Determination of orphenadrine plasma levels using HPLC with diode array detection and a novel solid-phase extraction procedure in psychiatric patients

Clinical outcomes associated with orphenadrine deliberate self-poisoning: a retrospective poisons centre study

INTRODUCTION

Orphenadrine overdoses can cause antimuscarinic toxicity, respiratory failure, refractory seizures and cardiotoxicity. The dose-toxicity relationship is poorly defined. Orphenadrine is marketed as immediate and sustained release formulations, and it is not known how the formulation impacts on toxicity. We determined the clinical toxicity of orphenadrine in patients referred to a regional poisons centre.

METHODS

Retrospective case series of patients in New South Wales with orphenadrine deliberate self-poisoning from January 2016 to April 2022 referred to the New South Wales Poisons Information Centre. Demographics, history of exposure, treatment and outcomes were extracted from clinical databases. Receiver-operating characteristic curves were constructed to determine thresholds predicting toxicity.

RESULTS

Forty-eight patients were identified, with information on clinical outcomes in 46 patients and doses in 41 patients. All patients were older than 12 years. The median orphenadrine dose was 770 mg (range 210-10,000 mg), 59 per cent as the immediate release formulation, and 67 per cent reported coingestants. Doses of sustained release formulations were significantly greater than immediate release formulations, median 2,750 mg versus 595 mg. Common clinical features were drowsiness (59 per cent), sinus tachycardia (37 per cent) and confusion (33 per cent). Three patients had mild hypotension, three were intubated for coma, and two had seizures; no patients suffered ventricular dysrhythmias. All patients survived, with 75 per cent being medically cleared within 24 hours of presentation. A dose-toxicity relationship was observed, but conclusions are limited by the small number of cases with moderate or severe toxicity.

DISCUSSION

All patients survived, and severe cardiac and neurological toxicity were not observed. This contrasts to published case reports noting severe poisoning at similar or lower doses. Formulation may have an impact on outcomes, with lesser toxicity from sustained release products.

CONCLUSIONS

Orphenadrine doses up to 10 g were associated with antimuscarinic toxicity and sedation, but not severe cardiotoxicity. More research exploring the effect of dose and formulation on outcomes is required.

Exploitation of multi-walled carbon nanotubes/Cu(ii)-metal organic framework based glassy carbon electrode for the determination of orphenadrine citrate

Metal organic frameworks (MOFs), with structural tunability, high metal content and large surface area have recently attracted the attention of researchers in the field of electrochemistry. In this work, an unprecedented use of multi-walled carbon nanotubes (MWCNTs)/copper-based metal-organic framework (Cu-BTC MOF) composite as an ion-to-electron transducer in a potentiometric sensor is proposed for the determination of orphenadrine citrate. A comparative study was conducted between three proposed glassy carbon electrodes, Cu-MOF, (MWCNTs) and MWCNTs/Cu-MOF composite based sensors, where Cu-MOF, MWCNTs and their composite were utilized as the ion-to-electron transducers. The sensors were developed for accurate and precise determination of orphenadrine citrate in pharmaceutical dosage form, spiked real human plasma and artificial cerebrospinal fluid (ACSF). The sensors employed β-cyclodextrin as a recognition element with the aid of potassium tetrakis(4-chlorophenyl)borate (KTpCIPB) as a lipophilic ion exchanger. The sensors that were assessed based on the guidelines recommended by IUPAC and demonstrated a linear response within the concentration range of 10-7 M to 10-3 M, 10-6 M to 10-2 M and 10-8 M to 10-2 M for Cu-MOF, MWCNTs and MWCNTs/Cu-MOF composite based sensors, respectively. MWCNTs/Cu-MOF composite based sensor showed superior performance over other sensors regarding lower limit of detection (LOD), wider linearity range and faster response. The sensors demonstrated their potential as effective options for the analysis of orphenadrine citrate in quality control laboratories and in different healthcare activities.

Application of normalized spectra in resolving a challenging Orphenadrine and Paracetamol binary mixture

Normalized spectra have a great power in resolving spectral overlap of challenging Orphenadrine (ORP) and Paracetamol (PAR) binary mixture, four smart techniques utilizing the normalized spectra were used in this work, namely, amplitude modulation (AM), simultaneous area ratio subtraction (SARS), simultaneous derivative spectrophotometry (S(1)DD) and ratio H-point standard addition method (RHPSAM). In AM, peak amplitude at 221.6nm of the division spectra was measured for both ORP and PAR determination, while in SARS, concentration of ORP was determined using the area under the curve from 215nm to 222nm of the regenerated ORP zero order absorption spectra, in S(1)DD, concentration of ORP was determined using the peak amplitude at 224nm of the first derivative ratio spectra. PAR concentration was determined directly at 288nm in the division spectra obtained during the manipulation steps in the previous three methods. The last RHPSAM is a dual wavelength method in which two calibrations were plotted at 216nm and 226nm. RH point is the intersection of the two calibration lines, where ORP and PAR concentrations were directly determined from coordinates of RH point. The proposed methods were applied successfully for the determination of ORP and PAR in their dosage form.