Review examines how well saliva tests may track antiviral drug levels
A systematic review found early signs for some antivirals, but overall feasibility is still uncertain.
High evidenceReviewSome caution advised
Medical disclaimer: This article summarizes research findings and is for informational purposes only. It is not medical advice.
Editorial illustration — not from the study.
Researchers asked whether saliva-based assays could be used for therapeutic drug monitoring (TDM) instead of full blood/plasma sampling. They searched MEDLINE, EMBASE, ClinicalTrials.gov, regulatory sources, and conference abstracts, and then assessed “feasibility” categories for specific antiviral drugs.
Overall, the review suggests that saliva may be useful for monitoring some antivirals (for example, valacyclovir and favipiravir were considered “possibly feasible”). For others, evidence was insufficient, predictions based on drug properties did not always match measurements, and factors beyond drug chemistry—such as drug transport—may affect how much drug appears in saliva.
What the review examined
The researchers investigated the feasibility of using saliva concentrations to perform antiviral therapeutic drug monitoring. They included primary studies that measured both saliva and plasma concentrations of antivirals used for prophylaxis or treatment of opportunistic viral infections in immunosuppressed patients, and they also compiled drug physicochemical properties from PubChem and DrugBank to predict salivary excretion. “Feasibility” was classified into ordered categories (likely, possible, unlikely, and “unclear” variants) based on available evidence and predictions.
What the review concluded
The review included nine studies. Valacyclovir and favipiravir were classified as “possibly feasible” for saliva-based TDM. Molnupiravir and oseltamivir were classified as “unclear but possible,” and nirmatrelvir was classified as “unclear but unlikely.” For other antivirals, the abstract states that no primary saliva-and-plasma studies were available; physicochemical profiles suggested saliva penetration might be feasible for some agents but limited for others. The abstract also reports that clinical study findings sometimes contradicted predictions based on drug properties, implying that additional factors (such as drug transporters) may influence salivary excretion. The authors describe the overall saliva-and-plasma data as scarce and inconsistent, leading them to conclude clinical utility is still not confirmed.
Where this may apply
These findings are most relevant to immunosuppressed patients who receive antiviral prophylaxis or treatment for opportunistic viral infections and where saliva-based drug monitoring is being considered as a less invasive alternative to blood or plasma testing. The review’s results do not establish clinical utility for practice, and they do not reliably apply to antivirals where saliva-and-plasma evidence was missing or where predictions conflicted with observed concentrations. This should be viewed as early, evidence-based feasibility assessment rather than guidance for patient care.
The significance
Therapeutic drug monitoring traditionally uses blood or plasma samples, which can be more invasive. If saliva could reliably reflect antiviral drug exposure, it could potentially make monitoring easier for patients who need prophylaxis or treatment—though this review emphasizes that current evidence is inconclusive for clinical utility. The findings here come from a synthesis of existing studies and drug-property predictions, not from definitive confirmation of how well saliva-based monitoring works in routine care.
Limitations & evidence assessment
Key limitations noted or implied by the abstract include: (1) saliva-and-plasma measurements were “scarce,” (2) data were “inconsistent,” and (3) for several antivirals, there were no primary studies reporting both saliva and plasma concentrations. Although the review used multiple data sources, it relies on limited and heterogeneous primary evidence. The feasibility categories also incorporate predictions from physicochemical properties, and the abstract says these predictions sometimes conflicted with observed data, suggesting that the evidence may be incomplete or influenced by unmeasured factors. The abstract does not provide details such as study designs, sample sizes, or specific assay methods, which limits how precisely readers can judge certainty.
Why this evidence level: Systematic review aggregating primary studies with explicit methodology.
Evidence levels are editorial estimates derived from study metadata — they are not clinical appraisals.
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