5-HT1A Receptor; 5-HT2A Receptor; 5-HT2B Receptor; 5-HT2C Receptor; D2 Receptor; D3 Receptor; D4 Receptor
This study focuses on the bioconversion of the prodrug, not its pharmacological target. The active moiety, aripiprazole, is a partial agonist at dopamine D₂ receptors and serotonin 5-HT₁A receptors, and an antagonist at 5-HT₂A receptors. [1]

Aripiprazole lauroxil is a dodecanoate ester obtained by formal condensation of the carboxy group of dodecanoic acid with the hydroxy group of 7-{4-[4-(2,3-dichlorophenyl)piperazin-1-yl]butoxy}-2-oxo-3,4-dihydroquinolin-1(2H)-yl]methanol. A prodrug for aripiprazole, it is used for treatment of schizophrenia. It has a role as a H1-receptor antagonist, a second generation antipsychotic, a serotonergic agonist and a prodrug. It is a dodecanoate ester, a quinolone, a dichlorobenzene, a N-arylpiperazine, a N-alkylpiperazine, an aromatic ether and a delta-lactam. [1]

---

The bioconversion of aripiprazole lauroxil was investigated in rat plasma at 37°C. When the prodrug was added to plasma, the expected intermediate, N-hydroxymethyl aripiprazole, was readily observed in samples taken at 0.5 and 1 hour post-spike, as confirmed by mass chromatograms. This demonstrates the two-step conversion process via the intermediate. [1]
- In a separate experiment to study the second step of the conversion, N-hydroxymethyl aripiprazole was added to phosphate buffer (pH 7.4). Its conversion to aripiprazole was monitored by ¹H NMR. At 25°C, the apparent first-order rate constant was 0.0044 min⁻¹ with a half-life of approximately 35 minutes. At 37°C, the conversion was too fast to measure precisely, with more than half converted within the first 15 minutes. [1]

The intermediate N-corresponding aripiprazole is involved in the in vivo biotransformation of aripiprazole lauroxil (in-vehicle product; 1.87 mg/mL). Thus, Aripiprazole lauroxil has a high rate of biotransformation, resulting in the synthesis of the observed N-corresponding methyl aripiprazole, according to peripheral data. When animals are given Aristrozole Lauroyl, the concentrations of Aristrozole are very high [1].

---

The pharmacokinetics and bioconversion of aripiprazole lauroxil were studied in female Sprague-Dawley rats following a single intravenous dose (5 mg/kg aripiprazole equivalent) formulated as a sub-micron emulsion. The study confirmed the two-step bioconversion pathway in vivo, as all three compounds (the prodrug, the N-hydroxymethyl intermediate, and the parent aripiprazole) were detected in plasma. [1]
- After administration of aripiprazole lauroxil, the clearance was 0.32 ± 0.11 L/h/kg. Notably, the concentration of the N-hydroxymethyl aripiprazole intermediate observed in vivo was surprisingly high, suggesting its accumulation during bioconversion. [1]

In vitro conversion in buffer[2]
To follow the spontaneous conversion from N-hydroxymethyl aripiprazole/aripiprazole lauroxil to aripiprazole, a stock solution in DMSO-d6 was made so the reaction could be started by adding the stock solution into a phosphate buffer, pH 7.4, which thereby contained 0.5% v/v DMSO-d6. The final concentration of N-hydroxymethyl aripiprazole/aripiprazole lauroxil in the buffer was 9 µM equal to the solubility of aripiprazole in water. The degradation was followed at both 25 °C and 37 °C by continuous measurements.[2]
1H NMR spectra were measured at 600.163 MHz on a Bruker AV-III-600 equipped with a 5 mm TCI CryoProbe. Referencing was done to DMSO-d6 (2.51 ppm). Solvent suppression with excitation sculpting using a square 180 pulse of 4 ms was applied on aqueous solutions. Acquisition time was 1.7 s and repetition delay was 3 s A Lorentzian Line broadening of 1.0 Hz was applied before FT, and the aromatic region was baseline corrected manually using a 4th degree polynomial fit before integration.

