We want to investigate whether an acute administration of hydroxychloroquine sulphate affects hedonic food intake, appetite related sensations and gastrointestinal hormone release in overweight female subjects.

Intragastric administration of a quinine-solution has shown to decrease hedonic food intake in healthy female volunteers. The effect of a tablet containing hydroxychloroquine sulphate on hedonic food intake in overweight female individuals has not been studied to date. The primary outcome of the current study is to evaluate the effect of hydroxychloroquine sulphate on hedonic food intake, assessed by ad libitum food intake of a chocolate milkshake one hour after dosing. The study is a randomized, placebo-controlled, double blinded cross-over study. Forty overweight females will be recruited. An acute dose of 400 mg hydroxychloroquine sulphate will be administered. Blood samples will be collected at regular time points to measure gastrointestinal hormone release and whole blood glucose levels. Appetite-related sensations will be scored at regular time points on visual analog scales.

Inclusion Criteria:

• Subject is female between 18 and 65 years of age.
• Subject has a BMI between 25 and 30 kg/m² and has a stable body weight for at least 3 consecutive months at the start of the study and keeps a stable weight during the study visits.
• Subject is allowed to take 2 Plaquenil capsuls for one visit with a maximal dose of 6.5 mg hydroxychloroquine sulphate per kg bodyweight.
• Women of child-bearing potential agree to apply during the entire duration of the trial a highly effective method of birth control, which is defined as those which result in a low failure rate (i.e., less than 1% per year) when used constantly and correctly such as implants, injectables, combined oral contraceptive method, or some intrauterine devices (IUDs), sexual abstinence, or vasectomized partner. Women of non-childbearing potential may be included if surgically sterile (tubal ligation or hysterectomy) or postmenopausal with at least 2 year without spontaneous menses.
• Subject understands the study procedures and agrees to participate in the study by giving written informed consent.

Exclusion Criteria:

• Subject is under age of legal consent, male, pregnant or breastfeeding.
• Subject with a BMI ≤ 25 kg/m² or BMI ≥ 30 kg/m².
• Subject is on a diet to induce weight loss or any other treatment for obesity.
• Subject has current symptoms or a history of gastrointestinal or other significant somatic or psychiatric diseases or drug allergies.
• Subject has diabetes.
• Subject has a significant heart, lung, liver or kidney disease.
• Subject has a QT-interval > 450 ms.
• Subject has any history of a neurological disorder.
• Subject has a history of abdominal surgery. Those having undergone a simple appendectomy more than 1 year prior to the screening visit may participate.
• Subject has retinopathy.
• Subject suffers from psoriasis.
• Subject has porphyria.
• Subject shows abnormal eating behavior or has an eating disorder.
• History or current use of drugs that can affect glycaemia, gastrointestinal function, motility or sensitivity or gastric acidity.
• History or current use of centrally acting medication, including antidepressants, antipsychotics and/or benzodiazepines (in the last year before screening visit).
• Subject consumes excessive amounts of alcohol, defined as >14 units per week.
• Subject is currently (defined as within approximately 1 year of the screening visit) a regular or irregular user (including "recreational use") of any illicit drugs (including marijuana) or has a history of drug (including alcohol) abuse. Further, patient is unwilling to refrain from the use of drugs during this study.
• High caffeine intake (> 500 ml coffee daily or equivalent).
• Inability or unwillingness to perform all of the study procedures, or the subject is considered unsuitable in any way by the principal investigator.
• Recent participation (<30 days) or simultaneous participation in another clinical study.
• Subjects with lactose intolerance.
• Subjects with quinine allergy.

Female volunteers have a higher chance to be more sensitive for bitter compounds because of their genetic background in comparison to males.