Aim: Study of effect of hepatic microsomal enzyme inducers on the phenobarbitone sleeping time in mice.
Reference:
Thomas N. Thompson & Curtis D. Klaassen. The Effects of Hepatic Microsomal Enzyme Inducers on the Pharmacokinetics of Ouabain after Portal and Systemic Administration to Rats. Journal of Pharmacy and Pharmacology, Vol. 47, Issue 12A, December 1995, pp. 1041–104
Introduction:
Hepatic microsomal enzyme inducers are compounds that enhance the activity of liver enzymes, especially those belonging to the cytochrome P450 system. These enzymes play a vital role in drug metabolism, and their induction can significantly alter the pharmacokinetics of various drugs. This study evaluates how pre-treatment with enzyme inducers affects the onset and duration of phenobarbitone-induced sleep in mice, providing insights into drug-drug interactions and metabolic modulation.
Materials and Equipment:
Animals: Healthy adult mice (20–30 g)
Chemicals & Drugs: Phenobarbitone sodium (hypnotic agent), Phenobarbital (enzyme inducer), Rifampicin (enzyme inducer), Normal saline (control)
Instruments & Equipment: Syringes and fine needles, Stopwatch or digital timer, Animal cages, Weighing balance, Animal restraining and housing apparatus
Method:
1. Animal Preparation:
Healthy adult mice were acclimatized for at least one week under standard laboratory conditions. They were randomly divided into three groups with six animals each:
- Group I: Control (received saline)
- Group II: Phenobarbital-treated
- Group III: Rifampicin-treated
2. Pre-Treatment with Enzyme Inducers:
For seven consecutive days, Groups II and III were administered enzyme inducers intraperitoneally:
- Phenobarbital: 80 mg/kg/day (Group II)
- Rifampicin: 50 mg/kg/day (Group III) Group I received an equivalent volume of saline.
3. Phenobarbitone Administration:
On the eighth day, all animals from all groups received phenobarbitone sodium (50 mg/kg, i.p.) to induce sleep.
4. Observation and Recording:
After phenobarbitone administration, mice were placed in individual cages and observed carefully.
- The onset of sleep was recorded as the time from injection until the mouse lost its righting reflex (inability to turn back when placed on its back).
- The duration of sleep was recorded as the time taken to regain the righting reflex.
All data were documented accurately for analysis.
Observations (Sample Data):
| Group | Time to Onset of Sleep (min) | Duration of Sleep (min) |
| Control | 10 ± 2 | 120 ± 10 |
| Phenobarbital | 8 ± 1 | 60 ± 5 |
| Rifampicin | 9 ± 1 | 65 ± 7 |
Note: These are reference values. Actual results may vary based on laboratory practice.
Interpretation of Results:
Control Group: Mice receiving saline showed an average onset of sleep at around 10 minutes with a sleep duration of approximately 120 minutes.
Phenobarbital Group: Mice pre-treated with phenobarbital exhibited a faster onset of sleep (8 minutes) and a significantly reduced sleeping duration (60 minutes). This suggests enhanced metabolic breakdown of phenobarbitone due to induced liver enzymes.
Rifampicin Group: Similarly, rifampicin pre-treatment led to a reduced sleep duration (65 minutes) and earlier onset (9 minutes), indicating its effect as a potent enzyme inducer.
Conclusion:
The experiment confirms that hepatic microsomal enzyme inducers like phenobarbital and rifampicin significantly reduce the sleeping time induced by phenobarbitone in mice. This reduction is due to enhanced metabolism and faster clearance of the hypnotic drug, highlighting the importance of enzyme induction in altering drug effects.
Precautions:
- Use proper dosing and accurate body weight measurements.
- Ensure sterility of injectable solutions.
- Handle animals gently and ethically throughout the procedure.
- Record data precisely and consistently.