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Formulating Medicine And Compounds > LAURA > Flashcards

LAURA Flashcards

1
Q

Initiation phase

A

A new drug is formed. Drugs can be made naturally ; so you extract it, purify it and use bio technology. Or drugs can be made be made through chemical synthesis

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2
Q

Pre formulation

A

To create the optimum conditions you have to look at the characteristics of the medication being formed such as solubility and particle size

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3
Q

Formulation

A

Figure out what form the medication is best in. E.g. oral suspension, tablets, capsules or injections

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4
Q

Clinical trials

A

Phase l : in humans to test safety, pharmacodynamics and pharmacokinetics
Phase ll : in patients to test efficacy and dose ranging
Phase lll : in larger amount of people to confirm efficacy and patient safety / tolerance

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5
Q

Marketing Drug

A

How to market drug and whether it will be sold as a POM, GSL or P

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6
Q

Acid and Base

A

Acid contains a lot of H± ions
Base contains little H± ions, a soluble base is an alkali

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7
Q

Bronsted and Acid pairs

A

When a Bronsted base or acid donates or releases a proton then it becomes a conjugate base or acid

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8
Q

Weak and strong acids

A

They completely dissociate into ions

Weak acid (reversible reaction) HA <->H+ A-

Strong acid (forward reaction) HA —> H+ A-

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9
Q

What makes an acid strong

A

Solvent effect
Strength
Nature of parent molecule
Energetic stability

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10
Q

Monoprotic, diprotic, polyprotic

A

Monoprotic means one proton is lost per molecule
Diprotic means two protons are lost per molecule
Polyprotic multiple protons are lost per molecule

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11
Q

Thermodynamics and Kinetics

A

Kinetics is rate of reactions and thermodynamics is the energy involved with the process

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12
Q

Zero Order Reactions

A

The rate of reaction is constant and doesn’t depend on the concentration of reactant A. The rate is constant

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13
Q

First order reactions

A

Rate of reaction depends on the concentration of reactant A

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14
Q

Second order reactions

A

The rate of reaction depends on the concentration of reactants A and B or the square of one reactant
A+B——->C

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15
Q

4 factors that affect rate of reactant

A

Stirring, particle size, concentration of a reactant, temperature

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16
Q

What are catalysts?

A

They speed up the rate of reaction by offering an alternative activation energy pathway. (make sure you know the diagram)

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17
Q

First law of thermodynamics (enthalpy) ΔH

A

Change must be measured ΔH- is the amount of heat energy given out or given in as a reaction reaches a particular temperature
Can be endothermic or exothermic
Exothermic is negative
Endothermic is positive

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18
Q

Mean bond enthalpy

A

Enthalpy can be predicted from considering the mean bond enthalpies associated with the reaction:
* Mean Bond Enthalpy (kJmol-1)
* C-H 412
* O=O 497
* C=O 743
* H-O 464
* Enthalpy change to break all the bonds in a molecule of methane:
* 4 x 412 = 1648 kJ/mol

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19
Q

Entropy (ΔS):

A

Refers to order or disorder in a system
High entropy means high disorder
You can increase entropy by heating or providing more space for molecules and entropy for a liquid is higher than solid or gas.

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20
Q

Gibbs free energy ΔG

A

• At constant temperature and pressure (i.e. enthalpy is zero):
ΔG = - T ΔS
• Therefore it is another way of expressing entropy at a constant temperature

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21
Q

Van hoff equation

A

Used to estimate enthalpy and entropy of a chemical reaction. Done by measuring the equilibrium constant Keq at different temperatures the enthalpy and entropy of a reaction can easily be obtained • ΔH = - R x slope
• ΔS = R x intercept

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22
Q

Define AH, AS and AG and how they are related.

A

AH Enthalpy heat change, positive = endothermic, negative =
exothermic
AS Order, at T=0 S =0 so usually a reaction increases the disorder. Such as heating a solid to melt increases disorder, AG Gibbs free energy, the overall energy change for a reaction, AG
= AH - T AS (T is in Kelvin)

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23
Q

What does equilibrium mean

A

Chemical reaction that occurs in equal in forward and reverse reactions so concentrations do not change with time

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24
Q

Factors that affect equilibrium position

A

Temperature, pressure and concentration

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25
Q

Equilibrium constant

A

When a reversible reaction reaches a dynamic equilibrium the concentration of reactant a and products remain constant
You can work this out as well

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26
Q

Le Châtelier’s principle:

A

If you change the conditions of a reaction it affects the equilibrium position

Le Chatelier’s Principle states that if you disturb a system at equilibrium, the system will adjust itself to counteract that disturbance and try to restore a new equilibrium.

