Pharmacokinetic Characterisation and Comparison of Bioavailability of Intranasal Fentanyl, Transmucosal, and Intravenous Administration through a Three-Way Crossover Study in 24 Healthy Volunteers

Pharmacokinetics of Intranasal Drugs, Still a Missed Opportunity?

The intranasal (IN) route of administration is important for topical drugs and drugs intended to act systemically. More recently, direct nose-to-brain input was considered to bypass the blood-brain barrier.Processes related to IN absorption and nose-to-brain distribution are complex and depend, sometimes in contrasting ways, on chemico-physical and structural parameters of the compounds, and on formulation options.Due to the intricacies of these processes and despite the large number of articles published on many different IN compounds, it appears that absorption after IN dosing is not yet fully understood. In particular, at variance of the understanding and modelling approaches that are available for predicting the pharmacokinetics (PK) following oral administration of xenobiotics, it appears that there is not a similar understanding of the chemico-physical and structural determinants influencing drug absorption and disposition of compounds after IN administration, which represents a missed opportunity for this research field. This is even more true regarding the understanding of the direct nose-to-brain input. Due to this, IN administrations may represent an interesting and open research field for scientists aiming to develop PK property predictions tools, mechanistic PK models describing rate and extent of IN absorption, and translational tools to anticipate the clinical PK following IN dosing based on in vitro and in vivo non clinical experiments.This review intends to provide: i) some basic knowledge related to the physiology of PK after IN dosing, ii) a non-exhaustive list of preclinical and clinical examples related to compounds explored for the potential nose-to-blood and nose-to-brain passage, and iii) the identification of some areas requiring improvements, the understanding of which may facilitate the development of IN drug candidates.

Advances in fentanyl testing

Fentanyl is a synthetic opioid that was approved by the FDA in the late 1960s. In the decades since, non-prescription use of fentanyl, its analogs, and structurally unrelated novel synthetic opioids (NSO) has become a worsening public health crisis. There is a clear need for accessible testing for these substances in biological specimens and in apprehended drugs. Immunoassays for fentanyl in urine are available but their performance is restricted to facilities that hold moderate complexity laboratory licenses. Immunoassays for other matrices such as oral fluid (OF), blood, and meconium have been developed but are not widely available. Point of care tests (POCT), such as lateral flow immunoassays or fentanyl test strips (FTS), are widely available but not approved by the FDA for clinical use. All immunoassays are vulnerable to false positive and false negative results. Immunoassays may or may not be able to detect fentanyl analogs and NSOs. Mass spectrometry (MS) can accurately and reliably measure fentanyl and its major metabolite norfentanyl in urine and oral fluid. MS is available at reference laboratories and large hospitals. Liquid chromatography paired with tandem mass spectrometry (LC-MS/MS) is the most widely used method and has outstanding specificity and sensitivity for fentanyl and norfentanyl. When compared to immunoassays, MS is more expensive, requires more technical skill, and takes longer to result. Newer mass spectrometry methods can measure fentanyl analogs and NSO. Both mass spectrometry assays and immunoassays [in the form of fentanyl test strips (FTS)] have potential use in harm reduction programs.

Effect of Intranasal Dexamethasone on the Incidence of Nausea and Vomiting After Adult Strabismus Surgery

Objectives

Due to the high prevalence of postoperative nausea and vomiting (PONV), this study aimed to determine the preventive effect of intranasal dexamethasone on the incidence of nausea and vomiting after adult strabismus surgery.

Methods

This randomized clinical trial study was performed on 72 patient candidates for strabismus surgery at Feiz University Hospital in Isfahan in 2020. Patients were divided into 2 groups of 36 with random allocation software and entered into the study. After induction of similar anesthesia, endotracheal intubation was performed in patients. Immediately after inflating the cuff, the first group (intranasal dexamethasone (ND)) received 1 mL of dexamethasone (4 mg) per nasal passage, and the second group (intranasal normal saline (NS)) received 1 mL of normal saline per nasal passage. Patients of the 2 groups were evaluated and compared at first 2 hours and 2 - 24 hours after surgery for the incidence and severity of nausea and vomiting, and pain after surgery. Data were analyzed using SPSS software version 23.

Results

There were no significant differences in terms of age (P = 0.304), weight (P = 0.21), gender (P = 0.81), and American Society of Anesthesiologists (ASA) Physical Status class (P = 1) between the 2 groups. In the first 2 hours after surgery, the incidence of nausea (P = 0.034) and its severity (P = 0.019) was significantly lower in the ND group compared to the NS group. Also, 24 hours after surgery, the incidence of nausea (P = 0.38) and its severity (P = 0.55) were insignificantly lower in the ND group. Both groups showed no significant difference in the incidence of vomiting at 2 hours (P = 0.11) and 24 hours (P = 0.16) postoperative. Two hours after surgery, the incidence of pain (P = 0.001) and its severity (P < 0.001), and also 24 hours after surgery, the incidence of pain (P < 0.001) and its severity (P < 0.001) were significantly lower in the ND group. Getting ondansetron (P = 0.023) and pethidine (P < 0.001), extubation time (P < 0.001), and recovery time (P = 0.03) were significantly lower in the ND group. Patients' satisfaction was significantly higher in the ND group compared to the NS group (P = 0.031).

Conclusions

The findings of the present study show that the intranasal use of dexamethasone with a dose of 8 mg compared to saline is associated with a decrease in PONV and postoperative pain, a decrease in the use of ondansetron and pethidine, and an increase in patient's satisfaction. Intranasal use of dexamethasone may be an effective and safe method, especially in cases where we do not have access to an intravenous line.

Pharmacokinetic Characterization of the DDAH1 Inhibitors ZST316 and ZST152 in Mice Using a HPLC-MS/MS Method

The pharmacokinetic profile of ZST316 and ZST152, arginine analogues with inhibitory activity towards human dimethylarginine dimethylaminohydrolase-1 (DDAH1), was investigated in mice using a newly developed HPLC-MS/MS method. The method proved to be reproducible, precise, and accurate for the measurement of the compounds in plasma and urine. Four-week-old female FVB mice received a single dose of ZST316 and ZST152 by intravenous bolus (30 mg/Kg) and oral gavage (60 mg/Kg). ZST316 Cmax was 67.4 µg/mL (intravenous) and 1.02 µg/mL (oral), with a half-life of 6 h and bioavailability of 4.7%. ZST152 Cmax was 24.9 µg/mL (intravenous) and 1.65 µg/mL (oral), with a half-life of 1.2 h and bioavailability of 33.3%. Urinary excretion of ZST152 and ZST316 was 12.5%–22.2% and 2.3%–7.5%, respectively. At least eight urinary metabolites were identified. After chronic intraperitoneal treatment with the more potent DDAH1 inhibitor, ZST316 (30 mg/Kg/day for three weeks), the bioavailability was 59% and no accumulation was observed. Treatment was well tolerated with no changes in body weight vs. untreated animals and no clinical signs of toxicity or distress. The results of this study show that ZST316 has a favorable pharmacokinetic profile, following intraperitoneal administration, to investigate the effects of DDAH1 inhibition in mice.