Contraindicated combinations (see section 4.3)
Citalopram, escitalopram, hydroxyzine, piperaquine, domperidone
Increased risk of ventricular rhythm disorders, particularly torsades de pointes.
Combinations not recommended (see section 4.4)
Adrenaline
Adrenaline (epinephrine) must not be used in patients overdosed with neuroleptics (see section 4.9).
Dopaminergics
Mutual antagonism between dopaminergics and neuroleptics. Dopaminergics may cause or exacerbate psychotic disorders. If treatment with neuroleptics is required in patients with Parkinson's disease treated with dopaminergic, the latter should be tapered off gradually (sudden discontinuation of dopaminergic agents exposes the patient to a risk of “neuroleptic malignant syndrome”).
Levodopa
Reciprocal antagonism of the levodopa and the neuroleptics. In Parkinson's disease, use the minimum effective dose of each of the two medicinal products.
Medicinal products likely to cause torsades de pointes
• class IA antiarrhythmics (e.g. quinidine, hydroquinidine, disopyramide, procainamide)
• class III antiarrhythmics (e.g. amiodarone, dronedarone, sotalol, bretylium and dofetilide)
• certain antimicrobials (such as sparfloxacin, moxifloxacin, IV spiramycin and IV erythromycin) and anti-parasitics (chloroquine, halofantrine, lumefantrine, pentamidine, quinine and mefloquine)
• tricyclic antidepressants (e.g. amitriptyline)
• tetracyclic antidepressants (e.g. maprotiline)
• other neuroleptics (e.g. phenothiazines, pimozide and sertindole)
• antihistamines (e.g. terfenadine, mizolastine, mequitazine)
• other medicinal products such as arsenic trioxide, diphemanil, cisapride, IV dolasetron, prucalopride, toremifene, vandetanib, IV vincamine, methadone, hydroxychloroquine
Increased risk of arrhythmias when antipsychotics are used with concomitant QT prolonging drugs (including certain antiarrhythmics, antidepressants and other antipsychotics) and drugs causing electrolyte imbalance. If possible, one of the two treatments should be discontinued. If the combination cannot be avoided, the QT interval should be checked before treatment and the ECG monitored (see section 4.4).
Combinations which should be used with caution
Beta blockers for heart failure (bisoprolol, carvedilol, metoprolol, nebivolol)
Increased risk of ventricular rhythm disorders, particularly torsades de pointes. Vasodilator effect and risk of hypotension, particularly in orthostatic hypotension (additive effect). Clinical and ECG monitoring is required.
Hypokalaemia-inducing medicinal products (potassium-depleting diuretics alone or in combination, stimulant laxatives, glucocorticoids, tetracosactide and intravenous amphotericin B)
Diuretics, in particular those causing hypokalaemia, should be avoided but, if necessary, potassium-sparing diuretics are preferred. Hypokalaemia should be corrected before administering the medicinal product and clinical, electrolyte, and ECG monitoring should be carried out.
Medicinal products which lower the seizure threshold
The combined use of medicinal products which are pro-convulsant, or which lower the seizure threshold, should be carefully assessed due to the seriousness of the risk incurred. The main examples of such medicinal products are most of the antidepressants (imipramine-like, selective serotonin reuptake inhibitors), the neuroleptics (phenothiazines, butyrophenones), mefloquine, chloroquine, bupropion and tramadol.
Cytochrome P450 2D6 Metabolism
There is a possible pharmacokinetic interaction between inhibitors of CYP2D6, such as phenothiazines and CYP2D6 substrates (mainly nortriptyline).
Levomepromazine and its non-hydroxylated metabolites are reported to be potent inhibitors of cytochrome P450 2D6 (CYP2D6). Co-administration of levomepromazine and drugs primarily metabolised by the CYP2D6 enzyme system may result in increased plasma concentrations of these drugs. Monitor patients for dose-dependent adverse reactions associated with CYP2D6 substrates such as amitriptyline/amitriptylinoxide.
Desferrioxamine
Simultaneous administration of desferrioxamine and prochlorperazine has been observed to induce a transient metabolic encephalopathy, characterised by loss of consciousness for 48 – 72 hours. It is possible that this may occur with Nozinan, since it shares many of the pharmacological activities of prochlorperazine.
Combinations to be considered
Atropine-like medicinal products
The fact that the undesirable effects of atropine-like substances may be additive and more easily lead to urinary retention, an acute flare-up of glaucoma, constipation, dry mouth etc., must be considered.
Examples of atropine-like medicinal products are imipramine-like antidepressants, most atropine-like H1 antihistamines, anticholinergic antiparkinsonian agents, atropine-like antispasmodics, disopyramide, phenothiazine neuroleptics and clozapine.
Dapoxetine
Risk of increased undesirable effects, particularly vertigo and syncope.
Medicinal products which lower blood pressure
Increased risk of hypotension, particularly orthostatic hypotension. As well as the antihypertensives, many medicinal products may lead to orthostatic hypotension. This is particularly the case of nitrate derivatives, phosphodiesterase type-5 inhibitors, alpha-blockers for urological purposes, imipramine antidepressants and neuroleptic phenothiazines, dopaminergic agonists, and levodopa. Using them in combination therefore risks increasing the frequency and intensity of this undesirable effect.
Guanethidine
Inhibition of the antihypertensive effect of guanethidine (inhibition of guanethidine uptake into sympathetic fibre, its site of action).
Orlistat
Risk of therapeutic failure in the case of concomitant treatment with orlistat.
Lithium
Risk of onset of neuropsychiatric symptoms suggestive of a neuroleptic malignant syndrome or of lithium poisoning.
Sedative medicinal products and barbiturates
Increased CNS depression. Decreased alertness may make driving vehicles and using machines dangerous.
Alcohol (beverage or excipient)
Alcohol increases the sedative effect of these substances. Respiratory depression may occur. Decreased alertness may make driving vehicles and using machines dangerous. Avoid the consumption of alcoholic beverages and other medicinal products containing alcohol.