Some important interactions between drugs at shared sites of action and/or therapeutic effect
Hugh Mcgavock in Pitfalls in Prescribing and How to Avoid Them, 2017
An excellent way of grasping this basic concept is to remember how often we co-prescribe two or more potent drugs to in order to 'normalise' pathophysiology. Everyday examples include the following: Doctors are well aware of such synergistic prescribing, which includes the treatment of asthma, type 2 diabetes and hyperlipidaemia. It is worth revising several important adverse drug interactions in treatment regimens for cardiovascular disease, asthma and the specialist-led treatment of depression and psychosis. As showed, in regimens for hypertension and congestive heart failure (CHF), NSAIDs will cause significant deterioration of control. A ‘wonder-drug’ group now widely available without prescription is the erection enhancer’s sildenafil, tadalafil and vardenafil. As showed, men who are using an erection enhancer should not take grapefruit juice, grapefruit or bitter oranges, as they increase the bioavailability of the erection enhancers.
Clinical pharmacology (and toxicology and therapeutics)
Shibley Rahman, Avinash Sharma in A Complete MRCP(UK) Parts 1 and 2 Written Examination Revision Guide, 2018
This chapter details what is required in terms of competencies, skills and knowledge from junior physicians in core medical training in clinical pharmacology. Lithium is a mood-stabilising drug used most commonly prophylactically in bipolar disorder but also as an adjunct in refractory depression. It has a very narrow therapeutic range and a long plasma half-life, being excreted primarily by the kidneys. Sildenafil is a phosphodiesterase type V inhibitor used in the treatment of impotence. Sulphonylureas are oral hypoglycaemic drugs used in the management of type 2 diabetes mellitus. They work by increasing pancreatic insulin secretion and hence are only effective if functional B cells are present. Sodium valproate is used in the management of epilepsy and is first-line therapy for generalised seizures. It works by increasing GABA activity. Hormone replacement therapy (HRT) involves the use of a small dose of oestrogen to help alleviate menopausal symptoms.
Drugs That Treat Sexual Dysfunction
Robert B. Raffa, Patricia J. Bush, Albert I. Wertheimer in How Prescription and Over-the-Counter Drugs Affect Sexual Performance, 2021
The blockbuster drug Viagra was originally developed in 1989 by Peter Dunn and Albert Wood at Pfizer as an antihypertensive that could possibly treat angina, or chest pain, which occurs when the vasculature serving the thoracic cavity constricts and blood flow is markedly reduced. Dunn and Wood sought to develop a new heart medication that would relax blood vessels and improve blood flow. In popular stories, it is often claimed that the scientists at Pfizer had no idea about the drug’s side effects or its potential to improve sexual performance, but that is not entirely correct. In fact, the scientists working on this new heart drug had already found out that vasodilatation occurred throughout the body and that the drug they were working on, sildenafil citrate, might have other applications including improving blood flow to the penis, and could therefore treat erectile dysfunction.
Enhanced dissolution of sildenafil citrate as dry foam tablets
Published in Pharmaceutical Development and Technology, 2019
Somchai Sawatdee, Apichart Atipairin, Attawadee Sae Yoon, Teerapol Srichana, Narumon Changsan
Dry foam formulation technology is alternative approach to enhance dissolution of the drug. Sildenafil citrate was suspended in sodium dodecyl sulfate solution and adding a mixture of maltodextrin and mannitol as diluent to form a paste. Sildenafil citrate paste was passed through a nozzle spray bottle to obtain smooth foam. The homogeneous foam was dried in a vacuum oven and sieved to obtain dry foam granules. The granules were mixed with croscarmellose sodium, magnesium stearate and compressed into tablet. All formulations were evaluated for their physicochemical properties and dissolution profiles. All the tested excipients were compatible with sildenafil citrate by both differential scanning calorimetry (DSC) and infrared (IR) analysis. There are no X-ray diffraction (XRD) peaks representing crystals of sildenafil citrate observed form dry foam formulations. The hardness of tablets was about 5 kg, friability test
The contribution of sildenafil (Viagra) to ovarian stimulation with gonadotropins in a woman with poor ovarian response
Published in Gynecological Endocrinology, 2014
Eftihios Trakakis, Vassilios Vaggopoulos, Vasileios D. Sioulas, Periklis Panagopoulos, Ioannis Grammatikakis, Peny Ambatzi, Dimitrios Kassanos
We aim to present the first case of a pregnancy achieved by administering sildenafil (Viagra) to a woman not responding to controlled ovarian hyperstimulation (COH) with the sole use of gonadotropins. A 37-year-old woman underwent COH, as part of an intracytoplasmic sperm injection (ICSI) cycle, with the combination of r-FSH and HMG for 13 d, without evidence of follicular growth. The addition of oral sildenafil at a dose of 50 mg per day for a total of five doses improved the ovarian response and resulted in the retrieval of 10 oocytes. Three embryos were transferred to the uterine cavity resulting in a successful pregnancy and, eventually, the delivery of a healthy neonate. Conclusively, the use of sildenafil as an adjunct to COH protocols may enhance ovarian response in a woman with poor ovarian response (POR) and merits further research.
Oral bioavailability and pharmacokinetics of sildenafil citrate dry foam tablets in rats
Published in Cogent Medicine, 2018
Somchai Sawatdee, Apichart Atipairin, Attawadee Sae Yoon, Teerapol Srichana, Narumon Changsan, Tan Suwandecha, Wirot Chanthorn, Atchara Phoem
Sildenafil has low water solubility and oral bioavailability. Dry foam formulations of solid dosage forms of poorly water-soluble drugs may exhibit improved dissolution and bioavailability. We previously developed a sildenafil citrate dry foam tablet formulation and found that it had an improved dissolution profile. In this study, we investigated the pharmacokinetic parameters of sildenafil dry foam tablets in rats after oral administration (at a dose equivalent to 20 mg/kg of sildenafil) and compared them with those of commercial sildenafil tablet and dry powder formulations. LC/MS/MS analysis of plasma sildenafil concentration revealed that the AUCs of sildenafil and N-desmethyl sildenafil in the sildenafil citrate dry foam tablet group were significantly higher (150% and 110%, respectively; P