Propofol for treatment of refractory seizures in dogs and a cat with intracranial disorders

Twelve dogs and one cat that were presented with seizures due to various disorders of intracranial origin were treated with one or several boluses of propofol (2 to 8 mg/kg). All the animals had received previous medication, including diazepam alone or in combination with phenobarbital and/or pentobarbital. Seizure control with prevention of further convulsions was achieved in 11 patients. In one dog, seizures kept recurring after periods of successful control following administration of propofol. Another dog with continuing seizures resistant to barbiturate therapy died following administration of propofol. This retrospective study suggests that propofol may be an effective drug in controlling status epilepticus resistant to conventional medication and may be used as an alternative to pentobarbital administration.     

Activation procedures in the electroencephalograms of healthy and epileptic cats under propofol anaesthesia

The current study evaluated the diagnostic value of electroencephalographic recordings (EEG) in cats with epilepsy under special consideration of photic stimulation and hyperventilation. EEGs in six healthy cats were recorded under light (mean dose of 0.23 mg/kg/min) and deep (mean dose of 0.7 mg/kg/min) propofol anaesthesia, whereas EEGs in 13 diseased cats were recorded under a propofol anaesthesia which was kept as light as possible (mean dose of 0.39 mg/kg/min). Paroxysmal discharges were detected in six of 13 cats suffering from seizures (two cats with idiopathic epilepsy and four cats with symptomatic epilepsy). Activation techniques did not enhance the diagnostic value of the EEGs. Photic driving was detected in one of six healthy cats under light, in five of six healthy cats under deep propofol anaesthesia and in 11 of 13 cats with seizures. Systematic use of activation techniques does not seem to increase the diagnostic yield of the recorded EEGs and should not be used in a clinical setting until future studies indicate value. Further investigations into the origin of photic driving under propofol anaesthesia are needed and could lead to the development of a reliable animal model to research into drug effects on the EEG.     

Clinical evaluation of a new formulation of propofol in a medium-chain and long-chain triglycerides emulsion in dogs

Propofol formulated in a mixed medium-chain and long-chain triglycerides emulsion has been recently introduced for clinical use as an alternative to the conventional long-chain triglycerides formulation. This prospective multicentric study evaluated the clinical effectiveness and the complications associated with the use of this new formulation of propofol in dogs. Forty-six Spanish veterinary clinics participated in this study. A total of 541 anaesthesias (118 ASA I, 290 ASA II, 101 ASA III and 32 ASA IV) performed for various diagnostic and therapeutic purposes were evaluated. The anaesthetic protocol was not controlled, with the exception that propofol had to be used at least for induction of anaesthesia. The induction dose of propofol and the incidence of anaesthetic complications throughout the procedure were recorded. A chi-square test compared the incidence of complications according to the maintenance agent used (propofol vs. inhalatory anaesthesia), anaesthetic risk (ASA classification) and the reason for the anaesthesia. The patients premedicated with alpha2 agonists needed lower doses (mean +/- SD, 2.9 +/- 1.3 mg/kg i.v.) than the animals premedicated with phenothiazines (3.9 +/- 1.4 mg/kg i.v.) or benzodiazepines (4.0 +/- 1.4 mg/kg i.v.). The most frequent complications were difficult endotracheal intubation (1.3%), postinduction apnoea (11.3%), cyanosis (0.6%), bradypnoea (2.6%), tachypnoea (2.8%), bradycardia (2%), tachycardia (2.6%), hypotension (0.2%), shock (0.2%), vomiting (4.6%), epileptiform seizures (2.8%), premature awakening (7.4%) and delayed recovery (0.9%). There were no cases of pain on injection or aspiration pneumonia. Three dogs died (0.55%), one during induction and two during recovery from anaesthesia. This study demonstrates that the new formulation of propofol is an useful and effective drug to induce general anaesthesia in dogs.     

Median effective dosage of propofol for induction of anesthesia in dogs.

The median effective dosage (ED50) of propofol for induction of anesthesia was determined in 25 dogs premedicated with acepromazine, 0.05 mg/kg of body weight, and in 35 unpremedicated dogs. The ED50 was found to be 2.2 mg/kg in premedicated dogs and was 3.8 mg/kg in unpremedicated dogs. The mean +/- SD total dosage of propofol required to induce anesthesia in premedicated animals was 2.8 +/- 0.5 mg/kg and was 4.7 +/- 1.3 mg/kg in unpremedicated animals. Signs of excitement were observed in 5 of the unpremedicated dogs, but in none of those that were premedicated.     

