Separuh hayat biologi

Separuh hayat biologi (juga separuh hayat penyingkiran dan separuh hayat farmakologi) ialah masa yang diambil bagi kepekatan bahan biologi (seperti ubat) berkurangan daripada kepekatan maksimum (C_maks) kepada separuh C_maks dalam plasma darah.^[1]^[2]^[3]^[4]^[5] Ia dilambangkan dengan singkatan $t_{\frac {1}{2}}$ .^[2]^[4]

Ini digunakan untuk mengukur penyingkiran perkara seperti metabolit, ubat-ubatan dan molekul isyarat daripada badan. Lazimnya, separuh hayat biologi merujuk kepada detoksifikasi semula jadi badan (pembersihan) melalui metabolisme hati dan melalui perkumuhan bahan yang diukur melalui buah pinggang dan usus. Konsep ini digunakan apabila kadar penyingkiran secara kasarnya bersifat eksponen.^{[Penjelasan diperlukan]}

Dalam konteks perubatan, separuh hayat secara eksplisit menerangkan masa yang diambil bagi kepekatan bahan dalam plasma darah untuk berkurang sebanyak separuh (separuh hayat plasma) daripada keadaan mantapnya apabila beredar dalam darah organisma. Pengukuran ini berguna dalam perubatan, farmakologi dan farmakokinetik kerana ia membantu menentukan berapa banyak ubat yang perlu diambil dan berapa kerap ia perlu diambil jika jumlah purata tertentu diperlukan secara berterusan. Sebaliknya, kestabilan bahan dalam plasma digambarkan sebagai kestabilan plasma. Ini penting untuk memastikan analisis yang tepat terhadap ubat dalam plasma dan dan penemuan dadah.

Hubungan antara separuh hayat biologi dan plasma sesuatu bahan boleh menjadi kompleks bergantung pada bahan berkenaan, disebabkan oleh faktor termasuk pengumpulan dalam tisu, pengikatan protein, metabolit aktif dan interaksi reseptor.^[6]

^ "Elimination Half-Life". Pharmacology in one semester. Diarkibkan daripada yang asal pada 22 October 2020. Dicapai pada 20 February 2020.
^ ^a ^b "Definition of Half-Life (t½)". AIDSinfo. 2020-02-19. Diarkibkan daripada yang asal pada 20 February 2020. Dicapai pada 2020-02-20.
^ Curry, Stephen H. (1993). "PHARMACOKINETICS OF ANTIPSYCHOTIC DRUGS". Antipsychotic Drugs and their Side-Effects. Elsevier. m/s. 127–144. doi:10.1016/b978-0-12-079035-7.50015-4. ISBN 978-0-12-079035-7. The elimination half-life measures the kinetics of loss of drug from the body as a whole once all distribution equilibria have been achieved.
^ ^a ^b Dasgupta, Amitava; Krasowski, Matthew D. (2020). "Pharmacokinetics and therapeutic drug monitoring". Therapeutic Drug Monitoring Data. Elsevier. m/s. 1–17. doi:10.1016/b978-0-12-815849-4.00001-3. ISBN 978-0-12-815849-4. The half-life of a drug is the time required for the serum concentration to be reduced by 50%. Once the half-life of the drug is known, the time required for clearance can be estimated. Approximately 97% of the drug is eliminated by 5 halflives, while ~99% is eliminated by 7 half-lives.
^ Toutain, P. L.; Bousquet-Melou, A. (2004). "Plasma terminal half-life" (PDF). Journal of Veterinary Pharmacology and Therapeutics. 27 (6): 427–439. doi:10.1111/j.1365-2885.2004.00600.x. PMID 15601438. Diarkibkan daripada yang asal (PDF) pada 2020-02-20. Following i.v. administration, the terminal half-life is the time required for plasma/blood concentration to decrease by 50% after pseudo-equilibrium of distribution has been reached; then, terminal half-life is computed when the decrease in drug plasma concentration is due only to drug elimination, and the term ‘elimination half-life’ is applicable. Therefore, it is not the time necessary for the amount of the administered drug to fall by one half.
^ Lin VW; Cardenas DD (2003). Spinal Cord Medicine. Demos Medical Publishing, LLC. m/s. 251. ISBN 1-888799-61-7.

[1] "Elimination Half-Life". Pharmacology in one semester. Diarkibkan daripada yang asal pada 22 October 2020. Dicapai pada 20 February 2020.

[AIDSinfo_2020-2] "Definition of Half-Life (t½)". AIDSinfo. 2020-02-19. Diarkibkan daripada yang asal pada 20 February 2020. Dicapai pada 2020-02-20.

[Curry_1993_pp._127–144-3] Curry, Stephen H. (1993). "PHARMACOKINETICS OF ANTIPSYCHOTIC DRUGS". Antipsychotic Drugs and their Side-Effects. Elsevier. m/s. 127–144. doi:10.1016/b978-0-12-079035-7.50015-4. ISBN 978-0-12-079035-7. The elimination half-life measures the kinetics of loss of drug from the body as a whole once all distribution equilibria have been achieved.

[Dasgupta_Krasowski_2020_pp._1–17-4] Dasgupta, Amitava; Krasowski, Matthew D. (2020). "Pharmacokinetics and therapeutic drug monitoring". Therapeutic Drug Monitoring Data. Elsevier. m/s. 1–17. doi:10.1016/b978-0-12-815849-4.00001-3. ISBN 978-0-12-815849-4. The half-life of a drug is the time required for the serum concentration to be reduced by 50%. Once the half-life of the drug is known, the time required for clearance can be estimated. Approximately 97% of the drug is eliminated by 5 halflives, while ~99% is eliminated by 7 half-lives.

[5] Toutain, P. L.; Bousquet-Melou, A. (2004). "Plasma terminal half-life" (PDF). Journal of Veterinary Pharmacology and Therapeutics. 27 (6): 427–439. doi:10.1111/j.1365-2885.2004.00600.x. PMID 15601438. Diarkibkan daripada yang asal (PDF) pada 2020-02-20. Following i.v. administration, the terminal half-life is the time required for plasma/blood concentration to decrease by 50% after pseudo-equilibrium of distribution has been reached; then, terminal half-life is computed when the decrease in drug plasma concentration is due only to drug elimination, and the term ‘elimination half-life’ is applicable. Therefore, it is not the time necessary for the amount of the administered drug to fall by one half.

[SCM-6] Lin VW; Cardenas DD (2003). Spinal Cord Medicine. Demos Medical Publishing, LLC. m/s. 251. ISBN 1-888799-61-7.

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Separuh hayat biologi

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