- DDi vdi mot sDthuDc chi sau khi chuyen hoa mdi cotac dung hoac tang dQc tinh thi cam ling enzym lam tang tac dung hoac tang dQc tinh cua thuoc.
3. cAe YEU TO ANH HU'dNG DEN TAe DVNG eVA THuoe
3.2.4. Trgng thai b~nh ly
Ngoai cac ye'u to vg gioi tinh, lua tu6i, tac d\lng cua thuoc con bi anh htidng bdi tr~ng thai b~nh IY. Noi chung cd th~ om nh~y cam voi thuoc hon co th~ Ianh. M(>tso thuoc chi co tac d\lng ro r~t d cd th~ om. Vi d\l cac thuoc chua hen ph fin Ion chi co tac d\lng gian phe' quan khi phe' quan bi co th&t; cac thuoc h~ sOt tac d\lng ro r~t khi tang than nhi~t v.v ... 0 nhung ngtidi viem gan, xd gan, viem th~n khong nhung giam chuy~n hoa thuoc, giam protein huye't ttidng
(tang thuoc (j dang tu do), tang tll2 d~n den tang sinh kha dung cua thuoc, d~ gay ng9 d9c. Vi du tac dung chong dong mau cua cac thuoc chong dong d~n chat coumarin manh hen (j nhiing nguoi bi suy gan; ligu gay me cua thiopental (j nhfing nguoi suy than chi bang 1I21igu dung cho nguoi binh thuong.
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4. PHAN UNG BAT LQI eUA THUOe (Adverse drug reaction- ADR)
4.1.Dinh nghia
"ThuO'Cdung trong nganh y te la nhfing chat co tac dung duoc ly nham chua benh, phong benh, phuc h6i hoac dieu chinh chirc nang cua co th~, lam. giam trieu chung benh, chan doan benh, phuc h6i hoac nang cao sire khoe cho con nguoi ...". Tuy nhien, thuoc cling duoc coi la "con dao hai ludi" vi co th~ gay ra cac phan ung co hai (jnhieu muc d9, tham chi til vong k~ ca dung dung lieu, dung quy dinh, cac phan ung nhu vay dUQcgQila tac d\lng bat lQi.
T6 chuc Y te The gioi (2002) d11dua ra dinh nghia ve phan ung bat lQiclla thuO'c(ADR)nhu sau:
"Phan ung bat lc;Jicua thuoc la m{}t phan ltng d{}c hg,i, khong dUrJcdinh trudc va xuat hi~n dliiu thudng dung cho ngudi de'phong b~nh, chan doan ho{ic chfta b~nh ho{ic lam thay ddi m{}t chuc nang sinh ly"'.
Dinh nghia nay khong bao g6m nhung ph an ung do dung sai thuO'c,dung sai lieu, dung lieu cao co chll dinh hol).cvo tinh. Trong dinh nghia nay, yeu to' dap ung ca th~ la rat quan trQng.
Co nhieu trudng hQp tai bien ph at sinh trong qua trinh dieu tri ma nguyen nhan chua duQcxac dinh. Nguyen nhan trong nhung trudng hQp nay khong chi do thuO'cgay ra ma co th~ do cac yeu to' khac nhu sl,itien tri~n nl).ngthem clla b~nh hol).cdo m9t b~nh khac phat sinh. Nhung trudng hQp nhu v~y gQila bien cO'bat lQiclla thuO'C(Adverse drug experiencel Adverse drug event- ADE).
4.2. Phan lo~i ADR
4.2.1. Phan logi theo tiln suat gijp
- Thudng gl).p ADR> 11100
- ft gl).p - Hiem gl).p
11100<ADR < 1/100
ADR <111000
4.2.2. Phan logi thea mite d{j nijng ella b~nh do ADR gay ra
- Nh~: khong clln dieu tri, khong cftn giai d9c va thdi gian n&m vi~n khong keo dai.
- Trung binh: clin co thay d6i trong dieu tri, clin dieu tri dl).chi~u hol).ckeo dai thdi gian n&mvi~n it nhat 1 ngay.
- Nl).ng:co th~ de dQa tinh m~ng, gay b~nh t~t lau dai hol).cclln cham soc tich cl,ic.
4.2.3. Phan loo.i theo typ
• Typ A
Cac ADR typ A co cac d~c di~m sau:
- Tien luong duoc (du dean truce dude).
- Thuong phu thuoc ligu dung (do do cac ADR typ A thuong g~p d6i vdi cac thu6c co pham vi dieu tri hep),
- La tac dung duoc ly qua muc hoac la mQt bi~u hien cua tac dung duoc ly d
mot vi tri khac,
Sau day la mot so'vi du cho cac ADR typ A:
- La tac dung dieu tri nhung cuong dQ vuot qua rmrc cftn thiet nhu: chay mau khi dung thuoc chong dong mau, ha duong huyet khi dung thu6c dieu tri dai thao duong, tut huyetap khi dung thu6c digu tri tang huyetap ... - La tac dung dieu tri nhung d vi tri hoac co quan khac hoac do tinh chat
khong chon IQctren cac khang th\l th~, vi d\l: phan ung ngo~i thap voi cac thu6c khang th\l th~ dopaminergic, tac d\lng gay ung thu ch~m clla cac thu6c gay dQcte bao va estrogen ho~c tac d\mg tren h~ tieu hoa clla cac chat uc che cyclooxygenase khong chQn IQc(cac NSAID).
- La tac d\lng duqc ly khac clla thu6c nhung khong phai la tac d\lng digu tri, vi d\l: cac thu6c ch6ng trftm cam 3 vong th~ hi~n ca tac d\lng khang th\l th~ muscarinic, khong co vai tro trong digu tri ch6ng trftm cam thudng gay kho mi~ng, giam thi h;iC ... ho~c tac d\lng khang androgen clla cimetidin .
• TypB
Cac ADR typ B co cac d~c di~m sau: - Thudng khong tien luqng duqc.
- Khong lien quan den cac d~c tinh duqc ly da biet clla thu6c.
- Thudng co lien quan Wi cac yeu to' di truygn ho~c mi~n dich, u buou ho~c cac yeu to' gay quai thai.
Di ung thu6c la mQt vi d\l di~n hinh cho ADR typ B vi khong tien luqng duqc va khong ph\l thuQc ligu dung. Di (tng thu6c duqc giai thich hoan toan thong qua cd che mi~n dich di ung, khong lien quan den cac tac d\lng duqc ly clla thu6c. Bi~u hi~n lam sang clla di ung thu6c rat da d~ng, cac cd quan bi t6n thudng co th~ co th~ la da, gan, th~n, dudng tieu hoa ho~c toan than; muc dQ nghiem trQngtit nh~ (ban da, ngua ...) den rat n~ng, th~m chi gay ttt vong cho b~nh nhan nhu s6c phim v~, h9i chung Lyell, Stevens- Johnson ... Tuy khong tien luqng duqc nhung co th~ h~n che sl;i xuat hi~n clla di ung thu5c neu cac nhan vien y te co bi~n phap theo d6i ch~t che va phat hi~n som.