Haloperidol dosage

Zhang-Wong J, Zipursky RB, Beiser M, et al Optimal haloperidol dosage in first-episode psychosis. Can J Psychiatry 44 164—167, 1999... 

The effects of haloperidol dose and plasma concentration and CYP2D6 activity on the QTC interval have been studied in 27 Caucasian patients taking oral haloperidol (aged 23-77 years, dosages 1.5-30 mg/day) (9). Three patients had a QTC interval longer than 456 ms, which can be considered as the cut-off value for a risk of cardiac dysrhythmias. There was no correlation between QTC interval and haloperidol dosage or plasma concentrations or CYP2D6 activity. 

The interaction between haloperidol and rifampicin would appear to be established and clinically important. Be alert for any evidence of reduced haloperidol effects if rifampicin alone is used, and possibly increased effects if isoniazid alone is used. Adjust the haloperidol dosage if necessary. 

The evidence is very limited but be aware that increased haloperidol adverse effects may occur if venlafaxine is also given. It may be necessary to reduce the haloperidol dosage. 

Table 11.1 Dosage of haloperidol (mg/day) prescribed by psychiatrists in Southeast and East Asian countries...

Psychiatrists in Southeast Asia such as Thailand, Malaysia, and Singapore would prescribe 12-14 mg/day of haloperidol while East Asian psychiatrists would prescribe a smaller dose of 9-10 mg/day. The average dose range of haloperidol of 6-10 mg/day was the most commonly prescribed dosage (see Table 11.1). 

HALOPERIDOL Individualize dosage. Children, debilitated, or geriatric patients and those with a history of adverse reactions to neuroleptic drugs may require less haloperidol. 

Haloperidol decanoate injection - Individualize dosage and provide close clinical supervision during initiation and stabilization of therapy. The recommended interval between doses is monthly or every 4 weeks. However, variation in patient response may dictate a need for adjustment of the dosing interval as well as the dose. To determine the minimum effective dose, begin with lower initial doses and adjust the dose upward as needed. 

Initial dosage The initial dose should not exceed 100 mg regardless of previous antipsychotic dose requirements. If the conversion requires more than 100 mg of haloperidol decanoate as an initial dose, administer that dose in 2 injections (maximum of 100 mg initially followed by the balance in 3 to 7 days). 

Intramuscular haloperidol is a suitable drug for tranquillizing violent patients, but it can be difficult to determine the correct dosage, and there is the risk of an acute dystonic reaction, particularly in younger patients. The British National Formulary recommends intramuscular injections of from 2 to 10 mg, subsequent doses being given after 4-8 hours but in exceptional cases, initial doses of up to 30 mg may be necessary. 

Haloperidol is less likely to cause hypotension than chlorpromazine, which has a-adrenoceptor antagonist effects. Both can cause cardiac arrhythmias if used in high dosage or in patients with pre-existing heart disease, or as an idiosyncratic reaction. There have been numerous reports of sudden and unexplained deaths, probably due to cardiac arrhythmia, in patients given chlorpromazine and other neuroleptics. The risk of serious arrhythmia is higher in the obese, and possibly in those of African ancestry. 

A high risk of relapse is inherent to schizophrenic psychoses. A relapse is often triggered by emotional stress. It is very important to prevent a relapse by either maintaining low-dose oral medication or by switching to a depot antipsychotic. In some cases, this cannot be avoided. Especially when compliance is a problem, a depot medication may help to keep the patient free of psychotic symptoms. Frequently used depot antipsy-chotics are haloperidol-decanoate, fluphenazine-decanoate, and fluspirilene, which are given in relatively low dosages (see Table 41.4). In EOS, relapse prevention is more important than in adulthood, as the majority of patients have not yet finished school or started a professional career. 

Using meta-analytic techniques based on the means and the standard errors presented graphically in the poster, we estimated pooled data of the four effective dosages of quetiapine both for the BPRS and the CGI severity of illness change scores from baseline to endpoint. Quetiapine produced an improvement of 0.43 effect-size units in comparison with placebo, a difference that was highly statistically significant and about the same improvement as haloperidol. Thus, based on the BPRS or PANSS, quetiapine was similar to neuroleptics in efficacy (i.e., differences were nonsignificant). Based on our meta-analysis, quetiapine is clearly superior to... 

Clinically, haloperidol decanoate has been administered to hundreds of chronic schizophrenic patients in several open studies to determine its efficacy, pharmacokinetics, safety, and adverse effects. The trials ranged from 4 months to 2 years, with dosages ranging from 25 to 500 mg given once every 4 weeks. The results of these studies have consistently shown that depot haloperidol ... 

Nair NPV, Suranyi-Cadotte B, Schwartz G, et al. A clinical trial comparing intramuscular haloperidol decanoate and oral haloperidol in chronic schizophrenic patients efficacy, safety, and dosage equivalence. J Clin Psychopharmacol 1986 6(suppl 1) 30S-37S. 

Deberdt R, Elens P, Berghmans W, et al. Intramuscular haloperidol decanoate for neuroleptic maintenance therapy. Efficacy, dosage schedule and plasma levels. An open multicenter study. 

Kane JM. Dosage strategies with long-acting injectable neuroleptics, including haloperidol decanoate. J Clin Psychopharmacol 1986 6(suppl) 20S-23S. 

Kissling W, Moller HJ, Walter K, et al. Double-blind comparison of haloperidol decanoate and fluphenazine decanoate effectiveness, adverse effects, dosage and serum levels during a six months treatment for relapse prevention. Pharmacopsychiatry 1985 18 240-245. 

The pharmacologic basis of these disorders is unknown, and there is no satisfactory medical treatment for them. A subset of patients respond well to levodopa medication (dopa-responsive dystonia), which is therefore worthy of trial. Occasional patients with dystonia may respond to diazepam, amantadine, antimuscarinic drugs (in high dosage), carbamazepine, baclofen, haloperidol, or phenothiazines. A trial of these pharmacologic approaches is worthwhile, though often not successful. Patients with focal dystonias such as blepharospasm or torticollis often benefit from injection of botulinum toxin into the overactive muscles. The role of deep brain stimulation for the treatment of these conditions is being explored. 

---