---

In vitro conversion in plasma[2]
An in vitro experiment was conducted in triplicate by adding 30 µL 1 µM aripiprazole lauroxil dissolved in ethanol to 1.47 mL rat plasma from female Sprague Dawley rats at 37 °C. The spiked plasma was stored at 37 °C and 50 µL aliquots were taken at 0.5 and 1.0 h post-spike. The aliquots were immediately treated with 200 µL cold acetonitrile containing 0.4% citric acid and stored at -80 °C until analysed as described in Section 2.7.

---

Animal/Disease Models: Female SD (SD (Sprague-Dawley)) rats[1]
Doses: 1.87 mg/ml
Route of Administration: Blood samples were collected at 5, 15, 30 minutes and 1, 2, 4, 6, 8 and 24 hrs (hrs (hours)) after administration.
Experimental Results: Displayed clearance: 0.32 ± 0.11 L/h/kg.

---

Formulations for the in vivo study [2]
An emulsion for intravenous administration containing each of the three compounds (i.e., aripiprazole, N-hydroxymethyl-aripiprazole or aripiprazole lauroxil) in equimolar concentrations equivalent to 1 mg aripiprazole was produced. The emulsions consisted of compound, 20% w/w fractionated coconut oil, 1.2% w/w lecithin, 2% w/w glycerol and q.s. water. The amount of each compound added was 1 mg aripiprazole/mL, 1.2 mg N-hydroxymethyl-aripiprazole/mL or 1.87 mg aripiprazole lauroxil/mL, i.e., equimolar. Each of the three compounds was dissolved in the oil together with lecithin and gently heated to 50 °C with continuous stirring. Glycerol was added to the aqueous phase as an isotonic agent and the aqueous phase was heated to 50 °C. The two phases were mixed and homogenised to a pre-emulsion by rapid stirring for 1 min. The pre-emulsion was placed on ice and the droplet size was further reduced by means of a homogeniser equipped with a standard microtip at a power output of 5 (Sonifier Cell Disruptor, Model B15, Branson, Pusan, Korea) for 10 min. The formulation was then filtered through a 0.45 µm sterile filter into a sterilised glass bottle with a rubber membrane and a crimped lid.

---

In vivo study[2]
The protocol used for the in vivo study in rats was approved by the institutional animal ethics committee in accordance with Danish law regulating experiments on animals and in compliance with EC directive 2010/63/EU, and the NIH guidelines on animal welfare. Female Sprague Dawley rats, weighing 248–276 g on the day of administration, were used for the pharmacokinetic studies (n = 6 per group). The animals were acclimatised for a minimum of 5 days in groups of 2 on wooden bedding in plastic cages, 595 × 380 × 200 mm3, with a stainless steel lid in humidity- and temperature-controlled ventilation cupboards, relative humidity 40–60%, temperature 20 ± 1 °C, light from 6:00–18:00 h. The animals had free access to a standard rodent diet and water ad libitum during the study.[2]
The animals were randomly assigned to three groups (n = 6 per group) receiving either aripiprazole, N-hydroxymethyl-aripiprazole or aripiprazole lauroxil molar equivalent to 5 mg aripiprazole/kg. The animals were dosed by injection into the tail vein with a submicron emulsion containing a molar concentration equivalent to 1 mg aripiprazole/mL. Blood samples of 100 µL were obtained from the lateral tail vein by individual vein puncture and collected into potassium–EDTA tubes. Samples was taken at 5, 15, 30 min and 1, 2, 4, 6, 8 and 24 h after administration. Plasma was harvested immediately by 10 min of centrifugation at 4 °C, 2765g and stored at -80 °C until analysed. At the end of the experiment, the animals were sacrificed.

