Pharmaceutical calculation for farmasi

1. Pharmaceutical
calculation
PSPA UHAMKA-ANGKATAN 38
AGUSTUS 2022

2. Perhitungan Farmasetika (Pharmaceutical Calculation)
• Pelayanan Obat di Apotek dan Rumahsakit//Drug Compounding
Takaran/Dosis
• Perhitungan Kadar Obat>>industri

3. ➢Materi perhitungan meliputi:
• Aligasi
• Perubahan kekuatan produk
• Triturasi
➢Sub materi:
• Kekuatan Produk dalam Peracikan Farmasi
• Hubungan Antara Kekuatan dan Jumlah Total
• Pengenceran dan Konsentrasi Cairan
• Penguatan Produk Farmasi, Larutan Stok
• Pengenceran Alkohol, Pengenceran Asam
• Pengenceran dan Fortifikasi Padatan dan Semipadat

4. Aligasi
✓Alligation is an arithmetic method of solving problems relating mixtures
of components of different strengths
✓Alligation is a rule which is used to solve the problems related to mixture
and its ingredient
1. alligation medial :
➢used to determine the strength of a common ingredient in a mixture of two or more
preparations. For example, if a pharmacist mixed together known volumes of two or
more solutions containing known amounts of a common ingredient, the strength of that
ingredient in the resulting mixture can be determined by this method.

5. 2. alligation alternate.
➢used to determine the proportion or quantities of two or more components to combine
in order to prepare a mixture of a desired strength. For example, if a pharmacist wished
to prepare a solution of a specified strength by combining two or more other solutions
of differing concentrations of the same ingredient, the proportion or volumes of each
solution to use may be determined by alligation alternate.

6. • https://www.youtube.com/watch?v=8l6l30-8Ffo&t=204s

7. Alligation Medial
• method by which the ‘‘weighted average’’ percentage strength of a mixture of two or
more substances of known quantity and concentration may be easily calculated.
• By this method, the percentage strength of each component, expressed as a decimal
fraction, is multiplied by its corresponding quantity; then the sum of the products is
divided by the total quantity of the mixture; and the resultant decimal fraction is
multiplied by 100 to give the percentage strength of the mixture.
• Of course, the quantities must be expressed in a common denomination, whether of
weight or volume.

8. • What is the percentage strength (v/v) of alcohol in a mixture of 3000 mL of 40% v/v alcohol, 1000
mL of 60% v/v alcohol, and 1000 mL of 70% v/v alcohol? Assume no contraction of volume after
mixing.
• What is the percentage of zinc oxide in an ointment prepared by mixing 200 g of 10% ointment, 50
g of 20% ointment, and 100 g of 5% ointment?
0.40 x 3000 mL = 1200 mL
0.60 x 1000 mL = 600 mL
0.70 x 1000 mL = 700 mL
Totals: 5000 mL--- 2500 mL
2500 (mL) : 5000 (mL) = 0.50 x 100 = 50%

9. Alligation Alternate
• method by which we may calculate the number of parts of two or more components of
a given strength when they are to be mixed to prepare a mixture of desired strength.
• A final proportion permits us to translate relative parts to any specific denomination.
• The strength of a mixture must lie somewhere between the strengths of its
components; that is, the mixture must be somewhat stronger than its weakest
component and somewhat weaker than its strongest.
• As indicated previously, the strength of the mixture is always a ‘‘weighted’’ average; that
is, it lies nearer to that of its weaker or stronger components depending on the relative
amounts involved.

10. 1
2
In what proportion should alcohols of 95% and 50% strengths be mixed to make 70% alcohol?

