**12.1. Revision exercise 1**

**1.** Discuss the absorption of ά-D- Ribose-5-phosphate, given that the two ionizable hydroxyl groups of the monophosphate ester ribose have pKa values of 1.2. and 6.6. The fully protonated form of ά-D-ribose 5-phosphate has the following structure;

**i.** elimination rate constant (k)

**iii.** volume of distribution (Vd)

Solution*:*

Do = Co.Vd

**Solution**

= kxVxCss

= 56 mg/h

= 0.154 x 36.4 x 10

= (Ctox - Cther). V

**iii.** Maintenance dose

= (20 – 5) x 36.4 = 546 mg

**iv.** half-life of drug elimination (t ½).

**ii.** Co = Antilog of 1.3 = 10 1.3 = 20 mg/L

**i.** Drug clearance from the body

**iii.** Maintenance dose

**iv.** Maintenance interval

**v.** Initial loading dose

**ii.** Average rate of drug intake (Dosing rate)

**vi.** Loading dose at steady state concentration

**ii.** initial concentration of the drug in blood plasma (Co)

**i.** Slope = - k/2.303, therefore, k = -2.303x -0.08 = 0.184

**iii.** Volume of distribution (Vd) = Do/Co = 120/20 = 6 L

**iv.** The half-life of elimination t1/2 = 0.693/k = 0.693/0.184 = 3.7 hours.

Since t1/2 = 0.693/ k; k= 0.693/ t1/2 i.e. 0.693/4.5=0.154, and V= 0.56 x 65 = 36.4. **i.** Total drug clearance = kV = 0.154 x 36.4 = 5.6L/h = 93.3ml/min.

**ii.** Average rate of drug intake = rate elimination constant

that must be given to achieve a desired concentration can be determined from

4.5hrs, Vd = 0.56L/kg, Cmin the = 5mg/L, C tox = 20mg/L and Css = 10mg/L; calculate:-

Once the apparent volume of distribution is known for a particular drug the amount of drug

Introduction to Biochemical Pharmacology and Drug Discovery

http://dx.doi.org/10.5772/52014

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**Problem 4:** You have been given the following data based on a 65 kg patient; t1/2 of drug X =

**2.** Using specific examples of drugs, justify their various routes of administration.