---

---

Animals:** Female Sprague-Dawley rats (248-276 g) were used. They were acclimatized for at least 5 days in a controlled environment (temperature 20±1°C, relative humidity 40-60%, 12-hour light/dark cycle) with free access to food and water. [1]
- **Formulation Preparation (Intravenous Emulsion):** An equimolar dose equivalent to 1 mg aripiprazole/mL was formulated for each compound. The emulsion consisted of 20% w/w fractionated coconut oil, 1.2% w/w lecithin, 2% w/w glycerol, and water. The test compound was dissolved in the oil phase with gentle heating (50°C) and stirring. The aqueous phase (with glycerol) was heated to 50°C. The phases were mixed and homogenized to form a pre-emulsion, which was then placed on ice and further homogenized for 10 minutes using a sonicator to reduce droplet size. The final formulation was filtered through a 0.45 μm sterile filter. [1]
- **Dosing and Sampling:** Rats (n=6 per group) were randomly assigned to receive aripiprazole, N-hydroxymethyl aripiprazole, or aripiprazole lauroxil at a molar equivalent dose of 5 mg aripiprazole/kg via tail vein injection. Blood samples (100 μL) were collected from the lateral tail vein at 5, 15, 30 minutes and 1, 2, 4, 6, 8, and 24 hours post-dose into EDTA tubes. Plasma was harvested by centrifugation and stored at -80°C until analysis. [1]

---

Animals: Female Sprague-Dawley rats (248-276 g) were used. They were acclimatized for at least 5 days in a controlled environment (temperature 20±1°C, relative humidity 40-60%, 12-hour light/dark cycle) with free access to food and water. [1]
- Formulation Preparation (Intravenous Emulsion): An equimolar dose equivalent to 1 mg aripiprazole/mL was formulated for each compound. The emulsion consisted of 20% w/w fractionated coconut oil, 1.2% w/w lecithin, 2% w/w glycerol, and water. The test compound was dissolved in the oil phase with gentle heating (50°C) and stirring. The aqueous phase (with glycerol) was heated to 50°C. The phases were mixed and homogenized to form a pre-emulsion, which was then placed on ice and further homogenized for 10 minutes using a sonicator to reduce droplet size. The final formulation was filtered through a 0.45 μm sterile filter. [1]
- Dosing and Sampling: Rats (n=6 per group) were randomly assigned to receive aripiprazole, N-hydroxymethyl aripiprazole, or aripiprazole lauroxil at a molar equivalent dose of 5 mg aripiprazole/kg via tail vein injection. Blood samples (100 μL) were collected from the lateral tail vein at 5, 15, 30 minutes and 1, 2, 4, 6, 8, and 24 hours post-dose into EDTA tubes. Plasma was harvested by centrifugation and stored at -80°C until analysis. [1]

Absorption, Distribution and Excretion
Following a single intramuscular injection of sustained-release aripiprazole, aripiprazole is detectable in systemic circulation within 5 to 6 days and continues to be released for 36 days. Aripiprazole concentrations increase with repeated administration of aripiprazole and reach steady state after the fourth monthly injection. Systemic exposure is similar after intramuscular injection of aripiprazole into the deltoid and gluteal muscles. According to pharmacokinetic studies of aripiprazole, less than 1% of the unchanged aripiprazole is excreted in the urine, and approximately 18% of the oral dose is excreted unchanged in the feces. Based on population pharmacokinetic analysis, the apparent volume of distribution of aripiprazole after intramuscular injection is 268 L, indicating extensive extravascular distribution after absorption. Studies in healthy volunteers have shown that aripiprazole can cross the blood-brain barrier. In rats, the clearance of aripiprazole was 0.32 ± 0.11 L/h/kg after injection of aripiprazole equivalent to 5 mg/kg aripiprazole. Metabolites/Metabolites Aripiprazole is hydrolyzed by esterases to N-hydroxymethylaripiprazole. N-hydroxymethylaripiprazole undergoes rapid non-enzymatic spontaneous cleavage or water-mediated hydrolysis to produce aripiprazole, which is the main source of the pharmacological action of aripiprazole. Aripiprazole is further metabolized in the liver by CYP3A4 and CYP2D6 to dehydroaripiprazole, which retains some pharmacological activity. Dehydroaripiprazole has a similar affinity for the D2 receptor to aripiprazole and accounts for 30-40% of aripiprazole exposure in plasma. Genetic polymorphism in cytochrome P450 2D6 leads to pharmacokinetic differences between CYP2D6 metabolic phenotypes, thus requiring appropriate dose adjustments.

