)Unknown frequency

Anemia
Headache
Increased respiratory rate
Orthostatic hypotension
Prolonged QT interval
Visual disturbancesRare (<1% incidence)

Contraindications
Pre-existing coma, acute stroke
Severe intoxication with alcohol or other central depressant drugs
Known allergy against haloperidol or other butyrophenones or other drug ingredients
Known heart disease, when combined will tend towards cardiac arrest

Special cautions
A multiple-year study suggested this drug and other neuroleptic antipsychotic drugs commonly given to people with Alzheimers with mild behavioral problems often make their condition worse and its withdrawal was even beneficial for some cognitive and functional measures. Elderly patients with dementia-related psychosis: analysis of 17 trials showed the risk of death in this group of patients was 1.6 to 1.7 times that of placebo-treated patients. Most of the causes of death were either cardiovascular or infectious in nature. It is not clear to what extent this observation is attributed to antipsychotic drugs rather than the characteristics of the patients. The drug bears a boxed warning about this risk. Impaired liver function, as haloperidol is metabolized and eliminated mainly by the liver
In patients with hyperthyroidism, the action of haloperidol is intensified and side effects are more likely. IV injections: risk of hypotension or orthostatic collapse
Patients at special risk for the development of QT prolongation (hypokalemia, concomitant use of other drugs causing QT prolongation)
Patients with a history of leukopenia: a complete blood count should be monitored frequently during the first few months of therapy and discontinuation of the drug should be considered at the first sign of a clinically significant decline in white blood cells.
The mean T1/2 is 20.7 hours. The decanoate injectable formulation is for intramuscular administration only and is not intended to be used intravenously. The plasma concentrations of haloperidol decanoate reach a peak at about six days after the injection, falling thereafter, with an approximate half-life of three weeks. Intravenous injections
The bioavailability is 100% in intravenous (IV) injection, and the very rapid onset of action is seen within seconds. The T1/2 is 14.1 to 26.2 hours. The apparent volume of distribution is between 9.5 and 21.7 L/kg. The duration of action is four to six hours. Therapeutic concentrations
Plasma levels of five to 15 micrograms per liter are typically seen for therapeutic response (Ulrich S, et al. Clin Pharmacokinet. 1998). The determination of plasma levels is rarely used to calculate dose adjustments but can be useful to check compliance. The concentration of haloperidol in brain tissue is about 20-fold higher compared to blood levels. It is slowly eliminated from brain tissue,  which may explain the slow disappearance of side effects when the medication is stopped. Distribution and metabolism
Haloperidol is heavily protein bound in human plasma, with a free fraction of only 7.5 to 11.6%. It is also extensively metabolized in the liver with only about 1% of the administered dose excreted unchanged in the urine. The greatest proportion of the hepatic clearance is by glucuronidation, followed by reduction and CYP-mediated oxidation, primarily by CYP3A4. History
Haloperidol was discovered by Paul Janssen.