11. In what proportion should 20% benzocaine ointment be mixed with an ointment base to
produce a 2.5% benzocaine ointment

12. Perubahan Kekuatan Produk
➢The strength of a pharmaceutical preparation may be increased or decreased by
changing the proportion of active ingredient to the whole.
➢A preparation may be strengthened or made more concentrated by the addition of
active ingredient, by admixture with a like preparation of greater strength, or through
the evaporation of its vehicle, if liquid.
➢The strength of a preparation may be decreased or diluted by the addition of diluent or
by admixture with a like preparation of lesser strength

13. • Q1 x C1 = Q2 x C2
• V1 x C1=V2 x C2
500 mL larutan (15% v/v) diencerkan hingga 1,5 L
Berapa kekuatan larutan (% v/v)?
500 x 15% = 1500 x C2 (%) >> 5%

14. 1:20 = 5%
50 x 5 (%) = 1000 x C2 (%) >> C2 = 0,25 % >> 1:400
50 mL Larutan 1:20 w/v diencerkan hingga 1 L
Tentukan kekuatan larutan dalam rasio w/v…..
Larutan sirup mengandung 65% w/v sukrosa menguap hingga
volumenya menjadi 85%. Berapa % (w/v) kandungan sukrosa dalam
larutan??
Dianggap larutan vol.awal 100 mL >> 85% = 85 mL
Dalam 100mL ada 65% sukrosa>> dalam 85 mL???
V1 x C1 = V2 x C2 >> 100 x 65 (%) = 85 x C2 (%) >> 76,47 %

15. SOAL
Kekuatan produk
1. Apoteker menerima resep suspensi antibiotik 100 mL dengan kandungan zat aktif 300mg/5mL. Di
apotek tersedia suspense 250mg/5mL dan tablet 250 mg.
• Berapa jumlah tablet yang dibutuhkan untuk membuat suspense yang diminta?
• Kandungan zat dalam suspensi yang tersedia:
100 mL x (250 mg/5 mL) = 5000 mg
• Suspensi yang diminta dari resep: 100 mL x (300 mg/5 mL) = 6000 mg
• Jumlah zat aktif = 6000 – 5000 = 1000 mg
• Tablet yang diperlukan = 1000 mg x (1 tablet/250 mg) = 4 tablet

16. Pengenceran/ Drug Dilutions
➢ Konsentrasi (jumlah atau
volume)

17. • Konsentrasi:
• Pengenceran (Dilutions):

21. PENGENCERAN >> LARUTAN INDUK
• Berapa volume larutan induk (1:400 w/v) yang digunakan untuk membuat 4 L
larutan dengan kekuatan 1:2000 w/v
4 L = 4000 mL >> 1 : 400 = 0,25%
1 : 2000 = 0,05%
V1 x C1 = V2 x C2 >> V1 x 0,25 (%) = 4000 x 0,05 (%)
V1 = 800 mL

22. SOAL
• Berapa volume (mL) larutan Natrium hipoklorit (1:16) yang diperlukan untuk menyiapkan
5L larutan Na.Hipoklorit 0,5%?
1:16 = 6,25%
V1 x C1 = V2 x C2
• Resep berikut:
R/Fenilefrin HCl 0,25% (larutan induk tersedia 1:50)
Aquadest ad 30 mL
s.ue
berapa volume (mL) larutan induk yang diambil untuk resep tersebut?
•

23. • Berapa volume (mL) air ditambahkan ke dalam 300 mL larutan benzalkonium
klorida(1:750 b/v) menjadi larutan dengan konsentrasi 1:2500 b/v?
1:2500 = 0,04% …. 1:750 = 0,133%
V1 x C1 = V2 x C2

24. PENGENCERAN ALKOHOL
• Pencampuran air dan alkohol >> terjadi tarikan fisika
→volume yang dihasilkan campuran menjadi lebih kecil dari toal individu masing-
masing cairan
• Preparasi larutan alkohol (v/v) >> ditentukan jumlah alkohol dan air yang
digunakan (q.s)
→tarikan fisik cairan tidak mempengaruhi berat komponen, maka berat air (b) =
volume (v) diperlukan untuk mengencerkan alkohol (b/b)
Berapa air yang harus dicampurkan dengan 5L alkohol 85% v/v untuk membuat
alkohol 50% v/v ….