---

Biological Half-Life
After injection of aripiprazole loloxi 441, 662 and 882 mg every 4 weeks, the mean terminal elimination half-life of aripiprazole ranged from 29.2 days to 34.9 days.

---

Aripiprazole lauroxil is an N-acycloxymethyl prodrug of aripiprazole. Its bioconversion to the active parent drug, aripiprazole, is a two-step process: first, enzymatic hydrolysis of the ester bond to yield the N-hydroxymethyl intermediate and lauric acid; second, spontaneous, non-enzymatic cleavage of the N-hydroxymethyl intermediate to release aripiprazole and formaldehyde. [1]
- After intravenous administration to rats, the clearance (CL) of aripiprazole lauroxil was 0.32 ± 0.11 L/h/kg. [1]
- The study confirmed that the intermediate, N-hydroxymethyl aripiprazole, is present in the systemic circulation at levels comparable to the parent drug aripiprazole after prodrug administration. [1]

Protein Binding

Aripiprazole and its main metabolites have a serum protein binding rate of >99% at therapeutic concentrations, primarily binding to albumin.

---

The study does not present direct toxicity data for aripiprazole lauroxil. However, it highlights potential toxicological concerns associated with its bioconversion: (1) the formation of the N-hydroxymethyl aripiprazole intermediate, whose pharmacological and toxicological profile needs to be evaluated, and (2) the release of formaldehyde during the final conversion step. [1]

[1]. Long-Acting Injectable Second-Generation Antipsychotics: An Update and Comparison Between Agents.CNS Drugs. 2018 Mar;32(3):241-257.

[2]. Biological conversion of aripiprazole lauroxil - An N-acyloxymethyl aripiprazole prodrug.Results Pharma Sci. 2014 May 2;4:19-25.

Aripiprazole lorazepam is a dodecanoate ester, formed by the condensation of the carboxyl group of dodecanoic acid with the hydroxyl group of 7-{4-[4-(2,3-dichlorophenyl)piperazin-1-yl]butoxy}-2-oxo-3,4-dihydroquinoline-1(2H)-yl]methanol. It is a prodrug of aripiprazole used to treat schizophrenia. It has multiple functions, including H1 receptor antagonist, second-generation antipsychotic, serotonergic agonist, and prodrug action. It is a dodecanoate ester, quinolone, dichlorobenzene, N-arylpiperazine, N-alkylpiperazine, aromatic ether, and δ-lactam compound. Aripiprazole lorazepam is a long-acting injectable atypical antipsychotic used to treat schizophrenia in adults. It is a prodrug of aripiprazole, which acts as a partial agonist of D2 and 5-HT1A receptors and an antagonist of 5-HT2A receptors. Schizophrenia affects approximately 1% of the adult population in the United States and about 26 million people worldwide. It is a chronic neurological disorder that can lead to cognitive and executive dysfunction. Due to adverse health consequences, patients experience significantly reduced quality of life and often face social stigma and discrimination. Schizophrenia is characterized by positive symptoms (such as delusions, hallucinations, thought disorders, and catatonia) and negative symptoms (including social withdrawal, anhedonia, and emotional blunting). D2 receptors are the most commonly used target for antipsychotic drugs treating schizophrenia: positive symptoms are thought to be caused by overactive dopaminergic pathways in the mesolimbic system activating D2 receptors, while negative symptoms may be caused by reduced activity in the mesocortical dopaminergic pathways (primarily D1 receptors). In a randomized, double-blind clinical trial, aripiprazole and lorazepam were used to treat adult patients with schizophrenia, resulting in improvements in both positive and negative symptom scores by day 85 of treatment. Aripiprazole and lorazepam was initially approved by the U.S. Food and Drug Administration (FDA) in October 2015 under the brand name Aristada for the treatment of schizophrenia. This drug is administered via intramuscular injection. For treatment-naïve patients, tolerability should be assessed before administration. On July 2nd, the FDA approved another aripiprazole lorazepam formulation, marketed as Aristada Initio, which can be used to immediately initiate Aristada treatment at any dose. Patients can take Aristada Initio concurrently with a single oral 30 mg dose of aripiprazole to achieve appropriate aripiprazole plasma concentrations more quickly. Long-acting injectable aripiprazole lorazepam has similar efficacy and safety to aripiprazole, but with a reduced dosing frequency, improving patient adherence.
See also: Aripiprazole (containing the active ingredient).
Drug Indications

