doses presentation.pdf
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doses, drugTRANSCRIPT
Farmasetika Dasar:
Dosis dan Obat Tak
Tercampurkan (OTT)
Tim Farmasetika Dasar
Fakultas Farmasi
UNPAD
2012
Tujuan Pembelajaran
Mahasiswa/i mampu:
1. Mengerti definisi dosis dan interaksi
obat/OTT
2. Menjelaskan jenis-jenis dosis
3. Memahami dosis pada kondisi tertentu
4. Menghitung dosis berdasarkan rumusnya
Dosis/Takaran •Ukuran/konsentrasi obat yang diharapkan dapat
mempunyai efek kerja/daya terapi pada orang dewasa
•Jumlah yang pasti dari suatu obat yang digunakan pada
satu kali kesempatan
Macam-macam Dosis • Dosis lazim/usual dose
• Dosis maksimal (TM)
• Dosis toksik
• Dosis letalis, LD50
• Dosis kuratif
• Dosis kombinasi (TM Berganda)
Faktor Penentuan Dosis
1. Umur
2. Berat Badan
3. Body Surface Area (BSA)
4. Jenis Kelamin
5. Status Patologi
6. Toleransi Obat
7. Waktu Pemakaian
8. Terapi dengan obat yang diberikan bersamaan
9. Bentuk Sediaan & Cara Pemakaian
Dokter
Perawat Apoteker
Terapi
Pasien
Pencegahan Error
Pembungkusan
Serbuk, kapsul, cairan, setengah padat
Ukuran sendok
• Sendok teh/cth (5ml)
• Sendok makan/C (15ml)
• Sendok bubur/Cp (10ml)
Pengukuran obat-dosis tepat
Ukuran yang dipakai
− Padatan : gram, miligram
− Cairan : cc, mL, L (BJ)
− Tube, pulv, syrup, Fl (fles), gtt, ampul
− Angka romawi : X, L, M
Timbangan
• Timbangan kasar (menimbang > 1 kg)
• Timbangan besar (timbangan gram, > 1 g)
• Timbangan kecil (>50 mg)
• Timbangan halus/timbangan mg (< 50 mg)
Penimbangan
− Untuk setengah padat : perkamen dilapisi parafin
− Untuk zat-zat kental : perkamen/cawan penguap
− Cairan : gelas ukur (cc), botol/cawan penguap (g)
Pengukuran obat-dosis tepat
Dosing in Children
• There are seven distinct age
groups that are associated with
different drug Cl and hence
dosing requirements.
• Note that four of these ages are
related to the paediatric age
group. This reflects that the
child is a continually changing
pharmacokinetic and
pharmacodynamic environment.
The younger the child, the
greater the rate of change.
• Dosing in children under 6
months of age is very
complicated a specialist advice
is usually needed.
• Body Surface Area (BSA)
calculation may be used when
an establish dosage has not
been determined by the drug
company, as with some
anticancer or specialized
drugs.
Dosage: the determination and regulation of the
size, frequency, and number of doses
Perhitungan TM untuk Anak-anak
• Rumus Young
(anak ≤ 8 tahun)
tahun, orang dewasa : 20 tahun)
• Rumus Dilling
(anak > 8 tahun)
• Rumus Talbot
(Berdasarkan luas permukaan tubuh)
(Lpb orang dewasa = 1,73 m2)
• Rumus Fried
(bayi ≤ 1 tahun,n= dalam bulan)
• Rumus Clark
(berdasarkan berat badan dalam pon)
• Rumus Evans
anak-anak
n = umur yang akan datang
untuk obat antiinfeksi.antibakteri
n = umur anak sekarang
untuk obat sensitif (opiat)
n = umur yang sudah lewat
..cont
Patients: 6 months–12 years
• Use surface area (SA) approach (Talbot)
1. Using nomograms :
Read SA from a nomogram
..cont
2. Without
nomograms
SA(m2):
4W(kg) + 7
W (kg) + 90
…cont
3. Using a calculator:
• In the absence of an estimate of surface area,
an adjusted body weight can be used as
follows:
• This equation is derived from the fact that
weight to the power of 0.7 (wt0.7) relates
better to surface area than to weight alone.
Dosing in Pregnancy
Pregnancy
Drug effects
…cont 1. Avoid all drugs if possible, including social drugs (e.g.
smoking, alcohol, caffeine)
2. Avoid drugs in the first trimester
3. Choose drugs of proven safety or least toxicity
4. Use short courses and the smallest doses
Dosing in Geriatric
Pada umumnya kecepatan absorbsi obat lebih lambat
pada lansia dari pada dewasa muda karena faktor-faktor
berikut:
1. Berkurangnya sekresi getah lambung sehingga
kecepatan disolusi sediaan tablet & kapsul menurun,
juga kadar ionisasi obat
2. Perubahan mukosa G.I. Dapat memperlambat transpor
aktif obat
3. Perubahan kecepatan pengosongan lambung, motilitas
usus, menurunnya aliran darah ke mesenterik
Membuat Serbuk Percobaan
Cara:
Semua zat dicampur (1/3-½ dari seluruh
campuran dalam resep), kemudian ditimbang 3
sendok rata dari serbuk percobaan, sehingga bisa
diketahui berat rata-rata 1 sendok. Bila sudah
diketahui berat 1 sendok, dapat diketahui
dosisnya, apakah melebihi DM atau tidak.
Cont’
Contoh : R/ Natrii Subcarbonas 70
Papaverini HCl 2 sekali 250 mg (papaverine HCl)
Magnesii Carbonas 7 sehari 1 gram
Elaeosacch. Anisi 10
Kaolin 7
Mds. 3.dd.cth.1
Pro. Tn. Anwar
Caranya :
Seluruh serbuk ditimbang, kecuali papaverini HCl, lalu ditimbang 3 sendok teh
rata (misal 1 sendok teh rata = 4 gram).