Induction of anaesthesia in dogs and cats with propofol

Propofol was used to induce anaesthesia in 89 dogs and 13 cats of either sex, various breeds and of widely different ages and weights; they varied considerably in physical condition and were anaesthetised for a variety of investigations and surgical procedures. They were premedicated with acepromazine, papaveretum, diazepam, pethidine, atropine and scopolamine in different combinations. After induction with propofol, anaesthesia was maintained with halothane, isoflurane, methoxyflurane and enflurane and, or, nitrous oxide. The mean (+/- sd) induction doses of propofol in unpremedicated and premedicated animals were 5.2 +/- 2.3 mg/kg and 3.6 +/- 1.4 mg/kg respectively for dogs, and 5.0 +/- 2.8 mg/kg and 5.3 +/- 4.3 mg/kg for cats. There were no differences between the sexes. Premedication did not affect recovery times. The incidence of side effects was very low. One dog showed evidence of pain when propofol was injected. No incompatibility was observed between propofol and the premedicants and other anaesthetic agents used.     

Real time monitoring of propofol blood concentration in ponies anaesthetized with propofol and ketamine

This study examined the pharmacokinetics of propofol by infusion in ponies using an analyser for the rapid measurement of propofol concentrations. The analyser (Pelorus 1000; Sphere Medical Ltd., Cambridge, UK) has a measurement cycle of approximately five minutes. Ten Welsh‐cross ponies (weighing 135–300 kg) undergoing minor procedures were studied after premedication with acepromazine 0.03 mg/kg and detomidine 0.015 mg/kg. Anaesthesia was induced with ketamine 2 mg/kg and diazepam 0.03 mg/kg, and maintained with an infusion of propofol at an initial rate of 0.16 mg/kg/min for the first thirty minutes, after a bolus of 0.3 mg/kg; and ketamine by infusion (20–40 μg/kg/min). Blood samples (<2 mL) were collected prior to, during and after the infusion, and on assuming standing position. Anaesthesia was uneventful; with the duration of infusion 31–89 min. Blood propofol concentrations during the infusion ranged between 1.52 and 7.65 μg/mL; pseudo‐steady state concentrations 3.64–6.78 μg/mL, and concentrations on assuming standing position 0.75–1.40 μg/mL. Propofol clearance and volume of distribution were 31.4 (SD 6.1) mL/min/kg and 220.7 (132.0) mL/kg, respectively. The propofol analyser allows titration of propofol to a given concentration; and may be useful for anaesthesia in animals where kinetics are unknown; in disease states; and where intercurrent therapies affect propofol disposition.     

Clinical evaluation of propofol as an intravenous anaesthetic agent in cats and dogs

The clinical efficacy and safety of an emulsion containing 10 mg/ml of the intravenous anaesthetic propofol were evaluated in cats and dogs by veterinary surgeons in eight practices in the United Kingdom. A total of 290 dogs and 207 cats were anaesthetised with propofol either as a single injection for procedures of short duration, or as an induction agent with maintenance provided by further incremental injections or as an induction agent with maintenance by gaseous agents. The mean induction doses of propofol for unpremedicated dogs and cats were respectively 6.55 mg/kg and 8.03 mg/kg. The mean induction doses after premedication with a tranquilliser were 4.5 mg/kg and 5.97 mg/kg for dogs and cats, respectively. Mean recovery times ranged, depending on the method of anaesthesia, from 23 to 40 minutes in dogs and from 27 to 38 minutes in cats; recovery was defined as the time at which the animals were alert and able to stand. Adverse side effects were infrequent, apnoea during induction being the commonest. Acepromazine and atropine were most often used as premedicants although in a few cases diazepam, xylazine and other agents were employed. No clinical incompatibility was observed between propofol and any of the other agents administered during the study. The rapid and usually excitement-free recovery of the animals was a valuable feature of anaesthesia with propofol.     

Clinical usefulness of propofol as an anesthetic induction agent in dogs and cats

Propofol was used as an induction agent of general anesthesia in 77 dogs and 64 cats, all client owned, for a variety of surgeries/treatments or diagnostic procedures. The mean intravenous doses of propofol required to achieve endotracheal intubation in dogs and cats were 6.5 +/- 1.4 mg/kg and 10.1 +/- 2.8 mg /kg, respectively. Most of the animals could be induced to anesthesia smoothly by the administration of propofol with a high incidence of apnea. Propofol is a clinically valuable anesthetic induction agent in both dogs and cats, however, care must be taken for apnea.     