Aripiprazole lorazepam is indicated for the treatment of schizophrenia and related psychotic disorders.
FDA Label
Mechanism of Action

The pharmacological activity of aripiprazole lorazepam is primarily mediated by its metabolite aripiprazole, followed by dehydroaripiprazole. Aripiprazole acts as a partial agonist of dopamine D2 receptors and serotonin 5-HT1A receptors, and an antagonist of serotonin 5-HT2A receptors. The expected outcome of antipsychotic drug treatment for schizophrenia is the inhibition of dopaminergic transmission in the limbic system and the enhancement of dopaminergic transmission in the prefrontal cortex. Aripiprazole, as a partial agonist of D2 receptors in the mesolimbic dopamine pathway, acts as a functional antagonist in the mesolimbic dopamine pathway, reducing the activity of the dopaminergic pathway. This leads to a reduction in positive symptoms and extrapyramidal motor side effects of schizophrenia. Conversely, aripiprazole is thought to act as a functional agonist in the mesocortical pathway, where reduced dopamine activity is associated with negative symptoms and cognitive impairment. The antagonistic effect of aripiprazole on 5-HT2A receptors may alleviate negative symptoms and cognitive impairment in schizophrenia. 5-HT2A receptors are Gi/Go-coupled receptors that, upon activation, inhibit neuronal activity by reducing neuronal excitability and decreasing neurotransmitter release at nerve endings. In the substantia nigra-striatal pathway, 5-HT2A receptors regulate dopamine release. Aripiprazole, by antagonizing 5-HT2A receptors, relieves the inhibition of dopamine release in the striatum and increases neurotransmitter levels at nerve endings. The combined effect of D2 receptor and 5-HT2A receptor antagonism is thought to counteract the increased extrapyramidal side effects caused by enhanced dopamine function. Blocking 5-HT2A receptors may also lead to the regulation of glutamate release in the midbrain cortex circuit; glutamate is a neurotransmitter that plays a role in schizophrenia. 5-HT1A receptors are autoreceptors that inhibit 5-HT release upon activation. Aripiprazole is a partial agonist of these receptors, reducing 5-HT release. This leads to enhanced dopamine release in the striatum and prefrontal cortex. Therapeutic doses of aripiprazole have been reported to occupy up to 90% of the brain's D2 receptors in a dose-dependent manner. Aripiprazole targets different receptors, leading to drug-related adverse reactions; for example, its antagonism of α1-adrenergic receptors can cause orthostatic hypotension. Antagonism of histamine H1 receptors may explain the drowsiness observed after taking the drug. Schizophrenia is a chronic illness that patients experience remission and relapse throughout their lives. Antipsychotic medications are the primary means of treating this illness. Long-acting injectable (LAI) antipsychotics are an ideal alternative to oral formulations because they can improve patient adherence. Many second-generation antipsychotics (SGAs) are available in long-acting injectable formulations. These include paliperidone, aripiprazole, olanzapine, and risperidone. This article reviews the most recently developed and approved formulations of these drugs—aripiperazole monohydrate, aripiprazole-loprolate, and paliperidone palmitate. While these drugs were initially formulated as once-monthly doses, a three-monthly injectable formulation of paliperidone palmitate has been approved, marking the first long-acting injectable to extend the dosing interval beyond the usual monthly dose. In addition, aripiprazole lorazepam formulations every six and eight weeks have been developed. All long-acting injectable formulations of second-generation antipsychotics have shown superior efficacy compared to placebo and comparable safety and tolerability to their corresponding oral formulations (if injection site reactions are ignored). Long-acting injectable formulations of first-generation antipsychotics (e.g., haloperidol decanoate) have recently been compared with long-acting injectable formulations of second-generation antipsychotics, with comparable efficacy and both showing the expected adverse reactions of their respective drugs. Despite the availability of long-acting injectables (LAIs), their use remains challenging. Educating patients and clinicians about the use of long-acting injectables and continuing to develop these drugs are important steps to ensure that patients most likely to benefit from them have access to them. [1]

