Understanding the concept of extrapolation of dose between species is important for pharmaceutical researchers when initiating new animal or human experiments. Interspecies allometric scaling for dose conversion from animal to human studies is one of the most controversial areas in clinical pharmacology. Allometric approach considers the differences in body surface area, which is associated with animal weight while extrapolating the doses of therapeutic agents among the species. This review provides basic information about translation of doses between species and estimation of starting dose for clinical trials using allometric scaling. The method of calculation of injection volume for parenteral formulation based on human equivalent dose is also briefed.

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Preclinical Research & Development Appropriate translation and determination of the maximum recommended starting dose in human is a vital task in new drug development and research. Allometric scaling is the most frequently used approach for dose extrapolation based on normalization of dose‐to‐body surface area. Misinterpretation of allometric dose conversion and safety factor application can lead to major problems in calculating maximum recommended safe starting dose in first‐in‐human clinical trials. Therefore, dose translation always necessitates careful consideration of body surface area, pharmacological, physiological and anatomical factors, pharmacokinetic parameters, metabolic function, receptor, and life span. The concept of estimating the first‐in‐human dose, interspecies scaling between species and the factors influencing the dose escalation were reviewed. The pros and cons of various approaches to determine first‐in‐human dose including allometric scaling, pharmacokinetically guided approach, minimal anticipated biological effect level, pharmacokinetic–pharmacodynamic modeling, similar drug approach, and microdosing were explained. The five steps to estimate maximum recommended starting dose for human studies by scaling factor were elaborated. Few examples, illustrating the application of different approaches were also demonstrated along with concerns that may be considered while applying such methods. Furthermore, typical considerations in dose administration, dosing through diet, maximum absorbable dose, blood sampling, and anesthesia in animal species were discussed. In summary, this review may serve as a concise guide for predicting human equivalent dose from animal species for researchers involved in various phases of preclinical and early clinical drug development.

Given the distinctive characteristics of both epilepsy and antiepileptic drugs (AEDs), therapeutic drug monitoring (TDM) can make a significant contribution to the field of epilepsy. The measurement and interpretation of serum drug concentrations can be of benefit in the treatment of uncontrollable seizures and in cases of clinical toxicity; it can aid in the individualization of therapy and in adjusting for variable or nonlinear pharmacokinetics; and can be useful in special populations such as pregnancy. This review examines the potential for TDM of newer AEDs such as eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, perampanel, pregabalin, rufinamide, retigabine, stiripentol, tiagabine, topiramate, vigabatrin, and zonisamide. We describe the relationships between serum drug concentration, clinical effect, and adverse drug reactions for each AED as well as the different analytical methods used for serum drug quantification. We discuss retrospective studies and prospective data on the serum drug concentration–efficacy of these drugs and present the pharmacokinetic parameters, oral bioavailability, reference concentration range, and active metabolites of newer AEDs. Limited data are available for recent AEDs, and we discuss the connection between drug concentrations in terms of clinical efficacy and nonresponse. Although we do not propose routine TDM, serum drug measurement can play a beneficial role in patient management and treatment individualization. Standardized studies designed to assess, in particular, concentration–efficacy–toxicity relationships for recent AEDs are urgently required.

Rapid advancement in drug discovery process is leading to a number of potential new drug candidates having excellent drug efficacy but limited aqueous solubility. By virtue of the submicron particle size and distinct physicochemical properties, nanosuspension has the potential ability to tackle many formulation and drug delivery issues typically associated with poorly water and lipid soluble drugs. Conventional size reduction equipment such as media mill and high-pressure homogenizers and formulation approaches such as precipitation, emulsion-solvent evaporation, solvent diffusion and microemulsion techniques can be successfully implemented to prepare and scale-up nanosuspensions. Maintaining the stability in solution as well as in solid state, resuspendability without aggregation are the key factors to be considered for the successful production and scale-up of nanosuspensions. Due to the considerable enhancement of bioavailability, adaptability for surface modification and mucoadhesion for drug targeting have significantly expanded the scope of this novel formulation strategy. The application of nanosuspensions in different drug delivery systems such as oral, ocular, brain, topical, buccal, nasal and transdermal routes are currently undergoing extensive research. Oral drug delivery of nanosuspension with receptor mediated endocytosis has the promising ability to resolve most permeability limited absorption and hepatic first-pass metabolism related issues adversely affecting bioavailability. Advancement of enabling technologies such as nanosuspension can solve many formulation challenges currently faced among protein and peptide-based pharmaceuticals.