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27
Q

Change in pressure

A

If you increase the pressure, the system will try to reduce it by being pushed to the side with the least number of moles
A catalyst does not change the position of equilibrium just the rate of equilibrium that is achieved is changed

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28
Q

Equilibria for WEAK ACIDS

A

Keq becomes ka
Strong acid means ore hydrogen ions- gives a larger ka
Weaker acids means less hydrogen ions which give smaller ka

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29
Q

Polyprotic acids

A

Has many pKa values as many protons are lost per molecule.

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30
Q

Ionisation

A

Ionisation is the process where a molecule splits into ions . For a drug to dissolve in your body it needs to ionise

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31
Q

PKa

A

Measure of the strength of acid. It’s the ph at which half of the drug molecules are ionised and half are not. The lower the pKa the stronger the acid which means it ionises more easily

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32
Q

PKa and ka

A

A larger ka means a smaller pKa
PKa=-log

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33
Q

Is it better for a drug to have a bigger or smaller pKa

A

Since ionisisation helps drug dissolve a small pKa means the drug ionisizes quicker so smaller pKa is better

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34
Q

Calculating the ratio of dissociated to undissociated

A

Ibuprofen example;

Ibuprofen has a pKa of 4.4, it dissociates to release a proton. What is the ratio of dissociated:undissociated

Given pKa = 4.4, we calculate Ka:
• Ka = 10-pka
• Ka = 10-44 ~ 3.98 × 10-5
• Using the dissociation equation:
(buH]
• Assume pH = pKa (simplifies the calculation, meaning at pH 4.4, we have a 1:1 ratio)
• This means the concentrations of (H*| and [Ibu l are equal.
• Resulting Ratio:
• Since Ka ~ 4 × 10-5 and we assume the denominator IbuH) is 1 for simplicity:
• The ratio of dissociated (ionized) to undissociated (non-ionized) ibuprofen is approximately 4 × 10-5: 1.

35
Q

What is solubility?

A

The maximum drug that will dissolve in a given solvent at a given temperature and pressure
If a solute has an affinity for two solvents it will partition between them to reach an equilibrium,this is known as the partition co efficient

36
Q

How to measure solubility

A

• Add excess drug to a known volume of solvent at a given temperature and pressure
• Stir for a period of time sufficient to ensure all possible drug
• has dissolved
• Filter off excess solid drug
• Measure concentration of drug using Beer plot

37
Q

Beer lambert analysis

A

Beers law is how much light is absorbed based on the concentration of a solution

38
Q

Beer lambert equation

A

A= E.c.l

A=absorbance (so how much light is being absorbed by a substance, higher absorbance means more light is absorbed)
E= molar absorptivity (how well the substance absorbs light at a specific wavelength )
C= concentration (how much substance is in the solution)
L= path length (distance the light travels through the solution)

39
Q

Example

A

Sure, here’s the summary:

  1. Find λmax: Determine the wavelength at which your substance absorbs the most light.
  2. Measure Absorbance: Measure the absorbance of the saturated solution at λmax.
  3. Dilution (if needed): If the absorbance is too high, dilute the solution and measure again. Keep track of how much you dilute it.
  4. Compare with Calibration Plot: Use the calibration plot to determine the concentration of the solution based on its absorbance.
  1. Find λmax:
    • You find that your substance absorbs the most light at 500 nm.
  2. Measure Absorbance:
    • You measure the absorbance of the saturated solution at 500 nm and get an absorbance of 2.5.
  3. Dilution:
    • The absorbance is too high, so you dilute the solution by mixing 1 part of the solution with 9 parts of water (10 times dilution).
    • You measure the absorbance of the diluted solution and get an absorbance of 0.25.
  4. Compare with Calibration Plot:
    • Using the calibration plot, you find that an absorbance of 0.25 corresponds to a concentration of 0.1 M.
    • Since you diluted the solution by a factor of 10, the original concentration is ( 0.1 \text{ M} \times 10 = 1.0 \text{ M} ).
40
Q

Partition coefficient

A

P o/w is called the octanol partition coefficient
Can be defined as water/oil- defines how much a substance likes to be in oil compared to water
Greater p o/w means the substance prefers oil phase over the water phase greater affinity for oil phase.

