflammation, bleeding, ulceration, and perforation of the stomach small intestine, or large intestine, which can be fatal.
These serious adverse events can occur at any time, with/without warning symptoms.

For patients with considerable dehydration, long-term administration of NSAIDs has resulted in renal papillary necrosis and other renal injury such as heart failure, liver dysfunction, those taking diuretics and ACE inhibitors, and the elderly.

Voltaren also should not be given to patients with the aspirin triads. It may occur anaphylactoid reactions especially for asthmatic patients who experience rhinitis with or without nasal polyps, or who exhibit severe, potentially fatal bronchospasm after taking aspirin or other NSAIDs.

Voltaren and other NSAIDs can cause serious skin adverse such as exfoliative dermatitis. Steven-Johnson Syndrome (SJS), and toxic epidermal necrolysis (TEN), which can be fatal.

For pregnant women, it should be avoided because it may cause premature closure of the ductus arteriosus.

Other side effect related to Voltaren and other NSAIDs is Anemia.
This may be due to fluid retention, occult or gross GI blood loss, or an incompletely described effect upon erythropoisesis.