Evaluation of propofol and medetomidine-ketamine for short-term immobilization of Gulf of Mexico sturgeon (Acipenser oxyrinchus de soti).

Parenteral anesthetic protocols for short-term immobilization were evaluated in twenty 4-yr-old Gulf of Mexico sturgeon (Acipenser oxyrinchus de soti). An initial dose-response trial determined the efficacy of either propofol (3.5-7.5 mg/kg. i.v.) or combinations of medetomidine (0.03-0.07 mg/kg, i.m.)-ketamine (3-7 mg/kg, i.m.). A subsequent study evaluated the physiologic effects of propofol (6.5 mg/kg, i.v.)-induced anesthesia and anesthesia induced with a medetomidine (0.06 mg/kg, i.m.)-ketamine (6 mg/kg i.m.) combination. The effects of medetomidine were reversed at 30 min with atipamezole (0.30 mg/kg, i.m.). Both drug protocols provided adequate short-term immobilization for minor diagnostic procedures. Sturgeon receiving propofol were in a light plane of anesthesia within 5 min after drug administration, whereas only 30% of the medetomidine-ketamine group reached a light plane of anesthesia in the same time period. Both propofol and medetomidine-ketamine resulted in mild bradycardia and apparent respiratory depression, with propofol producing more profound effects. At the dosages used in this study, both propofol and the medetomidine-ketamine combination effectively induced a light plane of anesthesia. Induction times were shorter in the propofol group.     

Effect of variable-dose propofol alone and in combination with two fixed doses of ketamine for total intravenous anesthesia in cats

OBJECTIVE: To determine the minimum infusion rate (MIR50) for propofol alone and in combination with ketamine required to attenuate reflexes commonly used in the assessment of anesthetic depth in cats. ANIMALS: 6 cats. PROCEDURE: Propofol infusion started at 0.05 to 0.1 mg/kg/min for propofol alone or 0.025 mg/kg/min for propofol and ketamine (low-dose ILD] constant rate infusion [CRI] of 23 microg/kg/min or high-dose [HD] CRI of 46 microg/kg/min), and after 15 minutes, responses of different reflexes were tested. Following a response, the propofol dose was increased by 0.05 mg/kg/min for propofol alone or 0.025 mg/kg/min for propofol and ketamine, and after 15 minutes, reflexes were retested. RESULTS: The MIR50 for propofol alone required to attenuate blinking in response to touching the medial canthus or eyelashes; swallowing in response to placement of a finger or laryngoscope in the pharynx; and to toe pinch, tetanus, and tail-clamp stimuli were determined. Addition of LD ketamine to propofol significantly decreased MIR50, compared with propofol alone, for medial canthus, eyelash, finger, toe pinch, and tetanus stimuli but did not change those for laryngoscope or tail-clamp stimuli. Addition of HD ketamine to propofol significantly decreased MIR50, compared with propofol alone, for medial canthus, eyelash, toe pinch, tetanus, and tail-clamp stimuli but did not change finger or laryngoscope responses. CONCLUSIONS AND CLINICAL RELEVANCE: Propofol alone or combined with ketamine may be used for total IV anesthesia in healthy cats at the infusion rates determined in this study for attenuation of specific reflex activity.     

Anesthesia of Tibetan yak (Bos grunniens) using thiafentanil - xylazine and carfentanil - xylazine

The use of 0.025 +/- 0.012 mg/kg (median +/- interquartile range) thiafentanil with 0.15 +/- 0.03 mg/kg xylazine (TX) and 0.011 +/- 0.0015 mg/kg carfentanil with 0.25 +/- 0.093 mg/kg xylazine (CX), with dosages based on estimated bodyweight, was used in the anesthesia of 37 Tibetan yak (Bos grunniens) housed within a drive-through animal park setting. The median time to lateral recumbency was 5 and 7 min for each group, respectively. With the addition of propofol in 8 CX animals and 17 TX animals, the anesthetic plane was suitable for a wide range of procedures. The median time to standing recovery following administration of naltrexone was 4 +/- 3.5 min with TX and 7 +/- 1.5 min with CX. There was one fatality and one case of renarcotization in the TX group. Overall, the dosages used in the study provided a reliable and useful anesthetic induction protocol, with TX animals demonstrating a more rapid induction and recovery with less cardiac depression than CX animals.     