25. PENGENCERAN ASAM
• Kekuatan asam (pekat) yang tidak diencerkan, dinyatakan sebagai persentase b/b
• Contoh: HCl → megandung tidak kurang 36,5% dan tidak lebih 38,0% berat
HCl
• Kekuatan asam dengan pengenceran >> dinyatakan sebagai % b/v
• Contoh: HCl(encer) dalam 100mL mengandung tidak kurang 9,5 gram dan
tidak lebih 10,5 gram HCl
• → dipertimbangkan nilai berat jenis asam pekat dalam menghitung volume yang
diperlukan dalam menyiapkan larutan asam encer

26. soal
• Berapa volume (mL) larutan HCL 37% b/b (BJ 1,20) yang diperlukan untuk
membuat 1 L larutan asam encer 10% b/v?
HCl 10% b/v 1000 mL = 1000 g x 0,10 = 100 g HCl (100%) dalam 1000 mL
V1 x C1 = V2 x C2
V1 x 37 (%) = 100 g x 100 (%) → V1 = 270 g (=mL) ……. BJ 1,20 (g/mL)
V1 = 270/1,20 = 225 mL

27. Pengenceran dan Fortifikasi Solid dan Semisolid
➢ The dilution of solids in pharmacy occurs when there is need to achieve a lower concentration of an active
component in a more concentrated preparation (e.g., a powdered vegetable drug).
Triturasi
➢ Dilutions of potent medicinal substances Prepared by diluting one part by weight of the finelypowdered
lactose10% or 1:10 (w/w) mixtures
• They are, therefore, 10% or 110 w/w mixtures.
• These dilutions offer a means of obtaining conveniently and accurately small quantities of potent drugs for
compounding purposes. Although no longer official as such, triturations exemplify a method for the
calculation and use of dilutions of solid medicinal substances in compounding and manufacturing procedures.
• A modern-day example of a trituration is the product Trituration of MUSTARGEN (mechlorethamine hydrochloride for
injection), in which 10 mg of the highly toxic drug is triturated with 90 mg of sodium chloride. The trituration is
dissolved in sterile water for injection or in sodium chloride injection prior to administration

28. Pengenceran sediaan (solid dan semisolid)
• Pengenceran dalam sediaan diperlukan :
→Zat aktif dengan konsentrasi yang lebih rendah dalam sediaan
• Pengurangan atau peningkatan kekuatan/dosis dibutuhkan untuk pasien dengan
kondisi tertentu
Jika 30 g salep hidrokortison (1%) diencerkan dalam 12 g vaselin, berapa konsentrasi
hidrokostison dalam campuran?
Kadar 1% x 30 g = 0,3 g hirokortison
Berat total sediaan = 30 g + 12 g = 42 g >> konsentrasi akhir = 0,3 g/42 g x 100% = 0,71%

29. soal
• Apoteker diminta menyiapkan salep zink oksida 20% dari salep yang sudah
tersedia, yaitu 3200 g kadar 5%. Berapa jumlah zink oksida yang dibutuhkan?
Tahap 1: salep yang tersedia→ 5% x 3200 g = 160 g zat aktif dalam sediaan
3200 g – 160 g = 3040 g (berat basis)
Tahap 2: permintaan sediaan kadar zat aktif 20% → basis 80%
Q1 x C1 = Q2 x C2
Q1 x 80(%) = 3040 x 20 (%)
Q1 = 760 g → zat aktif total dalam salep 20%
Tahap 3: zink oksida yang sudah ada (dalam salep 5%) = 160 g
Jumlah yang diperlukan = 760 g – 160 g = 600 g

30. • Contoh soal Triturasi
1. How many grams of a 1:10 trituration are required to obtain 25 mg of drug?
2. How many mg of a 1:10 dilution of colchicine should be used by a
manufacturing pharmacist in preparing 100 capsules for a clinical drug study
if each capsule is to contain 5 mg of colchicine

31. LATIHAN SOAL