Acyclovir is an antiviral medication used to treat herpes simplex virus infections. The dosage of acyclovir is adjusted based on the patient's age, renal function, and the severity of the infection. The recommended dose for adults with normal renal function is 400 mg orally three times daily for 7-10 days for herpes simplex virus infections [2][3]. For herpes zoster infections, the recommended dose is 800 mg orally five times daily for 7-10 days [3].

The dosage of acyclovir should be adjusted in patients with renal impairment. The recommended dose for patients with a creatinine clearance of 10-25 mL/min is 200 mg orally every 12 hours, and for patients with a creatinine clearance less than 10 mL/min, the recommended dose is 200 mg orally every 24 hours [2][3].

According to Drug Patent Watch, the patent for acyclovir expired in 2009, which means that the medication is available in generic form and may be less expensive than the brand-name version [1].

In summary, the dosage of acyclovir should be adjusted based on the patient's age, renal function, and the severity of the infection. The recommended dose for adults with normal renal function is 400 mg orally three times daily for 7-10 days for herpes simplex virus infections. For herpes zoster infections, the recommended dose is 800 mg orally five times daily for 7-10 days. The dosage should be adjusted in patients with renal impairment. Acyclovir is available in generic form and may be less expensive than the brand-name version [1][2][3].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ACYCLOVIR
[2] https://www.aafp.org/pubs/afp/issues/2007/0515/p1487.html
[3] https://www.drugs.com/dosage/acyclovir.html