SIMULASI PERHITUNGAN KINETIKA REAKSI | STABILITAS OBAT - STFI Bandung

Summary

This video explains the process of calculating the stability of pharmaceutical drugs using kinetics and reaction rate constants. The focus is on determining T90, the time it takes for a drug's concentration to degrade to 10% of its initial value. Key steps include calculating rate constants at various temperatures (70°C, 80°C, 90°C), using the Arrhenius equation to adjust these for 25°C, and applying linear regression in Excel for data analysis. The video concludes with converting the calculated T90 into practical units like days, months, and years, providing insight into a drug's expiration and storage stability.

Takeaways

• 😀 T90 represents the time needed for a drug's concentration to degrade to one-tenth of its initial value, indicating the shelf-life of a pharmaceutical product.
• 😀 The formula to calculate T90 is: T90 = 0.105 / k, where k is the reaction rate constant.
• 😀 The rate constant k at 25°C can be calculated using the concentration values over time, typically derived from experimental data.
• 😀 For experiments at different temperatures (70°C, 80°C, 90°C), the rate constants must be adjusted to a standard temperature of 25°C for comparison.
• 😀 The Arrhenius equation is used to adjust rate constants between temperatures: k = A * e^(-Ea/RT), where Ea is the activation energy, and T is the temperature in Kelvin.
• 😀 Activation energy (Ea) is crucial for calculating the rate constant at 25°C and can be determined from a graph of ln(k) versus 1/T.
• 😀 A standard curve (calibration curve) is created by plotting concentration against time, and a linear regression is used to determine the relationship.
• 😀 Once the concentrations at different time intervals are determined, the rate constants for each temperature are calculated and then converted to k25 for standard conditions.
• 😀 To convert experimental data to temperature-adjusted values, Excel can be used for linear regression and data analysis, ensuring accurate calculations.
• 😀 The final T90 value can be converted into practical units, such as minutes, days, months, or years, to represent the stability or shelf-life of the drug.

Q & A

What is the purpose of calculating the T90 value in drug stability testing?

The T90 value represents the time it takes for a drug's concentration to degrade to 10% of its initial value. It helps determine the shelf life or expiration time of a drug.

How is the T90 value calculated?

The T90 value is calculated using the formula: T90 = 0.105 / k, where 'k' is the reaction rate constant, which varies depending on the temperature and other factors.

Why is the reaction rate constant (k) at 25°C commonly used in drug stability testing?

The reaction rate constant at 25°C is used because it corresponds to room temperature, which is the typical condition under which drugs are stored and tested.

How do you calculate the rate constant (k) at 25°C using experimental data?

To calculate k at 25°C, you need to first calculate the rate constants at other temperatures (e.g., 70°C, 80°C, 90°C) and then use these values in an equation that involves activation energy (Ea) and the temperature to estimate k at 25°C.

What role does Microsoft Excel play in calculating drug stability constants?

Microsoft Excel is used to create regression graphs and calculate various constants like the rate constant at different temperatures, which are essential for determining the drug's stability.

What is the significance of the regression analysis in drug stability testing?

Regression analysis is used to establish a relationship between time and concentration. It helps in deriving the necessary formulas and constants needed for calculating the rate of degradation and ultimately, the drug's stability.

What is the process of converting experimental data from different temperatures into the rate constant at 25°C?

The data from different temperatures (e.g., 70°C, 80°C, and 90°C) are used to calculate individual rate constants for each temperature. These constants are then used in an equation involving activation energy to calculate the rate constant at 25°C.

How do you determine the activation energy (Ea) from the experimental data?

The activation energy is determined by plotting the natural logarithm of the rate constants against the inverse of the temperature in Kelvin. The slope of this line provides the value for Ea, which is used in further calculations.

What is the formula for calculating the rate constant at a given temperature using activation energy?

The formula is: k = A * exp(-Ea / RT), where k is the rate constant, A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin.

Once the rate constant at 25°C is known, how do you calculate the T90 value?

The T90 value is calculated by dividing 0.105 by the rate constant at 25°C (k25). This gives the time required for the drug concentration to degrade to 10% of its original value.