To measure:
Mix known volumes of water and octanol
Add a known amount of drug
Stir to allow the drug to reach equilibrium between two phases
Separate the phases
Sample the aqueous phase an measure its absorbance

41
Q

Octanol

A

Alternatives to octanol to measure partition coefficients is isobutanol. Also computer programs like clogP programmes can predict it based on the molecular structure of a substance

Octanol and water form separate layers in a mixture but small amount of water can dissolve in octanol creating a hydrated state

42
Q

Improvement of solubility

A

Drugs formulated near their solubility limit may precipitate upon storage, strongly ionised drugs are very soluble and unionised drugs need careful formulation
Way to improve this is to convert a drug to an ionised form i.e. form the drug salt
You can also add a substituent

43
Q

Adding solubilisers to improve solubility
(MICELLE EXAMPLE)

A

Micelle is a surfactant which can be added to a solution. Has a polar head and non polar tail. Hydrophobic drugs can dissolve in the core
If the solvent is non polar it is possible to form inverted micelles
The more surfactant you add the more the solubility will increase until you reach a stop

44
Q

Cyclodextrins

A

Is an alternative to surfactants they are rings of glucose molecules with a hydrophobic core (CH2 groups)

45
Q

Emulsifiers

A

Emulsion is a stable dispersion of one liquid in a second immiscible liquid e.g. oil dispersed in water
Largest group of emulsifying agents is soaps and detergents and other compounds who’s basic structure s polar head and long organic tail
Creams and lotions include an emulsifier to make sure the formulation is stable and consistent.

46
Q

What is parenterals?

A

It’s any formulation that delivers the drug to the site of action but bypasses the gi tract
More time injection

47
Q

Injections

A

Thee are 3 types
Intravenous, intramuscular and subcutaneous

48
Q

Intravenous

A

Fastest way to deliver fluids and medication around the body,
Hollow needle passes through the skin directly into the vein. Any identifiable vein can be used. Peripheral if cant be left in the vein permanently because there is a risk of insertion site infection sepsis.

49
Q

Advantages of peripheral IV:

A

• It can deliver fluids that would be overly irritating to peripheral veins.
• Medications reach the heart immediately, and are quickly distributed to the rest of the body.
Multiple medications can be delivered at once even if they are not chemically compatible.

50
Q

IV therapy

A

It’s a continuous infusion of fluids with or without medication
Could be to correct dehydration, deliver medication or for a blood transfusion
• There are two types of fluids that are used for intravenous drips; crystalloids and colloids.
• Colloids contain larger insoluble molecules, such as gelatin or blood.

51
Q

Risk with Iv

A

• Infection
• Phlebitis
• Infiltration
• Fluid overload
• Electrolyte imbalance
• Embolism
• Drug salting out
• Drug-packaging interactions

52
Q

Advantages and disadvantages of IV

A

Advantages
• Rapid to site of action
• High level of dose control
• Can be stopped at any time

DisAdvantages of IV:
• Cost
• Requires qualified personnel
• Not favoured by patients
• Medical complications

53
Q

Intramuscular injections:

A

Subcutaneous region has. Good supply of capillaries but no lymph vessels in muscles
• Drugs diffuse through tissue and pass through capillary walls to enter circulation.
• Drug absorption proceeds by passive diffusion therefore it is a first order process

54
Q

Rate of absorption

A

dC = -kaC
dt
• Where ka is the 1st order rate constant and the half life of the absorption process is
t1/2 = 0.693/ka
• Drug absorption is 90% complete when a time equivalent to three times the half life has elapsed.

55
Q

Q: What are the important parameters in defining the bioavailability of drugs by the intramuscular route?

A

Both dissolution and diffusion are important parameters in defining bioavailability of drugs by this route.

56
Q

What are the important parameters in defining the bioavailability of drugs by the intramuscular route?

A

Both dissolution and diffusion are important parameters in defining bioavailability of drugs by this route.

57
Q

How do soluble, neutral drugs disperse from intramuscular sites?

A

: Soluble, neutral drugs disperse from intramuscular sites according to size.

Smaller molecules like mannitol rapidly diffuse, whereas larger molecules like insulin diffuse slower.

58
Q

Through which type of walls do drugs tend to move from intramuscular sites, and why is this significant?

A

Drugs tend to move through capillary walls rather than lipid walls, and this movement is usually the rate-limiting step.

59
Q

How does lipid solubility affect drug absorption from intramuscular sites?

A

Lipid-soluble drugs are generally absorbed faster than hydrophilic drugs.