---

Aripiprazole lauroxil is a long-acting injectable prodrug of aripiprazole, designed for intramuscular administration. It was developed to provide sustained plasma concentrations of aripiprazole, allowing for once-monthly dosing in the treatment of psychiatric disorders such as schizophrenia. [1]
- The prodrug is formed by N-acycloxymethyl derivatization of the lactam moiety of aripiprazole. This modification significantly alters the physicochemical properties of the drug, enabling its formulation as an injectable depot suspension. [1]
- This study is one of the first to simultaneously quantify the prodrug, its intermediate, and the parent drug in vivo, confirming the hypothesized two-step conversion pathway. The authors note that developing bioanalytical methods for such short-lived intermediates is challenging, and that accurate prediction of human pharmacokinetics is complicated by interspecies differences in esterase activity. They stress the importance of thoroughly evaluating the pharmacological and toxicological potential of any intermediates formed during prodrug conversion to ensure patient safety. [1]

659.326

C, 65.44; H, 7.78; Cl, 10.73; N, 6.36; O, 9.69

1259305-29-7

129722-12-9;851220-85-4 (hydrate);1259305-26-4 (cavoxil);1259305-29-7 (lauroxil);

49831411

White to off-white solid powder

81-83

8.743

0

6

20

45

858

0

CCCCCCCCCCCC(=O)OCN1C2=C(C=CC(=C2)OCCCCN3CCN(CC3)C4=CC=CC(=C4Cl)Cl)CCC1=O

DDINXHAORAAYAD-UHFFFAOYSA-N

InChI=1S/C36H51Cl2N3O4/c1-2-3-4-5-6-7-8-9-10-16-35(43)45-28-41-33-27-30(19-17-29(33)18-20-34(41)42)44-26-12-11-21-39-22-24-40(25-23-39)32-15-13-14-31(37)36(32)38/h13-15,17,19,27H,2-12,16,18,20-26,28H2,1H3

[7-[4-[4-(2,3-dichlorophenyl)piperazin-1-yl]butoxy]-2-oxo-3,4-dihydroquinolin-1-yl]methyl dodecanoate

Aripiprazole lauroxil; 1259305-29-7; Aristada; RDC-3317; ALKS 9072; Aristada initio; ALKS 9070; RDC 3317;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~8.33 mg/mL (~12.61 mM)

Solubility in Formulation 1: ≥ 0.83 mg/mL (1.26 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 8.3 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

 (Please use freshly prepared in vivo formulations for optimal results.)