As mentioned in the comment to the question, without empirical data, any comparison would be speculative and could potentially lead to incorrect dosing, reduced efficacy, or increased risk of adverse effects. To comprehensively compare the efficacy and bioequivalence of rectal diazepam and buccal midazolam, empirical data are essential.
I would like to know in general what is an appropriate method for making such comparisons
Pharmacokinetic and Pharmacodynamic Studies:
To determine if one dose of a medication is equivalent to another, especially when administered via different routes, studies that measure the pharmacokinetic (PK) and pharmacodynamic (PD) profiles are necessary. PK studies would provide data on absorption, distribution, metabolism, and excretion, while PD studies would give insight into the drug’s effects and mechanisms of action at the target sites.
Bioequivalence and Bioavailability Studies: Bioequivalence studies involve comparing the bioavailability of two drugs or two different formulations of the same drug. These studies typically measure the time to reach maximum concentration (Tmax), maximum concentration (Cmax), and the area under the concentration-time curve (AUC) to determine if the two are equivalent.
Dose-Response Relationship: Empirical data can help define the dose-response relationship for each drug. This relationship can differ between drugs (and patients - see below) and can be influenced by the route of administration, which is particularly important in your case. Empirical data would allow for the assessment of the therapeutic window of each drug.
Clinical Trials: Randomised controlled trials comparing the two medications in question would provide evidence of efficacy, safety, and side effects. This information is critical when determining which drug to use in a clinical setting, as it provides direct evidence of how the drugs perform in patients.
Safety and Efficacy Profiles: Because drugs can have different safety profiles depending on the route of administration (for example, due to differences in metabolism), empirical data on adverse effects are crucial for making an informd comparison.
Interindividual Variability: There is considerable variability in how different individuals metabolise and respond to the drugs. Empirical data from a population can help establish a range of expected responses and identify any outliers or special considerations.