1. Atovaquone is a potent antiprotozoal slowly and irregularly absorbed after administration as tablets to fasting volunteers. A series of studies was performed to investigate the effects of food, bile and formulation on atovaquone absorption. 2. In 18 healthy male volunteers, a high‐fat breakfast administered 45 min before 500 mg atovaquone as tablets increased AUC by 3.3‐fold (95% CI 2.8‐4.0) and Cmax 5.3‐fold (4.3‐6.6) compared with fasting. 3. The absorption of atovaquone from tablets was examined in 12 healthy male volunteers after an overnight fast, following toast alone, toast with 28 g butter (LOFAT), or toast with 56 g butter (HIFAT). Compared with absorption when fasted, toast had no significant effect but LOFAT increased AUC 3.0‐fold (2.1‐4.2) and Cmax 3.9‐fold (2.6‐5.8). HIFAT increased AUC 3.9‐fold (2.7‐5.5) and Cmax 5.6‐fold (3.8‐8.4). 4. The absorption of atovaquone was examined in nine healthy fasting male volunteers from tablets, an aqueous suspension, and an oily solution/suspension in miglyol (fractionated coconut oil). Compared with tablets, AUC following the aqueous suspension was increased 1.7‐fold (1.0‐2.7) and Cmax 2.4‐fold (1.7‐ 3.5). Following miglyol, AUC was increased to the same extent but Cmax was only increased 1.8‐fold (1.2‐2.6). 5. Atovaquone absorption was examined in eight healthy fasting male volunteers following an i.v. infusion of cholecystokinin octapeptide (CCK‐OP) which decreased gallbladder volume by 82% (73%‐90%) on occasion 1 or saline on occasion 2. AUC(0,12) was increased following CCK‐OP by 1.6‐fold (1.1‐2.4) and Cmax by 1.5‐fold (0.98‐2.4).(ABSTRACT TRUNCATED AT 250 WORDS)

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This review addresses the pharmacokinetics and pharmacodynamics of transdermally delivered drugs. The systemic input of drugs via the skin has attracted considerable interest over the past 15 years. The early promise of the administration route has, to some extent, been realised with the approval and successful launching of transdermal formulations of hyoscine (scopolamine), glyceryl trinitrate (nitroglycerin), clonidine and oestradiol. The further application of transdermal delivery, however, will require additional effort. While other molecules (e.g. testosterone, fentanyl, nicotine) may ultimately be administered in this way, important questions pertaining to pharmacology (tolerance), toxicity (irritation, sensitisation) and dose sufficiency (penetration enhancement) remain. These problems are illustrated using information which has been published in the literature. Overall, while the enthusiasm for attraction and benefits of transdermal delivery remain evident, it is clear that future successes will demand a heightened level of commitment and skill from the pharmaceutical scientist.