Merck joins the rosters of pharmaceutical companies like Hoffmann La Roche that make drugs that, if they don’t kill you, at least will drive you crazy. Roche has specialized for years in making drugs with psychiatric side effects like depression and suicidality, including Accutane (acne), larium (malaria), and Tamiflu (bird flu). Chantix (smoking cessation, Pfizer) has also led to some pretty trippy experiences amongst users. No wonder when you take a drug that affects the frontal lobe of the brain. However, mefloquine (Larium), with over half of people who take it developing psychiatric symptoms. In 2009 the FDA asked manufacturers of asthma drugs like Singulair and Accolate to add neuropsychiatric side effects to the warning label. From the FDA website:
The reported neuropsychiatric events include postmarket cases of agitation, aggression, anxiousness, dream abnormalities and hallucinations, depression, insomnia, irritability, restlessness, suicidal thinking and behavior (including suicide), and tremor.
Montelukast (Singulair), zafirlukast (Accolate) and zileuton (Zyflo) are part of a new generation of asthma medications that are leukotriene antagonists. These medications work by inhibiting the cysteinyl leukotriene
CysLT-1 receptor, which is involved in the inflammatory response. Side effects include headache, gastritis, runny nose, dizziness, nausea, stomach pain, joint pain, and fever. In rare cases they may be associated with Churg-Strauss syndrome, which involves inflammation of the blood vessels.
There are leukotriene receptors in the brain, and since this drug binds to this receptor and since depression is mediated through the brain, this suggests a mechanism by which Singulair could cause depression.
You can read my book about my experiences as an expert witness in drug safety litigation related to the acne medication Accutane and suicide The Goose That Laid the Golden Egghere.