Olanzapine and fluoxetine

Uses

Fluoxetine is used for-

• Depressive illness
• Bulimia nervosa and anorexia nervosa
• Obsessive compulsive disorders
• Pre-menstrual syndrome

Olanzapine is used for the acute and maintenance treatment of schizophrenia and related psychoses where positive symptoms (e.g. delusions, hallucinations, disordered thinking, hostility and suspiciousness) and/or negative symptoms (e.g. flattened affect, emotional and social withdrawal, poverty of speech) are prominent.

Olanzapine is used for the treatment of acute manic or mixed episodes in bipolar disorder, with or without psychotic features and with or without a rapid cycling course

Olanzapine and fluoxetine is also used to associated treatment for these conditions: Alcohol Dependency, Anorexia Nervosa (AN), BMI >30 kg/m2, Bulimia Nervosa, Cataplexy, Depression, Bipolar, Major Depressive Disorder (MDD), Myoclonus, Obsessive Compulsive Disorder (OCD), Panic Disorder (With or Without Agoraphobia), Premature Ejaculation, Premenstrual Dysphoric Disorder, Treatment Resistant Depression (TRD)Acute Agitation, Acute Depressive Episode, Bipolar 1 Disorder, Bipolar Disorder With Manic or Mixed Episodes, Delirium, Delusional Parasitosis, Gilles de la Tourette's Syndrome, Major depressive disorder, recurrent episode, Mixed manic depressive episode, Post Traumatic Stress Disorder (PTSD), Psychosis, Schizophrenia, Acute Manic episode

How Olanzapine and fluoxetine works

The monoaminergic hypothesis of depression emerged in 1965 and linked depression with dysfunction of neurotransmitters such as noradrenaline and serotonin. Indeed, low levels of serotonin have been observed in the cerebrospinal fluid of patients diagnosed with depression. As a result of this hypothesis, drugs that modulate levels of serotonin such as fluoxetine were developed.

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) and as the name suggests, it exerts it's therapeutic effect by inhibiting the presynaptic reuptake of the neurotransmitter serotonin. As a result, levels of 5-hydroxytryptamine (5-HT) are increased in various parts of the brain. Further, fluoxetine has high affinity for 5-HT transporters, weak affinity for noradrenaline transporters and no affinity for dopamine transporters indicating that it is 5-HT selective.

Fluoxetine interacts to a degree with the 5-HT_2C receptor and it has been suggested that through this mechanism, it is able to increase noradrenaline and dopamine levels in the prefrontal cortex.

The activity of olanzapine is achieved by the antagonism of multiple neuronal receptors including the dopamine receptor D1, D2, D3 and D4 in the brain, the serotonin receptors 5HT2A, 5HT2C, 5HT3 and 5HT6, the alpha-1 adrenergic receptor, the histamine receptor H1 and multiple muscarinic receptors.

As abovementioned, olanzapine presents a wide profile of targets, however, its antagonistic effect towards the dopamine D2 receptor in the mesolimbic pathway is key as it blocks dopamine from having a potential action at the post-synaptic receptor. The binding of olanzapine to the dopamine D2 receptors is easily dissociable and hence, it allows for a certain degree of dopamine neurotransmission.

On the other hand, olanzapine acts in the serotonin 5HT2A receptors in the frontal cortex in a similar manner than the reported on dopamine D2 receptors. This determined effect allows for a decrease in adverse effects.

Dosage

Olanzapine and fluoxetine dosage

Initial treatment: Recent studies suggest that 20 mg/day of Fluoxetine may be sufficient to obtain satisfactory antidepressant response. Consequently, a dose of 20 mg/day administered in the morning is recommended as the initial dose.

A dose increase may be considered after several weeks if no clinical improvement is observed. Dosage above 20 mg/day, should be administered on a bid schedule (i.e. morning and noon) and should not exceed a maximum dose of 80 mg/day. As with other antidepressants, the full antidepressant effect may be delayed until 4 weeks of treatment or longer. As with many other medications, a lower or less frequent dosage should be used in patients with renal and/or hepatic impairment.

A lower or less frequent dosage should also be considered for patients, such as elderly, with concurrent disease or on multiple medication. A recommended maximum dose for elderly patients is 60 mg per day.

Maintenance treatment: It is generally agreed among expert psychopharmacologists that acute episode of depression requires several months or longer sustained pharmacologic therapy. Fluoxetine is also used in dosage of 60 mg daily for the management of bulimia nervosa.

The recommended starting dose for Olanzapineis 10 mg/day, administered as a single daily dose without regard to meals. Daily dosage may subsequently be adjusted on the basis of individual clinical status within the range of 5-20 mg daily. An increase to a dose greater than the routine therapeutic dose of 10 mg/day i.e. to a dose of 15 mg/day or greater, is recommended only after appropriate clinical reassessment.

Children: Olanzapine has not been studied in subjects under 18 years of age.