60
Q

What effect does binding to muscle protein have on the absorption of hydrophilic drugs?

A

Hydrophilic drugs may bind to muscle protein, which delays but prolongs their action.

61
Q

Why might drug precipitation occur at the site of an intramuscular (i.m.) injection?

A

Because muscle tissue is more acidic than normal fluids, leading to drug precipitation, which can cause pain at the injection site.

62
Q

What are the three most commonly used sites for intramuscular (IM) injections?

A

The deltoid muscle on the upper arm, the quadriceps muscle group of the upper leg, and the gluteus muscles.

63
Q

What factors determine the most appropriate site for an IM injection?

A

The patient’s muscle density at each site, the type and nature of medication, and the patient’s preferred site for injections

64
Q

How can blood flow affect drug absorption from IM injections?

A

Reduced blood flow to muscle, due to age or disease states, can influence drug plasma levels.

65
Q

How does the formulation of diazepam affect its absorption from IM injections?

A

Valium, containing diazepam, has low plasma levels due to drug precipitation at the injection site, while Diapam, with a surfactant, has higher plasma levels.

66
Q

What layer of skin is a subcutaneous injection administered into?

A

The subcutis, the layer of skin directly below the dermis and epidermis.

67
Q

What medications are commonly administered via subcutaneous injections?

A

Vaccines, insulin, and morphine.

68
Q

Where on the body are suitable sites for subcutaneous injections?

A

The outer area of the upper arm, just above and below the waist, just behind the hip bone, and the front of the thigh.

69
Q

What are the advantages of subcutaneous injections?

A

Self-medication, ideal for drugs not stable or absorbed in the GI tract, and fast onset of action.

70
Q

What are the disadvantages of subcutaneous injections?

A

More risky self-medication, risk of infection or air bubbles, and more costly than oral formulations.

71
Q

What are the steps for administering a subcutaneous injection?

A
  1. Select site for injection
  2. Clean the site
  3. Insert syringe and administer medicine
  4. Remove syringe, wipe site if necessary, and dispose of syringe carefully.
72
Q

How does the formulation of insulin affect its absorption from subcutaneous injections?

A

Modifying insulin’s crystallinity can control solubility and duration of activity; for example, protamine-zinc insulin forms an amorphous precipitate at pH 7.

73
Q

What is a key characteristic of recombinant human insulin analogues like insulin lispro?

A

They have chemical modifications that create hexamers, which dissociate to monomers on injection, giving a faster onset of action.

74
Q

: Why is subcutaneous administration advantageous for methotrexate in treating rheumatoid arthritis?

A

It improves bioavailability and tolerance, reduces side effects, sustains treatment, and enhances patient independence.

75
Q

What are some other medications commonly given by injection and their routes

A

Vitamin K (IM), steroids (epidural), pethidine (IV, IM, SC), and adrenaline (IV, IM, SC, or directly into the heart).

76
Q

Types of catalysts

A

Homogenous catalysts- catalysts is in the same phase as the reactants
Heterogenous catalysts- catalyst is in different phase to the reactants
Autocatalysis:- catalyst is one of the products of the reaction (so when the catalyst is made the reaction rate increases automatically)

77
Q

Calorimetry

A

When energy change is measured by measuring power change

78
Q

Determining the melting point

A

Preformulation
In a melting tube take crystals and heat it up and watch them melt to get a range of melting points

79
Q

Determining enthalpies by changing the R group

A

To do this you need to change the r groups on the compound and then hydrolyse to see which r group the drug is most stable w

80
Q

True partition

A

A true apparent co efficient doesn’t consider the ionised species whereas an apparent does
If partition coefficient is equal to greater than one its a organic phase proffered
If its smaller than one then aqueous phase preffered

81
Q

What factors depend on the light absorbed

A

Width of the curvette
Wavelength of light
Sample concentration

82
Q

What are the advantages of solubility?

A

Is qualitative so can help tell which drug is present
Is quantitative, so can help you tell how much drug is present

83
Q

Describe how surfactants aids formulations containing hydrophobic drugs

A

Surfactants aid the formulation of hydrophobic drugs as they increase the
solubilisation by forming micelles. Hydrophobic drugs have low aqueous solubility,
limiting the concentration that can be achieved in solution. If a solution is close to its
limit it will precipitate out upon storage. With micelles present the drug can exist
inside the hydrophobic core thus dramatically increasing solubility. However, all
micelles have a maximum concentration and are therefore also limited in their scope.

Formulating Medicine And Compounds (8 decks)

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