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Geriatric hair and scalp disorders
Published in Robert A. Norman, Geriatric Dermatology, 2020
Acute herpes zoster antiviral treatment has changed in recent years. The efficacy of valacyclovir, the prodrug of acyclovir, and that of famciclovir137, the prodrug of penciclovir, have been documented in large clinical trials138,139. Both drugs are effective on herpes zoster-associated pain and in shortening the course of the disease. Development of resistance against acyclovir and the nucleoside analogs in the treatment of immunocompetent individuals has not become a problem. Famciclovir and valacyclovir allow for less frequent daily dosing and higher concentrations of serum drug concentration. Initiation of therapy as soon as possible is advised. Famciclovir, 500 mg t.i.d. for one week, and valacyclovir, 1 g t.i.d. for one week are the recommended dosages. Prednisone in cases of trigeminal involvement has been shown to be beneficial140,141.
Drug Therapy in Otology
Published in John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie, Basic Sciences Endocrine Surgery Rhinology, 2018
Aciclovir may be administered orally at a dosage of 800 mg five times a day for 5 days. If treatment is commenced prior to 72 hours after the onset of the rash, acyclovir may shorten the rash duration and acute symptoms and reduce the incidence of post-herpetic neuralgia.22 Aciclovir should be used with caution in patients with renal impairment or who are pregnant or breastfeeding. Side effects include nausea, vomiting, gastrointestinal disturbances, rash, photosensitivity and, rarely, hepatitis, acute renal failure and neurological reactions. Two newer antiviral agents are famiclovir (a prodrug of penciclovir) and valaciclovir (an ester of aciclovir), which, depending on indication and co-morbidities, are administered up to three times a day (see British National Formulary1 for further details).
Famciclovir and Penciclovir
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
Zeena Nawas, Elmira Ramos, Jarad Peranteau, Larry Tong, Stephen K. Tyring
The antiviral agent penciclovir is a synthetic acyclic guanine analog that inhibits the replication of several herpesviruses. Structurally, it is very similar to aciclovir; however, these two drugs differ in pharmacokinetics and antiviral effects (Tyring, 1998). Penciclovir (9-(4-hydroxy-3-hydroxymethylbut-1-yl) guanine) has poor oral absorption, which led to the development of famciclovir (2-[2-(2-amino-9H-purin-9-yl)ethyl]-1,3-propanediol diacetate), a penciclovir prodrug with enhanced bioavailability. When administered orally, famciclovir is readily absorbed and thereafter rapidly metabolized to penciclovir, resulting in therapeutic blood levels of the latter. Penciclovir inhibits herpesvirus replication by selectively inhibiting herpes-viral DNA polymerase without affecting mammalian DNA polymerases. Famciclovir is approved in most countries for treatment of infections due to herpes simplex and varicella-zoster viruses.
Possible therapeutic agents for COVID-19: a comprehensive review
Published in Expert Review of Anti-infective Therapy, 2020
Khaled Mosaad Elhusseiny, Fatma Abd-Elshahed Abd-Elhay, Mohamed Gomaa Kamel
Of note, penciclovir was one of the first agents that were evaluated against SARS-CoV-2. It is usually used against herpes viruses as it is a guanosine analogue that inhibits herpes DNA polymerase enzyme, consequently, it inhibits virus replication. The in vitro study done by Wang et al. assessed the efficacy of penciclovir against isolates of SARS-CoV-2. Penciclovir was found to have a half-maximal effective concentration (EC50) = 95.96 μM; indicating a relatively low efficacy against SARS-CoV-2 [16,26]. Another group of researchers found that penciclovir could effectively inhibit the RNA-polymerase of SARS-CoV-2, suggesting that it may have the potential to be further investigated in clinical trials [35]. However, penciclovir is not absorbed well when taken orally. Moreover, there is limited evidence regarding its safety in pregnancy and breastfeeding with headache and nausea as the most common side effects [36].
In vitro studies with two human organic anion transporters: OAT2 and OAT7
Published in Xenobiotica, 2018
Sumathy Mathialagan, Chester Costales, Laurie Tylaska, Emi Kimoto, Anna Vildhede, Jillian Johnson, Nathaniel Johnson, Takami Sarashina, Kenta Hashizume, Caleb D. Isringhausen, Lydia M. M. Vermeer, Andrea R. Wolff, A. David Rodrigues
Currently, there are no reports describing methods supporting measurement of OAT7 activity in human primary hepatocytes. Even for OAT2, only probenecid-inhibitable PAH and bromosulfophthalein (BSP)-inhibitable entecavir uptake has been reported (Furihata et al., 2017; Jigorel et al., 2005; Le Vée et al., 2015). Therefore, we sought to include a well characterized single donor PHH preparation in the current study, employing both penciclovir and E3S as substrates. It is understood that OAT2 protein expression and activity in isolated primary human hepatocytes can vary up to 10-fold across organ donors (Le Vée et al., 2015; Vildhede et al., 2015). In our hands, PHH-mediated uptake of penciclovir was evident, inhibited by ketoprofen (91%), and characterized by an IC50 (27.2 μM) similar to that of transfected OAT2-tv1 (23.1 μM) not OAT7 (Table 2). Therefore, it is concluded that OAT2 plays a major role in the PHH-mediated uptake of penciclovir. In agreement, the penciclovir uptake ratio (35 versus 2.6) and REF (0.20 versus 0.13) is higher for OAT2 compared to OAT7 (Table 1, Figure 2(C)). Moreover, uptake of penciclovir (∼1 µM) was not evident with other hepatic SLCs (Supplemental Table 2), and there was no inhibition of its PHH-mediated uptake by OATP-selective RIFsv (20 µM).
Review for Disease of the Year: Varicella Zoster Virus-Induced Anterior Uveitis
Published in Ocular Immunology and Inflammation, 2018
Ilknur Tugal-Tutkun, Luca Cimino, Yonca Aydin Akova
All patients with acute HZO should receive antiviral therapy in order to shorten the course of the disease and reduce the frequency and severity of ocular complications. The treatment of acute HZO infection with oral acyclovir 800 mg five times daily, valacyclovir 1000 mg three times daily, or famciclovir 500 mg three times daily for 10 days, given within 72 hours of the onset of symptoms reduces the incidence and severity of anterior uveitis 32,33,50–52 Valacyclovir, a prodrug of acyclovir and famciclovir, a prodrug of penciclovir, with improved bioavaliability, have both been shown to be equivalent in HZO treatment. In general, these drugs are safe and well tolerated. Because of dosing advantages, valacyclovir and famciclovir may be preferred to acyclovir for the treatment of HZO. 52,53 A dose adjustment may be required in patients with renal insufficiency.