Elderly patients (age 65 and over): starting dose 5 mg/day

Patients with hepatic and/or renal impairment: starting dose 5 mg/day

When more than one factor is present which might result in slowermetabolism (female gender, geriatric age, non-smoking status), consideration should be given to decreasing the starting dose. Dose escalation, when indicated, should be conservative in such patients.

Side Effects

Gastrointestinal: Nausea, vomiting, dyspepsia, dry mouth, and diarrhoea.

Neurological: Anxiety, nervousness, insomnia/ drowsiness and fatigue.

Others: Excessive sweating, pruritus, skin rashes associated with liver, kidney and lung involvement. It has therefore been advised that Fluoxetine therapy should be discontinued in any patient who develops a skin rash.

Very common undesirable effects are somnolence and weight gain. Besides increased appetite, elevated glucose levels, elevated triglyceride levels, dizziness, akathisia, Parkinson's disease, dyskinesia, orthostatic hypotension, mild and transient anticholinergic effects including constipation and dry mouth, asthenia, edema and photosensitivity reaction etc. may be observed.

Toxicity

In a report that included 234 fluoxetine overdose cases, it was concluded that symptoms resulting from fluoxetine overdose were generally minor and short in duration. The most common overdose adverse effects included drowsiness, tremor, tachycardia, nausea and vomiting, and providing the patient with aggressive supportive care was the recommended intervention.

Despite this evidence, more severe adverse effects have been linked to fluoxetine ingestion although most of these reports involved co-ingestion with other substances or drugs as well as other factors. For example, there is a case report that details a patient who ingested 1400 mg of fluoxetine in a suicide attempt and as a result, experienced a generalized seizure three hours later. In a separate case, a 14 year old patient ingested 1.2 g of fluoxetine and subsequently experienced tonic/clonic seizures, symptoms consistent with serotonin syndrome, and rhabdomyolysis, although the patient did not experience sustained renal injury.

The toxicity symptoms of olanzapine are known to include somnolence, mydriasis, blurred vision, respiratory depression, hypotension, extrapyramidal symptoms and anticholinergic effects. The overdosage effects in children are generally associated with more significant side effects.

The maximum registered dosage of olanzapine in clinical trials was of 300 mg and it was reported to present drowsiness and slurred speech. However, on post-marketing surveillance, a wide range of symptoms have been presented including agitation, dysarthria, tachycardia, extrapyramidal symptoms, and reduced consciousness. One case of overdosage-driven death was reported after ingestion of 450 mg of olanzapine. In the cases of acute overdosage, the establishment of adequate oxygenation and ventilation, gastric lavage and administration of activated charcoal with a laxative is recommended.

In carcinogenesis studies, olanzapine was showed to present an increase in the incidence of liver hemangiomas and hemangiosarcomas as well as mammary gland adenomas, and adenocarcinomas. On fertility studies, there was solely found impairment in male mating performance and delays in ovulation. There is no evidence of mutagenic, genotoxic potential not adverse events on fertility.

Precaution

As Fluoxetine undergoes hepatic metabolism and renal excretion, it should be used with caution and in reduced doses in patients with impaired hepatic or renal function. Because of its epileptogenic effect, it should be used with caution in patients with epilepsy or a history of such disorders. Fluoxetine may alter glycaemic control and therefore caution is also warranted in diabetic subjects. Depressed patients with suicidal tendencies should be carefully supervised during treatment. Fluoxetine is not usually considered a suitable form of therapy for the depressive component of bipolar (manic depressive) illness as mania may be precipitated.

Olanzapine should be used cautiously in patients who have a history of seizures or have conditions associated with seizures. Olanzapine should be used cautiously in patients with low leukocyte and/or neutrophil counts for any reason, drug induced bone marrow depression/toxicity caused by radiation therapy or chemotherapy, hypereosinophilic conditions, impaired hepatic function, and patients using hepatotoxic medicines, centrally acting drug and medicines know to increase QT interval, especially in the elderly. Patients should be cautioned about operating hazardous machinery, including motor vehicles.

Interaction

May lead to serotonin syndrome with serotonergic drugs (e.g. triptans, TCAs, fentanyl, tramadol, lithium, buspirone, tryptophan). May increase risk of bleeding with aspirin, NSAIDs, warfarin and other anticoagulants. May increase plasma levels of phenytoin.

Potentially Fatal: May increase risk of serotonin syndrome with concomitant admin or within 14 days of MAOIs withdrawal. May increase the QTc prolonging effect of pimozide and thioridazine.

Drugs that induce CYP1A2 or glucoronyl transferase enzymes (omeprazole, rifampicin), inhibitor of CYP1A2 (fluvoxamine), centrally acting drugs, antihypertensive agents.

Volume of Distribution

The volume of distribution of fluoxetine and it's metabolite varies between 20 to 42 L/kg.

The volume of distribution of olanzapine is reported to be of 1000 liters which indicate a large distribution throughout the body.

