The polar surface area (PSA) or topological polar surface area (TPSA) of a molecule is defined as the surface sum over all polar atoms or molecules, primarily oxygen and nitrogen, also including their attached hydrogen atoms.

Electrical potential surface of paracetamol showing polar areas in red and blue

PSA is a commonly used medicinal chemistry metric for the optimization of a drug's ability to permeate cells. Molecules with a polar surface area of greater than 140 angstroms squared (Å2) tend to be poor at permeating cell membranes.[1] For molecules to penetrate the blood–brain barrier (and thus act on receptors in the central nervous system), a PSA less than 90 Å2 is usually needed.[2]

TPSA is a valuable tool in drug discovery and development. By analyzing a drug candidate's TPSA, scientists can predict its potential for oral bioavailability and ability to reach target sites within the body. This prediction hinges on a drug's ability to permeate biological barriers.

Permeating these barriers, such as the Blood-Brain Barrier (BBB), the Placental Barrier (PB), and the Blood-Mammary Barrier (BM), is crucial for many drugs to reach their intended targets.

The BBB, for example, protects the brain from harmful substances. Drugs with a lower TPSA (generally below 90 Ų) tend to permeate the BBB more easily, allowing them to reach the brain and exert their therapeutic effects (Shityakov et al[3]., 2013).

Similarly, for drugs intended to treat the fetus, a lower TPSA (below 60 Ų) is preferred to ensure they can pass through the placenta (Augustiño-Roubina[4] et al., 2019).

Breastfeeding mothers also need consideration. Here, an optimal TPSA for a drug is around 60-80 Ų to allow it to reach the breast tissue for milk production, while drugs exceeding 90 Ų are less likely to permeate the Blood-Mammary Barrier.[5]

See also

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References

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  1. ^ Pajouhesh H, Lenz GR (Oct 2005). "Medicinal Chemical Properties of Successful Central Nervous System Drugs". NeuroRx. 2 (4): 541–553. doi:10.1602/neurorx.2.4.541. PMC 1201314. PMID 16489364.
  2. ^ Hitchcock SA, Pennington LD (May 2006). "Structure - Brain Exposure Relationships". J. Med. Chem. 49 (26): 7559–7583. doi:10.1021/jm060642i. PMID 17181137.
  3. ^ Shityakov, Sergey; Neuhaus, Winfried; Dandekar, Thomas; Förster, Carola (2013). "Analysing molecular polar surface descriptors to predict blood-brain barrier permeation". International Journal of Computational Biology and Drug Design. 6 (1–2): 146–156. doi:10.1504/IJCBDD.2013.052195. ISSN 1756-0756. PMID 23428480.
  4. ^ Hester, Gabrielle; Lang, Tom; Madsen, Laura; Tambyraja, Rabindra; Zenker, Paul (January 2019). "Timely Data for Targeted Quality Improvement Interventions: Use of a Visual Analytics Dashboard for Bronchiolitis". Applied Clinical Informatics. 10 (1): 168–174. doi:10.1055/s-0039-1679868. ISSN 1869-0327. PMC 6402943. PMID 30841007.
  5. ^ "Δραστική: PARACETAMOL". farmako.net. Retrieved 2024-04-10.

Literature

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