Age is a key factor underlying the determination of dosing for many drugs. It is obvious that there exist developmental factors that affect the dosage. These factors range from body size, adaptation, tolerance and tissue complexity. Also, other factors such as drug administration time and route, treatment required, gender affect dosage. These factors, therefore, lead to variations in the dosage prescription. Although all these factors affect the effectiveness of drugs actions, I will describe the effects derived from the aspect of age and disease state. In a bid to perform this task, I will make an intimate enumeration and evaluation concerning the impacts of age and disease state on fentanyl dosing. Fentanyl sensitivity is higher in older patients than younger patients. However, dosage preference differs on a wide range due to these factors. For instance, a forty-year-old patient suffering from severe hepatic impairment may possess a double sensitivity to fentanyl compared with sixteen years old patient suffering a similar problem. However, this is not always the scenario. In some cases, certain diseases and operations call for variations in prescriptions. Patients undergoing surgical procedures such as transplantation cannot receive similar dosing with patients undergoing mild treatment (Lehmann 1991). Research performed in1982 implied that the degradation of fentanyl was low in an older patient. This depicted the clinical effectiveness of fentanyl in old patients than in young patients. Other demonstrations have shown a decreasing dosage with an increase in age (50% decrement from twenty to eighty-nine years). When undergoing the minor procedure, children between the age of 1 and 12 years require doses of one to two micrograms per kilogram at intervals of a half minute and one minute. Also, opioid-tolerant children above two years old can receive initial doses of twenty-five micrograms hourly (Cote, Jerrold & Tedros 2009). Children above twelve years old and adults use lower doses of 0.5 to 1 microgram/kilogram/hour to sedate minor operations. Major procedures, however, require a higher dosage of 25-50 micrograms repeat after every five minutes (McPherson 2010). The nasal application of fentanyl is only used by cancer suffering patients above the age of eighteen years. Patients who are above sixty-five years should use fentanyl under strict caution because they show many side effects. These arguments support and purport that fentanyl administration and performance are dependent on age. Different diseases have varying requirements for drug administration. Some diseases depict a higher need for the concentration of the drug while others show requires low concentrations to reach clinical effect. For instance, patients with cancer, renal and hepatic diseases show differences in sensitivity to fentanyl. The liver metabolizes fentanyl into norfentanyl at the initial stages. If this metabolism fails, fentanyl remains in the body and performs untargeted roles that affect the system adversely. These characteristics of drug non-clearance are evident in patients with uremia. The patients depict reduced fentanyl clearance rates. The reduction results in the depression of respiration. Adjustments are