Seluruh campuran beratnya = 96 gram
Seluruh campuran ada = 96/4 = 24 sendok teh
1 sendok teh mengandung Papaverini HCl = 1/24 x 2 g
= 83,30 mg
Dosis sekali = 83,30/250 -------------------kurang dari DM
Dosis sehari = 3 x 83,30 -------------------- kurang dari DM
1000
Dosis maksimum sekali dan sehari tidak dilampaui, maka campuran serbuk dapat
dibuat dan diserahkan kepada pasien.
Contoh kasus 1
•How many milligrams of a drug are in two tablets if one tablet contains 5
mg of the drug?
State the problem as a proportion:
5 mg : 1 tablet :: X : 2 tablets
Remember the product of the means equals the product of the extremes:
1 tablet × X = 5 mg × 2 tablets
Solve for X. Divide each side of the equation by the known value, 1 tablet,
and cancel units that appear in both the numerator and denominator:
Contoh kasus 2
•A patient is scheduled to receive 0.05 mg levothyroxine P.O., but the only
drug on hand is in tablets that contain 0.025 mg each. How many tablets
should you give?
State the problem as a proportion:
0.025 mg : 1 tablet :: 0.05 mg : X
The product of the means equals the product of the extremes:
1 tablet × 0.05 mg = 0.025 mg × X
Solve for X by dividing each side of the equation by 0.025 mg and canceling
units that appear in both the numerator and denominator. Carefully check
the decimal placement.
Contoh kasus 3 •Your patient is receiving 500 mg of cefaclor in an oral suspension. The label reads
250 mg/5 ml, and the bottle contains 100 ml. How many milliliters of the drug
should you give?
1. Set up the first fraction with the known solution strength:
2. Set up the second fraction with the desired dose and the unknown number of
milliliters:
3. Put these numbers into a proportion:
4. Cross-multiply the fractions:
5. Solve for X by dividing both sides of the equation by 250 mg and canceling units
that appear in both the numerator and denominator
You'll need to administer 10 ml of cefaclor to the patient.
Contoh kasus 4 A drug order calls for 60 mEq potassium chloride liquid as a one-time dose, but the
only solution on hand contains 20 mEq/15 ml. How many tablespoons should you give
the patient?
1. Convert the milliliters to tablespoons by using a conversion table. You'll see that
15 ml equals 1 tbs; therefore, 20 mEq of the solution on hand equals 1 tbs.
2. Set up the first fraction with the amount desired over the amount you have:
3. Set up the second fraction with the unknown amount desired—X—in the
appropriate position:
4. Put these fractions into a proportion:
5. Cross-multiply the fractions:
6. Solve for X by dividing each side of the equation by 20 mEq and canceling units
that appear in both the numerator and denominator: X = 3 tbs
Contoh kasus 5
Contoh kasus 6
Contoh :
R/ Atropini Sulfas 0,5 mg
Bellad. Extr. 15 mg
Lactose q.s
m.f.Pulv.dtd. No X
S.t.dd.P.I
Pro Tn. Abd. Hamid
Menurut FI ed. III (1979) :
DM untuk Atropini Sulfas :
Sekali = 1 mg
Sehari = 3 mg
Jadi :
Persentase satu kali =
Persentase satu hari =
Contoh kasus 7
Contoh :
R/ Atropini Sulfas 0,5 mg
Bellad. Extr. 15 mg
Lactose q.s
m.f. syr 60ml
S.t.i.d. I cth
Pro: Hamid (5 thn)
Menurut FI ed. III (1979) :
DM untuk Atropini Sulfas :
Sekali = 1 mg
Sehari = 3 mg
DM Rumus
5 x 1 = 0,29 mg
5+12
Persentase satu kali
60ml/5ml=12 sendok
1 x 0,5 = 0,041 mg
12
0,041 x 100 = 14,1%/sendok
0,29
Persentase satu hari
0,041 x 3 x 100 = 13,9%/sendok
0,88
Contoh kasus 8
If the maintenance dose of a drug for 70 kg adult
is 100 mg per day, what is the appropriate dose
for a 15 kg child? Using surface area
SA = 0.62 m2: Using weight
Pustaka
1. Antoon, Melody C., Collins, Marissa R.K., Frazer, Christine.,
Greenawalt, Julia A., et al. 2007. Dosage Calculations: An
Incredibly Easy! Pocket Guide. 1st Edition. Philadephia:
Lippincott Williams & Wilkins.
2. Begg, Evan J. 2003. Instant Clinical Pharmacology. Blackwell
Publishing Ltd UK.
3. Langley, Christopher A and Belcher, Dawn. 2008. Pharmaceutical
Compounding and Dispensing. Chicago: Pharmaceutical Press.
4. Pickar, Gloria D. 2007. Dosage Calculations: A Ratio-Proportion
Approach. 2nd edition. New York: Thomson.
OTT
Drug interaction:
Both in vitro and in vivo physically and chemically
interaction
Any in vivo incompatibility in which clinical effects of
one drug may be desirably or undesirably altered by
the prior, concurrent, or subsequent administration of
the same or additional exogenous substances.
Interaction
Foods
Chemical
Physyical
Pharmacology
OTT
Pustaka
Martin, Eric W. 1971. dispensing Of Medication: Formerly husa’s
Pharmaceutical Dispensing. 7th edition. Pennsylvania: Mack
Publishing. 113-175
Terima Kasih The only source of knowledge is experience
-Albert Einstein-