The use of propofol for induction of anaesthesia in dogs premedicated with acepromazine, butorphanol and acepromazine-butorphanol

Cardiovascular, pulmonary and anaesthetic-analgesic responses were evaluated in 18 male and female dogs to determine the effect of the injectable anaesthetic propofol used in conjuction with acepromazine and butorphanol. The dogs were randomly divided into three groups. Dogs in Group A were premeditated with 0.1 mg/kg of intramuscular acepromazine followed by an induction dose of 4.4 mg/kg of intravenous propofol; Group B received 0.2 mg/kg of intramuscular butorphanol and 4.4 mg/kg of intravenous propofol; dogs in Group AB were administered a premeditation combination of 0.1 mg/kg of intramuscular acepromazine and 0.2 mg/kg of intramuscular butorphanol, followed by induction with 3.3 mg/kg of intravenous propofol. The induction dose of propofol was given over a period of 30-60 seconds to determine responses and duration of anaesthesia. Observations recorded in the dogs included heart and respiratory rates, indirect arterial blood pressures (systolic, diastolic and mean), cardiac rhythm, end-tidal CO, tension, oxygen saturation, induction time, duration of anaesthesia, recovery time and adverse reactions. The depth of anaesthesia was assessed by the response to mechanical noxious stimuli (tail clamping), the degree of muscle relaxation and the strength of reflexes. Significant respiratory depression was seen after propofol induction in both groups receiving butorphanol with or without acepromazine. The incidence of apnea was 4/6 dogs in Group B, and 5/6 dogs in Group AB. The incidence of apnea was also correlated to the rate of propofol administration. Propofol-mediated decreases in arterial blood pressure were observed in all three groups. Moderate bradycardia (minimum value > 55 beats/min) was observed in both Groups B and AB. There were no cardiac dysrhythmias noted in any of the 18 dogs. The anaesthetic duration and recovery times were longer in dogs premeditated with acepromazine/butorphanol.     

Effects of an intravenous bolus of alfaxalone versus propofol on intraocular pressure in sheep

The objective of this prospective study was to determine the effects of a single intravenous bolus of alfaxalone in 2-hydroxypropyl-β-cyclodextrin and propofol on the intraocular pressure (IOP) in sheep. Ten Ripollesa sheep with a bodyweight of 48.5 (6.8) kg (mean [sd]) were used in the study. Twenty-four hours before the experimental procedure, a complete ophthalmic examination was performed in all animals. The day of the study, intravenous alfaxalone (2 mg/kg) or propofol (6 mg/kg) was randomly administered in a cross-over design, with a washout period of two weeks. Measurements of IOP, globe position and pupil size were obtained at basal time, before induction (time 0) and at two, five, 10, 15, 20, 30, 45, 60, 90 and 120 minutes after drug administration. Occasional side effects and time to standing were also noted. Intravenous administration of alfaxalone and propofol in sheep resulted in no alteration of IOP. Nevertheless, a decrease in the pupil size was observed in both groups. This present study shows that alfaxalone and propofol, administrated as a single intravenous bolus, are good options for maintaining IOP during anaesthesia in sheep, although marked miosis was observed after administration.     

Evaluating the Clinical and Cardiopulmonary Effects of Clove Oil and Propofol in Tiger Salamanders (Ambystoma tigrinum)

Our understanding of clinical anesthesia for amphibians is limited. This study represents the first attempt to evaluate the effectiveness of clove oil and propofol as anesthetic agents for tiger salamanders (Ambystoma tigrinum). Twelve apparently healthy adult tiger salamanders were anesthetized in a water bath containing clove oil (450 mg/L of water). After a 2-week wash-out period, 11 of the salamanders were used to evaluate the effectiveness of propofol as an anesthetic agent. Propofol was administered intracoelomically at a dose of 25 mg/kg (n = 5) or 35 mg/kg (n = 6). Heart and respiratory rates were monitored at 5-, 10-, 15-, 20-, 30-, 40-, 50-, 60-, 70-, 80-, 90-, 100-, 120-, 150-, and 180-minute intervals after exposure to the anesthetics. Righting, escape, corneal, superficial pain, and deep pain reflexes were also monitored at these time intervals and ranked as (1) normal, (2) slow, or (3) absent. Surgical anesthesia was determined to be when all of the reflexes were lost. Clove oil produced a surgical level of anesthesia in 67% (8/12) of the salamanders. Propofol administered at 25 mg/kg produced surgical anesthesia in 40% (2/5) of the salamanders, whereas propofol at 35 mg/kg produced surgical anesthesia in 83% (5/6) of the animals. Clove oil did not significantly (P > 0.05) affect respiratory rate at any time, but did decrease heart rate significantly (P < 0.05) after 30 minutes. Propofol produced a significant (P < 0.05) reduction in the respiratory rate at both doses. Heart rate was also found to decrease significantly (P < 0.05) for propofol at 25 mg/kg after 90 minutes and for propofol at 35 mg/kg at 60 minutes and after 80 minutes. Both clove oil and propofol were found to provide a surgical plane of anesthesia for tiger salamanders. However, clove oil provided more rapid onset of the desired level of anesthesia with a longer duration. Although the intracoelomic route for propofol was effective, the time to surgical anesthesia was prolonged. These anesthetics show promise and may prove useful to veterinarians or field biologists working with urodelans.     

