From the Guidelines
The drop rate for a 7 kg boy receiving Phenytoin IV is 70 drops per minute is incorrect, the correct calculation is as follows: To calculate the drop rate, I first determined the total dose by multiplying the patient's weight (7 kg) by the prescribed dose (15 mg/kg), which equals 105 mg of Phenytoin 1. Since the medication is to be administered over 30 minutes, I needed to find the volume of solution containing this dose. Assuming a standard concentration of Phenytoin (typically 50 mg/mL), the total volume would be 2.1 mL (105 mg ÷ 50 mg/mL). With 1 mL equal to 20 drops, the total number of drops is 42 (2.1 mL × 20 drops/mL). Dividing this by the infusion time of 30 minutes gives a drop rate of 1.4 drops per minute. However, this calculation assumes a standard concentration - if using a different concentration or if the Phenytoin is diluted in a larger volume, the drop rate would need to be recalculated accordingly. It's essential to verify the concentration being used and adjust calculations as needed for safe administration. Some key points to consider when administering Phenytoin include monitoring for signs of toxicity, such as nystagmus, ataxia, and cardiac arrhythmias, as well as being prepared to provide respiratory support in case of apnea 1. Additionally, Phenytoin should be diluted in normal saline to avoid precipitation and is incompatible with glucose-containing solutions 1. Given the potential for adverse effects, it is crucial to closely monitor the patient's vital signs and adjust the infusion rate as needed. In the context of real-life clinical medicine, prioritizing the patient's safety and adjusting the administration protocol accordingly is essential. Some of the key considerations for Phenytoin administration, such as the risk of hypotension and arrhythmias, especially with rapid infusion, should be taken into account when determining the drop rate 1. The most critical factor in administering Phenytoin is ensuring the patient's safety and minimizing the risk of adverse effects. To achieve this, healthcare professionals should carefully calculate the drop rate, verify the concentration of the solution, and closely monitor the patient's vital signs throughout the infusion. By taking these precautions, the risk of adverse effects can be minimized, and the patient can receive the necessary treatment while maintaining the highest possible quality of life. In the event of any concerns or uncertainties, consultation with a cardiologist or other relevant specialist is strongly recommended 1. Ultimately, the goal of Phenytoin administration is to provide effective treatment while prioritizing the patient's safety and well-being. By following these guidelines and taking a cautious approach, healthcare professionals can ensure the best possible outcomes for their patients.
From the FDA Drug Label
The drug should be injected slowly intravenously at a rate not exceeding 1 to 3 mg/kg/min or 50 mg per minute, whichever is slower. A loading dose of 15 to 20 mg/kg of Phenytoin Sodium Injection intravenously will usually produce serum concentrations of phenytoin within the generally accepted serum total concentrations between 10 and 20 mcg/mL
To calculate the drop rate per minute for a 7 kg boy receiving 15 mg/kg of Phenytoin IV over 30 minutes, with 1 mL equal to 20 drops:
- Dose: 15 mg/kg x 7 kg = 105 mg
- Volume: Assuming 50 mg/mL concentration (as 50 mg phenytoin sodium per milliliter), the volume required is 105 mg / 50 mg/mL = 2.1 mL
- Time: 30 minutes
- Drop rate: 2.1 mL x 20 drops/mL = 42 drops, over 30 minutes
- Drop rate per minute: 42 drops / 30 minutes = 1.4 drops per minute 2, 2
From the Research
Calculation of Drop Rate per Minute
To calculate the drop rate per minute for a 7 kg boy receiving 15 mg/kg of Phenytoin IV over 30 minutes, we need to follow these steps:
- Calculate the total dose of Phenytoin: 15 mg/kg x 7 kg = 105 mg
- Since the study does not provide information on the concentration of the Phenytoin solution, we will assume a common concentration of 50 mg/mL 3.
- Calculate the total volume of the solution: 105 mg / 50 mg/mL = 2.1 mL
- Given that 1 mL is equal to 20 drops, calculate the total number of drops: 2.1 mL x 20 drops/mL = 42 drops
- Calculate the drop rate per minute: 42 drops / 30 minutes = 1.4 drops/minute
Relevant Studies
The provided studies do not directly address the calculation of drop rate per minute for Phenytoin administration. However, they do discuss the safety and efficacy of Phenytoin and its prodrug, fosphenytoin, in various clinical settings 4, 5, 6, 3, 7.
- A study from 1991 discusses the administration of Phenytoin by constant intravenous infusion, highlighting the importance of selective rates of administration to minimize adverse effects 3.
- Another study from 1983 evaluates the safety of administering Phenytoin sodium by intermittent intravenous infusion, concluding that careful infusion is safe when governed by approved written guidelines 7.