Elimination Route

The oral bioavailability of fluoxetine is 13

In a bioequivalence study, the Cmax of fluoxetine 20 mg for the established reference formulation was 11.754 ng/mL while the Cmax for the proposed generic formulation was 11.786 ng/ml.

Fluoxetine is very lipophilic and highly plasma protein bound, allowing the drug and it's active metabolite, norfluoxetine, to be distributed to the brain.

Olanzapine presents a linear pharmacokinetic profile and, after daily administration, it reaches steady-state in about a week. Under the administration of a normal dosage of olanzapine, the steady-state plasma concentration does not seem to exceed 150 ng/ml with an AUC of 333 ng/h/ml.

The absorption of olanzapine is not affected by the concomitant administration of food. The pharmacokinetic profile of olanzapine is characterized by reaching peak plasma concentration of 156.9 ng/ml approximately 6 hours after oral administration.

Half Life

The half life of fluoxetine is significant with the elimination half-life of the parent drug averaging 1-3 days after acute administration, and 4-6 days after chronic administration. Further, the elimination half life of it's active metabolite, norfluoxetine, ranges from 4-16 days after both acute and chronic administration. The half-life of fluoxetine should be considered when switching patients from fluoxetine to another antidepressant since marked accumulation occurs after chronic use. Fluoxetine's long half-life may even be beneficial when discontinuing the drug since the risk of withdrawal is minimized.

Olanzapine presents a half-life ranging between 21 to 54 hours with an average half-life of 30 hours.

Clearance

The clearance value of fluoxetine in healthy patients is reported to be 9.6 ml/min/kg.

The mean clearance rate of olanzapine is of 29.4 L/hour however, some studies have reported an apparent clearance of 25 L/h.

Elimination Route

Fluoxetine is primarily eliminated in the urine.

Olanzapine is mainly eliminated through metabolism and hence, only 7% of the eliminated drug can be found as the unchanged form. It is mainly excreted in the urine which represents around 53% of the excreted dose followed by the feces that represent about 30%.

Pregnancy & Breastfeeding use

Pregnancy: In animal studies, no teratogenicity or harmful effect was found. Because animal reproductive studies are not always predictive of human responses, Fluoxetine should be used in pregnancy only if clearly needed.

Lactation: As Fluoxetine is excreted in human milk, caution should be exercised when Fluoxetine is administered to nursing women.

Olanzapine should be used in pregnancy only if the potential benefits justify the potential risk to the foetus. So, patients should be advised to notify their physician if they become pregnant or intend to become pregnant during treatment with Olanzapine. There is no report to show teratogenecity. Patients should not breast feed if they are taking Olanzapine.

Contraindication

Fluoxetine Hydrochloride is contraindicated in patients known to be hypersensitive to it.

Monoamine oxidase inhibitors: There have been reports of serious, sometimes fatal reactions (including hyperthermia, rigidity, myoclonus, autonomic instability with possible rapid fluctuations of vital signs and changes of mental status that include extreme agitation progressing to delirium and coma) in patients receiving Fluoxetine in combination with monoamine oxidase inhibitors (MAOIs), and in patients who have recently discontinued Fluoxetine and are then started on MAOIs. Some cases presented with features resembling neuroleptic malignant syndrome. Therefore, Fluoxetine should not be used in combination with MAOI, or within 14 days of discontinuing therapy with MAOI. Since Fluoxetine and its major metabolites have very long elimination half-lives, at least 5 weeks should be allowed after stopping Fluoxetine and before starting MAOI.

This is contraindicated in those patients with a known hypersensitivity to Olanzapine as well as in patients with known risk for narrow-angle glaucoma.

Concomitant illness: Olanzapine in patients with concomitant illness is limited, caution is advised when prescribing for patients with prostatic hypertrophy, or paralytic ileus and related conditions.

Neuroleptic Malignant Syndrome (NMS): If a patient develops signs and symptoms indicative of NMS, or presents with unexplained high fever without additional clinical manifestations of NMS, all antipsychotic medicines, including olanzapine must be discontinued.

Special Warning

Use in children: The use of Fluoxetine in children is not recommended as safety and efficacy have not been established.

Acute Overdose

Symptoms: Nausea, vomiting, seizure, CV dysfunction ranging from asymptomatic arrhythmias to cardiac arrest (including ventricular arrhythmias and nodal rhythm) or ECG changes indicative of QTc prolongation to cardiac arrest, pulmonary dysfunction, signs of altered CNS status ranging from excitation to coma.

Management: Symptomatic and supportive treatment. May admin activated charcoal w/ sorbitol.

Symptoms: Tachycardia, agitation/aggressiveness, dysarthria, extrapyramidal symptoms, reduced level of consciousness ranging from sedation to coma.

Management: Symptomatic and supportive treatment. Gastric lavage and admin of activated charcoal may be effective.

Storage Condition

Store between 20-25° C. Protect from light.

Store below 30˚ C. Protect from light and moisture. Keep out of the reach of children.

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