Total intravenous anaesthesia with propofol or propofol/ketamine in spontaneously breathing dogs premedicated with medetomidine

The cardiorespiratory parameters, the depth of anaesthesia and the quality of recovery were evaluated in six spontaneously breathing dogs that had been premedicated with medetomidine (40 microg/kg, supplemented with 20 microg/kg an hour later), administered with either propofol (1 mg/kg followed by 0.15 mg/kg/minute, intravenously), or with ketamine (1 mg/kg followed by 2 mg/kg/hour, intravenously) and propofol (0.5 mg/kg followed by 0.075 mg/kg/minute, intravenously). The dogs' heart rate and mean arterial blood pressure were higher and their minute volume of respiration and temperature were lower when they were anaesthetised with propofol plus ketamine, and a progressive hypercapnia leading to respiratory acidosis was more pronounced. When the dogs were anaesthetised with propofol/ketamine they recovered more quickly, but suffered some unwanted side effects. When the dogs were anaesthetised with propofol alone they recovered more slowly but uneventfully.     

Clinical use of dexmedetomidine as premedicant in cats undergoing propofol-sevoflurane anaesthesia

The purpose of this report was to evaluate the cardiorespiratory effects and efficacy of dexmedetomidine as a premedicant agent in cats undergoing ovariohysterectomy anaesthetized with propofol-sevoflurane. Cats were randomly divided into two groups of eight animals each. Dexmedetomidine (0.01 mg/kg) or 0.9% saline was administered intravenously (D and S, respectively). After 5 min, propofol was administered intravenously and anaesthesia was maintained with sevoflurane. Heart and respiratory rates, arterial blood pressure, oxygen saturation, rectal temperature and the amount of propofol needed for induction were measured. Premedication with dexmedetomidine reduced the requirement of propofol (6.7+/-3.8 mg/kg), but induced bradycardia, compared with the administration of saline (15.1+/-5.1 mg/kg). Recovery quality was significantly better in D but no significant difference in time to return of swallowing reflex was observed between groups (D=2.5+/-0.5 min; S=3.2+/-1.8 min). In conclusion, dexmedetomidine is a safe and effective agent for premedication in cats undergoing propofol-sevoflurane anaesthesia with minimal adverse effects.     

Cardiopulmonary effects of prolonged anesthesia via propofol-medetomidine infusion in ponies

OBJECTIVE: To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery. ANIMALS: 10 ponies. PROCEDURE: After sedation was induced by IV administration of medetomidine (7 microg/kg of body weight), anesthesia was induced by IV administration of propofol 12 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 microg/kg per hour) and propofol 10.07 to 0.11 mg/kg per minute). Spontaneous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during anesthesia. Five ponies received atipamezole (60 microg/kg) during recovery. RESULTS: During anesthesia, mean cardiac index and heart rate increased significantly until 150 minutes, then decreased until cessation of anesthesia. Mean arterial pressure and systemic vascular resistance index increased significantly between 150 minutes and 4 hours. In 4 ponies, PaO2 decreased to < 60 mm Hg. Mean blood propofol concentrations from 20 minutes after induction onwards ranged from 2.3 to 3.5 microg/ml. Recoveries were without complications and were complete within 28 minutes with atipamezole administration and 39 minutes without atipamezole administration. CONCLUSIONS AND CLINICAL RELEVANCE: During total IV anesthesia of long duration with medetomidine-propofol, cardiovascular function is comparable to or better than under inhalation anesthesia. This technique may prove suitable in equids in which prompt recovery is essential; however, in some animals severe hypoxia may develop and oxygen supplementation may be necessary.     

