3.3. Thuoc uc che gUm tiep h~ adrenergic
3.3.1. Reserpin
Duoc d9ng hoc
Hap thu duoc qua duong u5ng va tiern. Tac dung xuat hien cham va keo dai (sau khi uong 2- 3 ngay mdi xuat hien tac dung va keo dai tdi 14 ngay sau khi ngung thuoc). Dang tiem thuoc xuflt hien tac dung nhanh, bAt dau 1- 2 gio va het tac dung sau 6- 12 gio. Reserpin qua duoc nhau thai va sua me. Thu5c duoc chuyen h6a thanh dang khong hoat tinh va thai tru chu yeu qua phan,
Ttic dung va coche'
Reserpin uc che sinh tang hop va du tru catecholamin, tang giai ph6ng catecholamin, ngan can thu h6i catecholamin v~ ngon sci, gay c~n ki~t catecholamin dca trung liong va ngo~i vi, do d6 uc che th~n kinh trung liong va lam giam chuc nang giao cam.
- Tren th~n kinh trung liong va tam th~n: Reserpin c6 tac d\lng an th~n, giam cang th&ng,h6i h9P, 10 au, t~o tr~ng thai binh than, thd0voi ngo~icanh. - Tren th~n kinh giao cam:
Reserpin gian tiep uc che a va ~- adrenergic gay tac d\lng tren ca.cco quan va tuyen nhli sau: gay co d6ng ttl, giam chuc nang tu~n hoan nhli giam nhip tim, giam suc co b6p co tim, gian m~ch va h~ huyet ap (tac d\lng h~ huyet ap ch~m nhling keo dai), tang co b6p co tron, tang tiet dich, giam chuy~n h6a, UC che FSH va LH, r5i lo~n bai tiet sua, giu nlioc.
Chi dinh
Tang huyet ap.
Lo~n nhip tim: ngo~i tam thu, nhip nhanh thflt, rung tam thflt. R5i lo~n tam th~n th~ hling cam.
B~nh Raynaud.
Tac dung khong mong muon
Cac tac d\lng khong mong mu5n thlidng lien quan den tac d\lng clidng giao cam va uc che th~n kinh trung liong cua thu5c.
Tren th~n kinh: thu5c gay bu6n ngu, hoa mAt, ch6ng m?t, dau d~u, tr~m cam, giam kha nang tli duy.
Tren tieu h6a: ga.y ro'i lo~n tieu h6a nhu chan an, bu6n non, non, tieu chay, loet d~ day- ta trang.
Tren ho hflp: gay sung huyet niem m~c mfli.
Khi dung li~u cao, keo dai gay h9i chung Parkinson, tang tiet sua, r5i lo~n kinh nguy~td ph\l nu va chung vu to, giam tinh d\lcdnam gioi.
Tuang tcic thuoc
Khong dung dong thoi vdi cac thuoc sau:
Voi digitalis vi lam tang tac dung cham nhip tim. Vdi IMAO vi d~ gay con tang huyetap kich phat.
Vdi thuoc uc che than kinh trung uong vi gay tang tac dung uc che than kinh trung uong.
cn«phdm va lieu dung
- Che' pham: vien nen 0,1; 0,25; 0,5 va 1mg. Ong tiem 1mg.
- Lieu dung: Nguoi ldn: 0,1- 0,25mg/ 24h. Tre em: 5- 20~g/ kg/ 24h.
3.3.2. Guanethidin (lsmeline)
Guanethidin co tac dung tuong tu reserpin, gay uc che tim va ha huyetap nhung khong co tac dung tren than kinh trung uong, 'I'ac dung cham va keo dai. 4. THunc KiCH THicH H~ CHOLINERGIC (Thu6c Cllong ph6 giao cam)
4.1. Thuoc kich thich tr1;ictiep receptor M va N
4.1.1. Acetylcholin Ngu6n goc
Trong co th~, acetylcholin duoc tiet ra tu ngon soi trudc hach giao cam va pho giao cam, sau hach pho giao cam, ngon soi den tuy thuong than, ban van d9ng co xuong va th~n kinh trung udng.
Acetylcholin dung trong y h9Cla lo:;tit6ng hQp.
Dttflc d9ng h9c
Acetylcholin bi phan huy d dUdng tieu hoa nen khong dung dUdng uong. Thu5c hap thu nhanh qua dUdng tiem blip va tiem duoi da. Khong dUQctiem tinh m:;tchvi hap thu qua nhanh, tac d\lng xay ra nhanh va m:;tnh d~ gay tai bien h:;thuyet ap d9t ng9t, roi lo:;tnnhip tim (cac d§.n xuat khac cua cholin ben vflng hdn co th~ uong dUQc).
Acetylcholin co chua nhom amin b~c 4 nen rat kho tham qua hang rao sinh hQc, khong VaGdUQcte bao th~n kinh, nhung co th~ VaGcac t6 chuc khac cua cd th~. Nang d9 thuoc trong huyet tUdng IOnhdn trong ta chuc.
Trong cd th~ acetylcholin nhanh chong bi chuy~n hoa bdi cholinesterase t:;tothanh cholin va acid acetic. Thai tru m9t ph~n qua nuoc ti~u.
Tcic dlfng
Acetylcholin kich thich tn;ic tiep tren h~ M va N. Tac d\lng tren h~ M chiem uu the hdn nen thl,ic te tac d\lng cua acetylcholin bi~u hi~n la cUdng pho giao cam.