Rather, a causal relation is not a relation between values of variables, but a function of one variable (the cause) on to another (the effect). So, given a system of equations, and a set of variables appearing in these equations, we can introduce an asymmetric relation among individual equations and variables that corresponds perfectly to our commonsense notion of a causal ordering. The system of equations must have certain properties, most importantly, if some values are chosen arbitrarily, the remaining values will be determined uniquely through a path of serial discovery that is perfectly causal. They postulate the inherent serialization of such a system of equations may correctly capture causation in all empirical fields, including physics and economics. Manipulation theories
Some theorists have equated causality with manipulability. Under these theories, x causes y only in the case that one can change x in order to change y. This coincides with commonsense notions of causations, since often we ask causal questions in order to change some feature of the world. For instance, we are interested in knowing the causes of crime so that we might find ways of reducing it. These theories have been criticized on two primary grounds. First, theorists complain that these accounts are circular. Attempting to reduce causal claims to manipulation requires that manipulation is more basic than causal interaction. But describing manipulations in non-causal terms has provided a substantial difficulty. The second criticism centers around concerns of anthropocentrism.
Side effects
Side effects of PPIs in general and lansoprazole in particular may include:
Common: diarrhea, abdominal pain
Infrequent: dry mouth, insomnia, drowsiness, blurred vision, rash, pruritus
Rarely and very rarely: taste disturbance, liver dysfunction, peripheral oedema, hypersensitivity reactions (including bronchospasm, urinary, angioedema, anaphylaxis), photosensitivity, fever, sweating, depression, interstitial nephritis, blood disorders (including leukopenia, leukocytosis, pancytopenia, thrombocytopenia), arthralgia, myalgia, skin reactions including (erythroderma, Stevens–Johnson syndrome, toxic epidermal necrolysis, bullous eruption)PPIs may be associated with a greater risk of hip fractures and Clostridium difficile-associated diarrhea. : 22

Interactions
Lansoprazole interacts with several other drugs, either due to its own nature or as a PPI. PPIs reduce absorption of antifungals (itraconazole and ketoconazole)  and possibly increase digoxin in plasma
Increases plasma concentrations of cilostazol (risk of toxicity)Lansoprazole possibly interacts with, among other drugs:

sucralfate
ampicillin
bisacodyl
clopidogrel
delavirdine
fluvoxamine
iron salts
voriconazole
aminophylline and theophylline
astemizole

Chemistry
It is a racemic 1:1 mixture of the enantiomers dexlansoprazole and levolansoprazole. Dexlansoprazole is an enantiomerically pure active ingredient of a commercial drug as a result of the enantiomeric shift. Lansoprazoles plasma elimination half-life (1.5 h) is not proportional to the duration of the drugs effects to the person (i.e. gastric acid suppression). History
Lansoprazole was originally synthesized at Takeda and was given the development name AG 1749. Takeda patented it in 1984 and the drug launched in 1991. In the United States, it was approved for medical use in 1995. Society and culture
Patents
The lansoprazole molecule is off-patent and so generic drugs are available under many brand names in many countries; there are patents covering some formulations in effect as of 2015. Patent protection expired on 10 November 2009.