Electroencephalographic evaluation of gold wire implants inserted in acupuncture points in dogs with epileptic seizures

The purpose of this study was to evaluate both, clinically and with electroencephalographic (EEG) recordings, the effect of gold wire implants in acupuncture points in dogs with uncontrolled idiopathic epileptic seizures. Fifteen dogs with such diagnosis were enrolled in the study. A first EEG recording was performed in all dogs under anaesthesia with xylazine (1 mg/kg) and propofol (6 mg/kg) before the treatment protocol, and a second EEG was performed 15 weeks later. Relative frequency power, intrahemispheric coherence available through EEG, number of seizures and seizure severity were compared before and after treatment using a Wilcoxon signed-rank test. There were no significant statistical differences before and after treatment in relative power or in intrahemispheric coherence in the EEG recording. However, there was a significant mean difference in seizure frequency and seizure severity between control and treatment periods. After treatment, nine of the 15 dogs (60%) had at least a 50% reduction in seizures frequency during the 15 weeks established as follow-up of this treatment.     

Anesthetic and cardiorespiratory effects of a 1:1 mixture of propofol and thiopental sodium in dogs.

OBJECTIVE: To compare anesthetic and cardiorespiratory effects of a 1:1 (vol:vol) mixture of propofol and thiopental sodium with either drug used alone in dogs. DESIGN: Randomized crossover study. ANIMALS: 10 healthy Walker Hounds. PROCEDURE: Dogs received propofol (6 mg/kg [2.7 mg/lb] of body weight), thiopental (15 mg/kg [6.8 mg/lb]), or a mixture of propofol (6 mg/kg) and thiopental (15 mg/kg) at 1-week intervals. Drugs were slowly administered i.v. over 90 seconds or until dogs lost consciousness. Increments of 10% of the initial dose were administered until intubation was possible. Amount of drug required for intubation, quality of induction and recovery, times from induction to intubation and to walking with minimal ataxia, and duration of intubation and lateral recumbency were recorded. Heart and respiratory rates, mean, systolic, and diastolic blood pressure, hemoglobin saturation of oxygen (SpO2), and end-tidal CO2 concentration (ETCO2) were determined before and after intubation. RESULTS: Amounts of propofol and thiopental required to permit intubation were less, but not significantly so, when administered in combination than when administered alone. Duration of lateral recumbency and time from induction to walking were greater and recovery quality was worse in the thiopental group, compared with the other groups. Dogs in all groups remained normotensive. Respiratory rate, heart rate, ETCO2, and SpO2 did not differ among groups. CONCLUSIONS AND CLINICAL RELEVANCE: A 1:1 mixture of propofol and thiopental induced anesthesia of similar quality to propofol or thiopental alone. Recovery quality and recovery times were similar to those of propofol and superior to those of thiopental.     

Evaluation of the predictive performance of a pharmacokinetic model for propofol in Japanese macaques (Macaca fuscata fuscata)

Miyabe‐Nishiwaki, T., Masui, K., Kaneko, A., Nishiwaki, K., Nishio, T., Kanazawa, H. Evaluation of the predictive performance of a pharmacokinetic model for propofol in Japanese macaques (Macaca fuscata fuscata). J. vet. Pharmacol. Therap.  36 , 169–173. Propofol is a short‐acting intravenous anesthetic used for induction/maintenance anesthesia. The objective of this study was to assess a population pharmacokinetic (PPK) model for Japanese macaques during a step‐down infusion of propofol. Five male Japanese macaques were immobilized with ketamine (10 mg/kg) and atropine (0.02 mg/kg). A bolus dose of propofol (5 mg/kg) was administrated intravenously (360 mg/kg/h) followed by step‐down infusion at 40 mg/kg/h for 10 min, 20 mg/kg/h for 10 min, and then 15 mg/kg/h for 100 min. Venous blood samples were repeatedly collected following the administration. The plasma concentration of propofol (Cp) was measured by high‐speed LC‐FL. PPK analyses were performed using NONMEM VII. Median absolute prediction error and median prediction error (MDPE), the indices of prediction inaccuracy and bias, respectively, were calculated, and PE ? individual MDPE vs. time was depicted to show the variability of prediction errors. In addition, we developed another population pharmacokinetic model using previous and current datasets. The previous PK model achieved stable prediction of propofol Cp throughout the study period, although it underestimates Cp. The step‐down infusion regimen described in this study would be feasible in macaques during noninvasive procedures.